Vibration-rotation spectrum of formaldehyde

JUUKNAL

UF MOLECULAR

SPECTROSCOPY

63, 485-508

Vibration-Rotation C-H TORU

Spectrum of Formaldehyde

Stretching

NAI(XAW’A,

(1976)

Fundamentals

KOICHI

YAMADA,'

Ileparfmenloj Cltemistry, Facdly

Hon,qo, Bunkyo-ku,

v1 and 1/S

AND Kozo

KUCHITW

oj Science, The Unicersit~ Tokyo 113, Japan

of Tokyo,

The infrared vibration-rotation spectrum of formaldehyde vapor has been measured in the region from 2600 to 3400 cm-’ with resolution from 0.04 to 0.07 cm-i. An extensive rotational analysis of the ~1 and Y; bands has confirmed and superseded the previous bandcontour analysis of a medium-resolution spectrum. A large number of subbranches of both the vi and Y$ bands are perturbed by the combination bands Ye + Q, Ye + ~1, and VP+ ~6, whereas the Coriolis interaction between ~1 and Y:,is weak. The following effective rotational constants (in cm-r) are obtained :

Y, = 2782.49(l),

.a, = 9.250(S),

& = 1.2968(6),

c, = 1.1321(L),

Y: = 2843.35(2).

;J, = 9.224(2),

& = 1.2936(L),

c, = 1.1303(l),

\vhere the number

given in parentheses

is three times the standard

error in the last digit.

I. INTRODUCTIOS

The spectra of formaldehyde HKO vapor have been investigated extensively in the microwave (l-4), infrared (j-12), and ultraviolet (12-13) regions because of their physical and chemical importance. In particular, the infrared spectrum of the C-H stretching band region was measured with medium resolution (-0.25 cm-‘) by Blau and Nielsen (5) to analyze the vg band in a symmetric-top approsimation and to locate the (j branch of the v1 band. Lately, a band contour analysis in the asymmetric-top scheme (8) displaced the vi band origin 16 cm-’ higher than Blau and Nielsen’s assignment. Nevertheless, the fine structures in this region had not been fully understood, and a further high-resolution study was desirable to resolve overlapping combination bands and clarify various interactions among them. Combination bands (Y”+ va, u:!+ ~6. V?+ vi, ~3 + ~6. and ~3 + v-1)and an overtone (2~3) are expected in the vicinity of the pi and ~6 fundamentals, as illustrated in Fig. 1. The strongest interactions expected among these bands are the a-type Coriolis interactions in the band pairs of v2 + ~6 and Y:!+ u I and ~3 + ~6and y3 + ~1, in parallel with that between the v6 and v4 fundamentals. where the coupling term is as large as IV s 10.3O.K cm-’ (5. 7). The u5 band can interact with the v2 f v6 and ~3 -I- ~6 bands through the Fermi resonances and ma!show an anomalous structure at high K (K 2 8) levels, where the coupled levels are ’ Present address: Giessen, Germany.

Physikalisch-Chemisches

Institut

485

der Justus

Liebig-Universitat

Giessen,

D-63

486

NAKAGAWA,

YAMADA

AND

KUCHITSU

loteracflon

types:

O. b. t : Coriolis F

0

type

b Me

band FIG.

(--)

: Fermi

c fYPe

type

1. Vibrational states in the C-H stretching band region and possible interactions among them observed states, (- - -) expected states.

predicted to cross one another. It is possible that the vr, band is also perturbed by accidental Coriolis interactions with ~1 and v2 + Ye.The v1 band, on the other hand, may also be perturbed by the vg, vz + VJ, and v3 + v6 bands through Coriolis interactions at particular K levels of accidental degeneracy. Hence, we have measured a high-resolution infrared spectrum in the range from 2600 to 3400 cm-‘. Our preceding paper (11) analyzed the high-wavenumber part of this spectrum to determine the v2 f vs and ZJZ+ v6 band parameters. The present paper reports on an extensive assignment and effective band parameters of the vr and vs fundamentals. Our forthcoming paper (14) will show the assignment of the v2 + v4 and v3 + v6 combination bands and discuss the observed perturbations in the VI, ~6, and various combination bands. II. ASSIGNMENT

A. Obserzqerl Spectrum

and Approaches

for Assignment

The high-resolution spectrum was measured at the University of Minnesota, as described in our preceding paper (II). Resolution was about 0.04 cm-’ in the range from 2720 to 2870 cm-l and about 0.07 cm-’ outside this range. The wavenumber accuracy was estimated to be 0.02 cm-’ in the above range and 0.03 cm-’ outside. More than 5000 peaks were observed in the whole range from 3400 to 2600 cm-‘. It was not easy to assign the observed spectrum, because there are several bands heavily overlapping and frequently influenced by either local or overall perturbations. For assigning the spectrum, a program system named SK (the third version) (IS) was used on a CDC 6600 computer at Century Research Center Corp., Tokyo. The LoomisWood diagrams and the ASSIGN diagrams described by Nakagawa and Overend (16) were helpful. A number of ASSIGN diagrams were plotted for the VI, ~5, and combination bands by the use of various sets of band parameters, and they were refined in the recycles while

VI AND

YS BANDS

OF H,CO

487

1 -

3

-

1

Ka=6(v2fv4)

Pushed

shift

dovn as

is

in

in

the large

whole 2.8

.35

ran e of J; _ cm-I at J-22.

of

1

Ka=7(Y2+.Y4)

Pushed

1

Ka=8(v2+Y4)

Pushed up in the whole range of J; possibly pushed up additionally by the Ka=10(v3+“4) level.

up

the

whole

range

.I

the assignment was extended. The ASSIGN diagrams (16) were powerful in making the assignment because they have the following advantages over the Loomis-Wood diagrams : (a) a simulated spectrum is used as a guideline; (b) the P, Q, and R branches are searched at one time; (c) the combination-difference principle, which is not affected by perturbations, is contained. Whenever a critical assignment was needed because of the presence of alternatives or possibilities of perturbation, the original spectrum was checked with the aid of the ASSIGN diagram. The observed lines thus assigned were marked on a Loomis-Wood diagram. Lines in different colors visualized the band structure and kept record of the lines assigned. Searly one-third of the observed peaks are assigned to single lines, another one-third are found to be blended, and the rest, mostly- being weak peaks, are left without definite assignments. B. Assignment of the VI Bad The rotational constants determined by our previous analysis of a medium-resolution spectrum (8) were used as the initial parameters to plot an ASSIGN diagram. Low J transitions (J’ s 1.5) for K,’ = 0 through 6 were assigned relatively easily on this ASSIGN diagram within 0.3 cm-l deviations from the prediction. The previous result (8), which was obtained by a combination of band-contour calculation and leastsquares titting, was confirmed in this procedure. Assignment of higher J and higher K lines, however, was puzzling because of the

NAKAGAWA,

488 'TableII.

0 1 2

3 4 5 6 7 8 9 10 11 *2 13 14 15 16 17 18 19

20 Pi 22 23 24 25 26 2, 28 29

1 2 3 4

5 6 7 8 9 1s 11

12 13 14 15 16 17 18 19 ED 21 22 23 24 25 26 2,

Observed

2 1 0

l l

2777.62

+ -

2775.22

l

l

2787.73 2119.84 2792.35 2794.86 2797.39 2799.98 2802.40 2804.91 28Q7.36 2809.05 2.312.32 2814.73 281,.22 2019.53 ze.21.99 2824.38 2826.70 2829.02 2031.29 2833.56 2835.74 2837.97 2840.08 2842.28 2844.45 2.846.51

~6, vz +

10

4

2789.76 -3 4 2142.14 -2 4 2794.55 -4 r: 6 2796.92 -3 Y 6 2799.29 3 * 8 2001.70 *8r13.98 -1 6 -2 , 2606.27 28OR.58 2X6 -1 6 2610.81 14 2813.07 -3 x 6 2815.24 14 2817.47 -1 * 6 2819.63 -1 x 6 2821.80 -2 1:4 2623.96 1x5 2826.15 1.7 2628.70 2830.46 3 4 3 4 2832.61 2834.7, 5X6 2836.86 1 4 5x5 2839.04 2841.16 4*9 3 2043.34 2845.3, -0 5 2847.53 4.+

and Their

2765.58

x

-i -1

3 6 4

4 5

1

-1

2763.20 -1 27bJ.P4 -1 -7 2758.47 0 2756.15 0 2753.82 2751.47 -2 -* x 274q.15 2146.85 2,44.50 27'+2.18 2739.90 2,37.56 2735.20 2772.88 2733.55 2778.23 2725.90 2723.57 2721.18 2718.81 2716.46 2714.10 2711.79

v1

a Band of H2C0.

6

5 5 5 5

6 6

7777.h?

2821.62 2824.17 28~6.10

Y 5

I

4

TVP.90

-2

5

277P.56

-1

?

2760.73

5

1

0 x fi

2765.87 P76'.52

-1

2817.01 2810,'6

-2

?775.?9

2787.04 -1 27P9.'S -2 27Q1.b, 2794.12 -c 27qG.32 2701.61 EBPn.q7 28'17.28 26nc.W 2.907.P, 2.810.lR 2812.45 8 2814.'7

16 16

2161.18

P75A.81 0 6 7756.4, 1 I 7754.12 0x 9 2751.78 i 6 2749.4' 3 6 7747.14 7X8 2744.90 7 5 2747.57 20 x 7 774".34 31 * 5 2738.24 56 Y 5 P7T6.46 114 x 6 7731.76 -121 = 273?.12 -53 x c 2728.P5 -22 4 2725.01 -9 * t 2'23,49 -5 3 2721.10 -0 x 4 2711.81 -0 4 2716.48 3x7 7714.10 3Y4

47 73 76 55

110 -if9 -Q8 -"F -10 -6 t -7 -F -‘

-0 4 OX6

I

0x5

e

l

7

1X6 i 6 2X8 1x8 4x7 -a l 7 1=7

5 4 15 3 4

6 7 5

x

5

3 5 5*4 4 4 x5 3 4 3 5 7x5 6 4 4.4 15 16

of subbands

v4,and ~3 +

Deviations.

5 Y 0 -1 Y 5 1

2772.77 2770.37 2747.98

2777.31 2774.81 2772.30 2769.82 2767.31 2764.83 2762.34 2759.86 2757.41 2754.91 2752.46 2750.05 2747.60 2745.14 2742.74 2749.34 2737.93 2735.56 2733.16 2730.80 2775.42 Zi26.07 ZIP,.75 2721.39 2717.02 2716.78 2714.L3

-.' 1 I -2 l l -2 6 -2 * 7 15 -0 Y. 6 15 4 l 7 * 7 3*, 4 l 7 1.8 8 l R -P 1 6 5.7 8'8 6'9 7x5 7 6 9 5 6Y5 10 5 5'7 12 x 4 17 l 6 14 l 5

overlap of a large number the US, v2 +

Transitions

27no. E784.93 2787.35

YAMADA AND KUCHITSU

0-r

27S4.22 2796.47 2798.94 2EPl.7Q 28"3.8* 28Ob.77 EBF8.70 2.911.17 2813.54 2816.ll 2818.41 ZG'O.qb 2823.4? 282~.95 2828.57 2831.37 2.334.25 ZB'R.5:

2767.31 7764.93 276P.53 2760.14 2757.77 7755.39 275'.01 7750.65 2748.31 2745.99 2743.64 2741.41 2779.17 2737.01 2774.85 P732.R4 2731.23 773C.86

2'6 7 , 9-* 13 18 21 26 31 = 37 Y 46 5, 69 Y 85 l 108 l 132 l 180 9 241) * 450 *

t 5 5 x 6 6 6 4 4 7 6 + 4 3 3

;

x 4

which

belong not only to this band

but also to

v6 bands. Irregular shifts caused by accidentalpertur-

the assignment even more difficult. In the firststage, the c-type Coriolis interactions between

bations made

be a major

source of perturbation

effective rotational constants

in these fundamental

v1 and ~6 were expected to

bands

(8). By

the use of the

(8), the vibrational levels of v1 and vg were predicted to

Table

Il.

(Continued)

Observed

P 3

?749.1?

4

2791.57

5 b

1794.06 2796.53

-2 -2 z*+ 3x6

7 ,

2799.06 ?401.59 7304.11 29116.63 2R00.21

9 13 16 I6 71

7811.77

?3

5

2814.35 ?.916.95 21119.51 ZRZP.lQ 2824.68 2b27.lh 2b29.71 2832.22 2834.77 2837.73 21139.67 2842.07 2s‘acr.*5

25 29

6 -

4

10 I1

I? 11 :C 15 16 17 19 19 2Q 21 22 23 2r 2: 26 27 23 29 31

5 6

x * l

l

5 7 6 5 +

30 S 6 311 x 7 31 l 8 23 I 6 73 ’ 0 21 ’ + 24 l 6 ?I 7 17 x 6 17 4 8.6

1 ‘

t 6 7 8 9 10 11 12 13 Iti 15 16 I7 19 14 2c 21 Z? 23 2* 25 Zh 27 28

2798.74 2793.16 2795.55 2797.97 28311.~9 2802.79 zoo5.21 2807.60 2810.04 2812.46 2814.nb 2817.31 2819.7Q ?SP2.‘1 2824.69 2tl27.16 2829.7i 21132.17 283k.55 2Hi7.15 2839.67 2rJU9.16 29u4.77 Zil”7.15

-5 -6 -9 -10 -12 -15 -lb -21 -?2 -16 -32 -34 -44 ‘k.3 -48 -54 -54 -66 -77 -47 -96 -119 -ill -115

5 7 6 7 * 7 x 7 X 8 l

l

I( 7 * b x 7 7 x 7 6 x 8 w 6 I( 8 l 8 I: q 4 X b Y 5 I 6 3

Transitons

and

2774.56 2777.13 2769.67 2761.22 2?64.bl 2762.34 2759. 86 2757.41 2754.91 2752.46 2749.98 2747.49 2?45.04 2742.49 2739.95 2777.45 2714.91

Band

of

H2C0.

I

I -22

P8F9.Q9 Ebl2.37 2814.73 2.317. ?2 281”.57 2821.93 2824.29

27kL.17 2741.67 2759.17 2736.72 2734.21 2731.71 2729.22 2726.76 2774.2b 2721.eo 2719.36 2717.Ql 2714.51 27iz.os 2739.62 2757.21 2704.76

PEZb. b7 282:s. 42 ZB?l. 37 Eb??. 7” 20’6. OC 2879.41 2.34r.77 Pbk’. Q7 Pbk5.37 PBV. 68 PW9.99 28~7.x.

2771.35 ?7h3.0b

-1 -r

2766.41 2763.99 7761.51 2756.59 2754.12 2751.60 7749.08 2746.59 27’.4.07 2741.51

-7 -b -8 -11 -ii -13 -19 -24 -26 -3i -37

2773.99 2776.46 2733.91 2731.32 7778.75 27Pb.ib P723.57 2721.!‘5 2718.61

-41 -45 -51 -5% -66 -72 -8Q -81 -93

2713.28 2710.72 2,08.011

u1

Deviations.

I

2732.43 2729.93 2727.4* P7?4.9b ?722.5* 2723.00 2717.54

i759.04

Their

-106 -112 -132

l

I

x a

I

x x

I I I I I I I

l

-4;

-41 -43 -53 -59 -6,

Y 8 x E E 5

x

b 5 4 4

x

c.

-6;

5 4

-711

I.

-7i -63 -70 -76 -75 -7l -77

I: ; l = + X b x 4 l + Y 7

5 *

Y 6 Y 9 x 7

l

-28 -31 -36

7 8 7 5 6

4 Y 6 Y 5 b 5 4 x 3 x 4 l + X 3 x 3 x 2

I

I I I I 2828.17 20r0.~’ PBZC. 47 28~5.72 2827.69 2WQ.Q~ Pm;;46 *w+4.77

-72

‘

-

-7‘7

.

,

-‘P -79 -55 -s>

x 5 ? 4 -

x t

-91 -ht

+ l h

I

2775.94 772*.r1 2720.b5 2710.33

-31 -t9 -39 -b1

x x

* 2 5

2717.3R 771”.89

-r7 -51

. x

t 7

l

cross each other around

J 2 21,

VI, K* = 2’++ vg, Ku = 111,

J g 26,

VI, K, = 3=+-+ v5,

J s 26,

v,, A-, = 4’ c-f vg, IL-,,= 3”.

K,

=

2*,

and

‘I’ht: (‘oriolis coupling

constant

115’ was estimated

to be 0.1387 b!. O~;L et al. (17) from ;L

490

NAKAGAWA,

Table

II.

(Continued)

K*s

4

“R J’

r kC

2792.57 2794.47 2796.92 2799.29 2801.7O

-4 -6 -3 -8 -IO

IO it

2804.11 2896.54

I2 I3 14 I5 lb 17 18 19 20 21 22 23 24 25 26 27 2R 29

2809.96 2411.34 2813.75 2816.15 2810.56 2820.96 2.323.~5 2825.7R 2820.19 2930.57 2832.97 2835.26 2(137.4?

u’=

o-c

6

PR 6 .I’

ii’=

LEVEL

l 110

k 5 6 7 r) 9

Observed

RQANPJL(

ORB (CM-I)

9’ IO 11 it 13 14 is

16 17 I8 19 29

4C

X * X Y ’

5 6 6 6 ”

2767.82 2765.35 2762.9I 276’1.46 7759.01 2755.54

-10 -9

*

6 6

2753.07 2751.6L1

-10 -12

-9 -13 -15 -17 -19 -22 -26 -27 -71 -37 -43 -60 -92

X 6 6 * 7 * 6 5 X 6 5 5 * I ’ 7 X 5 k X 3

2748.16 2745.67 2741.20 2740.74 2738.24 2715.75 2733.27 2730.76 2728.30 2725.73 2723.17 2770 * 60 2717.77

-12 -15

KS=

LEVEL RSANC” 0-c

'130

‘J

QP I

”

0 P 2 -2 -1 -6 -12 -a -10 -Ii -16 -10 -21 -?Y

X5 X 5

calculation.

”

-I -3 -4 -4 -5 -8

6

and

LEVEL

o-c *lOI

03s (CM-I,

‘)‘)T (CY-1) 2759.74 2757.29 27511.91 2752.46 2749. ¶a 2747.49 2795. Ok 27k2.57 2743.08 2737.hI 2735.09 2732.60 2730.12 2727.60 2775.07 2722.54

5

I

Deviations.

LF(IEL

nF. 5 fmp (CM-I)

“I K’=

RRANCH +I.ia’C

”

Band 5

00 I

of

H2C0.

LEVEL 5

ms (CY-II

BRbNCH o-c ‘IO0

”

4 4 5 5 6 5

2793.39 2795.48 2797.91 2800.34

*

6 -

2w2.79 2.385. Z!

4 :

X7 XB

2751.78 7749.3)

3x 7x3

i + X7

x

X 5 l 5 4 X 4 * 5 x 3 = 3 l + l t

2746.89 2744.50 2742.01 2739.52 2737.04 2734.54 2732.@6 2729.58 2727.00

4x4 11 l

-16 -21 -24 -25 -29 -28 -38 -46 -56 -90

PIC7.60 2810.04 2812.46 2814.86 zl117.22 2819.67

7 b

-16

5 5 5

o-c

”

,(‘=

7 6

I

7 5 7 7 .3 t 7 4 4 3 4 5 3 2 5

6 5 7

l

8

X7

7’8 7’R -7 X 7 -h X 8 -3 . l -6 -7 -11 -I7 -17 -+4 --17

4 X 7 X 6 X 5 5 x 7 k

7767.99 2761.51 ?759.09 275K.59 2754.17

hl: *ino

”

97

-5

.

27qh.J? 2798.62 PBOP. 86 PBO3.16 2805.ki EW7.56 28519.85

-10 -19 -‘4 -43 -57 -RI -9* -1lC -173 -IF,8 -196 -?*P -Fh -7P3

rYr (CY-1

J

279?.

2EiI.98 2814.17 2816.19 28I8.29 Ze.?O.kO 28T2.42 2874.52

2x0 X 7 I’+ -6 8 7 -3 t _

I

+

7 l + l 7 X 5 5 l 8 . 7 k X 6 l + l 6 X 4 3 3 l

b

2 6 -2 X 6 -k X 5 -5 6 -8 6 -9 4 -12 K -17 k -17 4 -20 4 -30 l 6 -25 X 4 -29 X 6 -36 3

x

7

LE KL 7

SRANCH

o-c

“a-

0

(CY-11

*IDO

2755.25 2752.74 2758.26 7747.66 2745.08 27kt.k’) 2739.40 2737.26 2734.62 2731.93 2729.25 2726.47 2723.75 2720.99 27IR.23

2X5 -4 X -7 l -21 X -3k X -47 X -59 l -I7 -94 l -117 -137 l -168 X -192 X -220 -247 l

+ 1) - K(K f

6

c

4

term in a symmetric-top

z C[d[J(J

6

8

nn

7

I

-I

2724.61 2722.11 2710.59 2717-I? 2714.62 2712.05 2799.62 2707.10 7704.56 K’.

7

I1P

‘100 -3 X -4 X 7 l 2’7 -I * -4 l -4 * -5 = -a -9 -14 -I7 -I8 x -2k -29 -35

-1 -7 -? 5’1

2U21.99 2824.38 2826.80 282Q. IO 2821.57 7833.94 28?6.30 28’8.71 2041.w 2843.45

YRANC”

The interaction

wl.FicG Ed.f(J, Kf)

KUCHITSU

Their

K’m

LEVEL 6

AND

BRANCH

I

“RS

normal coordinate

4 C

‘I

(CY-1,

2793.74 2796.15 2791.57 2890.97 2803.13 2805.74 2808.0~ 2810.43 20I2.87 2615.%k 2817.61 2819.96 2822.31 2824.68 2826.99

Transitions

20

6.

i

YAMADA

I

6 6 7 5 5 7 k + 4 + ? 5 k -

approximation

1)-J+

is then estimated to be 3.37 cm-‘, 4.15 cm”, and 4.13 cm-‘, respectively, at the above crossing points. If this is the case, the ~1 and y5 levels should be shifted by a few wavenumbers around the crossing points. This prediction, however, was found to be in conflict with the observation. Our conclusion at the moment is that the energy shifts due to this c-type Coriolis interaction are undetectably small (SO.03 cm-l). Nevertheless, the ~1 band is found to be affected by many other perturbations. In particular, the K, = Id levels are anomalously pushed up for .T = 16-19 and then pushed down for J = 20-23. This perturbation is attributed to the L-type Coriolis interaction with the K, = 2” levels of the vI + vg band; the observation of the plla branch of va + Q has definitely confirmed this interpretation. The effect of the Coriolis interaction with ~3 + vg is also observed in the li’, = 2”, 2”, 3”, and 3” levels of ~1, as

~1 AND

Table

I?=

BRANCH

8

ORS

12 13 14

Pi316.48 2818.96 2821.45

19 PO 21 22 73

8

K’=

9

“1

Deviations. LCVE

QR 0

39 41 56

27%. 66 2736.30 2713.97 2731.55 2729.22

2811.52 2.¶14*02

76

7726.

2724.43

3 I 4

l

65 76 91 96 tit

X 3 2 3 2 ‘ 5

I(‘=

L

Band

9

R’=PVCH

of

ti?CO.

LFVEL

nP 9

BRANTH

113

=

130

E7W.47 2798.94

2891.39 zao3.34 28Oh. 27 28P.8.7” 2811.2~ EBI?. 63 2.316.19 2818.0= 2821.17 2823.65 282h.iE 28T8.59 2a31.02

5

2

;i

25

a.

Their

SRANCH

2745.80 t703.43 2741.05

eear.11 2806.63

ia

i7

LEVEL

and

‘190

2799.20 2801.70

2809.09

8

1P

e79FJ.72

15 16

Transitions

401

01: HzCO

‘J I

0-S

ICY-II 10 ii

K’=

LEVEL

R

PP

J’

Observed

(Continued)

II.

vj BANDS

Observed

transitions

and

to

then

the

are

classified

branches;

they

according

are

listed

to

in

165 180 20*

2719*3h 7717.01 7714.71

the

the

upper-state

rows

of

K,

X b * +

l

levels

the

upper-state

and

the

first, J

values b.

Branch

name

component c.

Observed

in

(c”

the or

ordinary

notation

shoxs

AK,,

CJ,

h,“,

K-type

doubling

d”).

wavenumbers

(cm-l).

The

mark

(I)

means

that

the

K-type

doublet

1s

not

resolved. d.

Observed

e.

Uncertainty shouldered

f.

Intensity degradation

minus

calculated

marks.

wavenumbers

Blank:

reliable,

in X:

units

of

blended,

0.01 and

cm

-1

*:heavily

blended

or

line. marks. towards

Digits the

(l-9): high

peak and

low

heights

(qualitative),

wavenumber

sides,

+ and

-:

sbaulder

or

respectively.

summarized in Table I. This effect is compatible with the positions of the perturbing us i- v6 levels, which are predicted or actually observed in the low-wavenumber part of the present spectrum. Other remarkable shifts are observed in the K,, = 7 levels of vl; these levels are pushed down more and more with increases in J, and the shift is as large as 2.8 cm-’ at J = 22. This anomaly is interpreted in terms of the b-t\pe Coriolis interaction with the Ka = 6 levels of the vz + ~4 band. The perturbing levels of V~+ V, are also located by the observation of the rQ5, rRRg,nQ7, and pP7 branches, which are enhanced b>~ the intensity borrowing from the v1 band. The k; = 8 levels of vl are pushed up with increases in J by the Coriolis coupling with the K,, = 7 (v” + v,) levels. The v1 band is also perturbed at K,’ = il-”and 1” by the ~2 + VI levels as a result of accidental degeneracjy with the K,,, = 1” and 1” levels of vQ+ vI. The perturbations mentioned above will be described in more detail in Ref. (14). The use of the ASSIGN diagrams and the energy level prediction of combination bands provided the key-s to the detailed assignment of the v1 band. The ~1 band transitions finally assigned are listed in Table II; they are arranged according to the upper-state quantum numbers K,,’ and J’ in order to show the consistency of the assignment and the perturbation effect in the upper state. A part of the Loomis-Wood diagram (16) is shown in Fig. 2; only the vl band transitions are marked in this figure for the sake of simplicity. The Q branch (0 marks) clearly splits into the K structures. The qQ4, qQ5, and *Qa branches degrade towards the low wavenumber, and the *Q7 branch clearly splits into the J structures aligning in the same direction. The “Qg and $& branches, on the contrar!-, degrade to the high-wavr-

492

NAKAGAWA,

YAMADA

AND

KUCHITSU

1.0cm-t

PIG. 2. Loomis-Wood diagram (16) of H*CO in the range from 2800 to 2720 cm-‘. Only the assignments of the Yeband transitions are marked : marks a, 0, and 0 stand for the R-, Q-, and P-branch transitions, respectively.

number side. Each *QK branch is accompanied by ~PK (0 marks) and ARK (A marks) branches. The pattern of the K-type doubling in the P and R branches can be seen for low K. The “RR branches with various K values start nearly at the same wavenumbers and overlap one another. C. Assignment of the v5 Band

The initial basis for assigning the high-resolution spectrum of us was, again, the rotational constants obtained previously from a medium-resolution spectrum (8). Low J transitions for K,’ = 0, 2, 4, and 6 were located easily on the ASSIGN diagram where the wavenumber deviations were found to be less than 0.3 cm-‘. The assignment of the K,’ = 1, 3, and 5 subbands was more difficult, partly because of their smaller spin weights; namely 1: 3 for K, = odd: even in the v5 state and for K, = even: odd in the vl and the ground states. In particular, the K,,’ = 3 levels caused much trouble, because they- are perturbed at J 2 8.

40.1

The assignment of v5 was extended to higher J and higher K levels in parallel with the progress in the assignment of y1 and combination bands. In an early stage, our ASSIGN diagram showed slight systematic separations of the AK,{ = + 1 (rR, ‘Q, and ‘P) transitions from the AK, = - 1 (PR, “Q, and J’P) transitions going up to common upper levels.2 This suggested three possibilities : erroneous assignments, calibration errors, and errors in the ground-state rotational constants determined by microwave spectroscopy (1). The separations were independent of J but increased rapidly with K,, : namely 0.07, 0.22, and 0.65 cm-* for K,’ = 1, 6, and 8, respectively. This observation favored the presence of an error in the ground-state .‘I constant. Afterwards, Chu e/ al. measured new microwave transitions with AK,, = 52 and revised the rotational and centrifugal distortion constants for the ground state (4). On the ASSIGN diagrams based on these revised constants, such inconsistent separations of AK, = + 1 and - 1 transitions disappeared almost completely, except for the K,,’ = 7 and 8 levels, (LO.3 and 0.07 cm-‘, respectively. The NK constant obtained bj- Chu et al., 2.89 X lo-” cm-‘. is too small to explain the remaining discrepancy. This suggests that the ground-state centrifugal distortion constants can be improved by an analysis of the infrared spectrum. The perturbations observed or expected in the ~5 band are summarized in Table III. zThese kinds of separations were not detected in our previous work (68, and - 1 suhhands were not resolved simultaneousl>~ for high K, values.

II) because

the AK” = +

1

NAKAGAWA,

494 ‘Table

iv.

I?:

Observed

J'

r

0 DR

in

Transitions K'.:

LEVEL BSAYSH O-C '100

04s (CM-I)

Y.4MADA

0 C

DO

?I I

Their

and

IC

09s (CM-i)

Deviations.

LEVEL

K'=

"

I

1 EBbZ.hb e81r5.26 28117.93 285P.6, 2853.4'3 2856.20 2858.95 2861.74 2864.49 2867.19 2869.9,

9 9 ID ii 12 13 I* 15 16 I, 18 19 20 21 22 23 24 25

2872.*R 2875.08 2877.55 esso.o* 2882.43 2884.Ri 2807.11 2889.36 2891.61 2893.71 2895.92 2898.0,

26 2, 25 29 30 31 32 31 34 35

29'30.14 2912.24 2904.71 2906.72 2908.42 2910.31) 2912.41 2914.45 2916.41 2918.32 K'=

I

RP J'

1 ? 3 + 5 6 I 8 0 10 11

ii

13 14 15 16 17 1'1 19 20 El 22 23 El 25 26 2,

n*, 2 -0

2840.98

-I

x

4 5 6 5 5

II -2 OX6 -I 5 -B x 5 0 6 -1 5 0x6 -1 4 i.T(b -4 x 5 -1 x 6 -2 1 7 g 4 -II 4 -2 3 13 -2 4 -3 * l -1 9 5 -5 -4 -3 -7

r x I

3 5 5 3

ix2 -5 .

+

-I 4-5 2x4 -2 Y D nr

-I x -1 2X8 1 3X6 i 9 -2

2835.06 2834.89 29'4.65 283'1.28 2833.82 2833.22 2832.51 2831.64 7830.61 2929.53 2829.19 2826.73 2825.09 2823.2I 282i.22 2819.05 2814.74 2Bilt.28 2811.70 2809.03 2805.27 2803.44 2801.59 2797.76 2794.86

0 i -3 x -0 x 15 -2 -1 x -1 x -0 x -0 -i -0 x -1 l -3 -2 x 2X6 21, -4 . -2 x

2791.91 2789.06

CF"FL

il

WAVCH

PRr

1-r ill')

(W-1)

0 2 3 4 5 6 ,

u5 Bard

C :

DP

YRANCH o-c *lo"

AND KUCHITSU

6 5 6 6 6 8

5 5 8 9 5 6 5 6 5 5 6 7 k 5

4

2

HZCO/ K'=

1

PP "

I

D OC

LEVEL BRANCH o-c

ORS ICH-II

"

I

.

5

l IO0

c.

2837.60

-1

283n.E7 2828.31 2876.22 2824.17 28~2.i!! 2870.1B 2819.29 PBlF.36 2814.49 2812.67 28ifl.74 2888.84 28C6.89 28P4.91 28n2.56 280O.IZ 2790.68 27Yh.53 P794.34 27nF.07 2789.81 2737.48 2785.iT 2787.50 278C.F 2777.94 2775.5; 2773.11 277C.66 276~3.27 2765.76 2763.20 27FO.76 27~8.24

7 7 -7 Y 7 1 r -I X6 -3 x 7 (1 5 7x6 -2 5 -1 =, -1 7 -f 6 -0 : -1 x -ll x 7 -4 x 7 -0 l + -3 x 7 -1 x F -0 x s -2 x 5 -1 x 8 -7 7 -7 x 6 ix6 -1 x 9 -1 6 -1 x 5 -1 x 5 0 4 4-5 5.5 -1 6 F

af

2853.70 2855.98 2358.12 7860*20 2862.21 2864.18 2965.99 7067.77 2849.64 21171.31 787?.(J6 25,*.73 2876.49

-1

2x3

-1

4

-1 x 5 -1 4 3-7 -2 l 7 -6

* 4x4

x

-3

6 4

oxlr -3 l 0 -0 -3 I

29r0.21 ?979.93 2.581.76 2883.56 PBBF.37 7987.16 28OY.0, 2891.01 2892.94 7994.65 2996.85 2898.78 EYnP.77 2917.6@

*x4 2 0 -4 x -4 * -0 -1 -3 2'7 -1 I -14

5 4 3 4 3 6 2 3 2 3 3 1

* 6 4 7

3

LFVEL 99AlJSH

K'=

I D

"Q

2D

K'Z

LEVEL

I D

PP

BRANCH

?'

l_F\,FL WsWH

'('= i

C

Pr) oc

LEVEL SRANCH

"FF 1CY-1) 2846.46 28k3.n(l 2841.16 2838.41 2835.61 ZR3Z.SO

-2 4 ia+ -1 1 8 -1 Y 4 2 '5

2'124.YE 2826.99 2824.13 2821.1, 2818.79 2815.*3 2812.67 2809.76 2807.02 2804.31 2801.59 279R.9k 2796.37 2793.74 2791.13 2718.5, 2786.04 2783.51 2TOO.9, 2778.lr7 2,,5,87

i 4 -2 Y 5 T*6 -2 l 6 -1 l 6 -1 X 6 3Y7 -4 4 -1 4 1x5 -2 l I -1 x 5 -0 + 7 1'5 -1 '( 4 -1 x 4 IV6 0x5 o-9 2 l 9 -6 x 4

2815.29 2818.08 2817.76 2817.22 2416.74 2816;15 2?315.r3 2814.62 2813.68 2812.73 2811.63 2810.49 2809.21 28P7.79 2806.35 2814.B.2 EBO3.16 2801.39 2799.62 2797.76 2795.79 2793.78 2791.67

-5 l -0 3x5 -7 l -2 l

6 2 8 6

1.6 IX6 1x5 -4 l ix4 0 4X6 k +-1 2*+ 3 ix5 -4 + -2 -0 * -1 -1 l -7 l

l

4

4 4 7 3 6 3 + 5

2813.64 2111.04 2808.33 28C=.53 2007.51 27w.4, 2796.22 2792.83 2789.24 2715.44 2781.46 2777.23 2772.77 2,FR.O' 2763.C?

2551.4#4 2851.60 2851.84 2852.13 7952.53 2115?.06 2853.7P 2854.43 285E.33 2856.35 2857.49 285.3.8, 7560.29 PSb*.Yt 286'.62 2865.57 2567.62 2869.8, 2871.99 2874.79 2e76.6,

0x4 1 r -1 -3 * -1 -0 Y -1 x 0 i -2 -2 -2 -3

-1; -9

3 5 3 6 4 5 4 k 4 5 5 4 ‘

; X

6

Small perturbation shifts are observed in the K, = 2d levels at J = 16 and 17; they are caused by the Fermi resonance with the accidentally degenerate K, = 4d levels of the va + ~6 band. The K, = 3d (Q,) levels are also perturbed by the K, = lc levels of the L++ y4 band through a third-order u-type Coriolis interaction. These levels cross each

VI AND

Table

IV. K'=

I

P" J'

Observed

(Continued) C

LEVEL

7r

BR&YW

0.W (CY-1)

1 E 3 4 5 6 I r! 9 10 ii

2818.80 2819.05 21319.36 2819.63 2819.96 2820.44 2820.91 2821.17 2821.49 28*1.80

12 13 14

2.32i.49 2827.10 2822.IO

15 16 I7 IA 14 20 21 22 23 24 25

2.321.93 2821.62 2021.17 2820.47 2819.63 2818.65 2017.47 2816.15 2814.49 2812.77 2810.74

n-c '100

K'=

Transitions

I C

Pi= 20 u

I

-3 x 4 0*5 4'6 -2 l 8 -6 X 5 014 2x5 IT6 -1 x 4 2'6 1.7 1'7 2'7 -2 = -4 Y -5 l -13 -16 * -15 '( -13 x -4 l -8 l -3 x 1'6

6 4 6 4 (I 5 4 6 5 4

YE,BANDS

and

u

I

RP r)W(CM-11

D *r

LEVEL

WC -190

"

2859.21 2856.64 2853.*0 2850.97 2847.8.9 2844.77 2841.61 2838.34

-19 3 0 7 I*3 1x4 3vfl LK6 14 -3 l +

P835.lh 2831.71 2828.30 2824.84 2821.33 2817.76 2814,PI 2810.49 2806.89 2803.37 2799.77 2796.15 2792.69 2789.30 2785.04 2787.54

-1 -* -0 -0 -1 -5 -3 -19 -?3 -*3 -12 -40 -41 -42 -55 -59

x 6 * + Y 7 y 4 'I 6 '( 5 * l x 6 l 7 l + 3 x 5 3 l + * 4 l *

K'=

LCVEL

2

Rn

9WNCH u

I

of

H,CO. i

D

LE'wFL

10

BRDMCH

net ICY-I)

o-c 'LOO

Ll I

2871.99 2874.10 2876.?4 287e.39 288n.46 2832.32 28P4.12 28*~.84 2887.57 2.3e9.07

1 4 -1 l + -7 l l -4 4 4 4 -1 = + -1 7 -7 x 4 1x4 -1 X 6

7467.40 ?,67.62 2867.90 2868.30 7868.77 2969.31 2969.R7 207*.59 2871.3i 2.372.15

-1 ‘t -2 4 -4 4 -I 4 14 2 5 -2 * 6 i 5 -4 4 -4 x 5

2792.79 2791.24 2749.76

-0 -3 -2

2.39C.S~ ZP,91.96 2893.32

-2 -4 -7

-5 -2 -2

P7a8.28 27116.86 27.,5,44 2733.98 2782.48 2781.08 2779.58 2778.11 2776.53 2774.92 2773.23

PR I

u5 Band

1'3 -3 l 7 -0 * 6 0x5 lb*.4 -3 l 5 -4 x 5 8'7 _I . _ -0 x 4 -4 * 8

1

4 5 +

-5 x 4 -5 l 6 -6 c 7 -ii Y * -20 4 5 -16 = + -i.3 + 4 -13 2 -13 l + -8 2 -5 x 3

K'=ZD

R~hNSII

Deviations.

Q-C '1'10

m(CV-1)

2*?".6' 2W5.85 2896.97 28YB.T? 2899.17 29DC.20 2901.F 2Yp7.?2 PYp3.43 2904.5s 29OG.72 2906.68 2907.79 EY11R.78

K’S?

14 15 16 17 i.4 19 PO 21 22 23 24 25 26 27 2s

1‘

405

28t3.83 2811.52 2809.34 2807.22 7895.21 2803.16 2801.25 2799.47 2797.70 2796.01 2794.34

26 27

7

2D

RP

?d

J'

Their

K'.

LEVEL BRANCH o-c *loo

ms (CM-l)

OF H&O

n3r (CM-11

2813.75 28lb.15 2811.49 7820.81 2823.10 7825.38 2827.58 26'9.76 2831.83 2033.87 2.535.74 2437.57 2839; ii 2840.66 28k2.07 2E43.16 2844.14 2844.95 2845.50 2845.?0

LEVEL 3C

K'=

BRlNCH o-c

"

I

l LOO

-I

* PSb -0 x -I x -1 i -1 I*+ -2 -4 x -4 x -4 x -20 -21 l -21 x -35 ' -41 -42 l -46 -51 *

2 V

Pr, ?7

7 5 5

3 3 3 3 6 5 5 3 k + 3 3 2 -

PIT (W-1)

2801.59 PW1.59 ZLI"1.43 2801.3q 2801.2~ P&PI.?7 280@.¶6 2.300.59 28rt@.?Y 7799.88 2799.47 279Q.02 2798.30 7797.64 27Q6.97 2746.01 2795.04 2794.92 2792.96 2791.67 27YO.38 ?78R.71 2717.04 2785.17

x

? ? 4

2873.06 2674.09 2175.15

-7 Y -4 . -ii l -** x -?F. -7r! -26 -4' . _I,* -94 -El

5 7 + 5 4 4 2 + 7 3 ?

Zil76.26 2877.55 7978.68 28en.04 2881.43 2882.76 7834.76 T88E.84 7887.46 2889.07 PbYn.74

-9n -111 -IKP

LC"FL

x'=

”

?

PP I

m!P

(CY-1)

'100

-3 i 7-7 1st 7'7 1x5 -ri -1 x -2 Y -7 * -7 x -7 x -2 -70 -12 -'7 x -74 x -42 -45 1 -4r x -57 . -<9 K -91 -ii2 -L&C

4 + +

x x x x

5 F 4 6 l El l 4 4 x 4 l e 6 + +

' x 3 x ?

"POMCH

n-r

-7 -I -17 -** -22 -38 -42 -44 -48 -56 -63

* *

x * 1

7

5 7 5 6 h 7 5 4 4 6 4 4 R ? c, ?

7794.42 7791.96 2789.53 2787.01 7784.&l 2752.04 7779.48 2776.89 2774.77 7771.58 Z763.80 2765.96 2763.C3 2759.91 7756.85 2753.38 Z749.98 2746.24 2747.75 2738.24 7777.91 77?Q.34 2724.57

D 3:

LEVEL RR&NC"

q-c

IJ I

‘100 2 -0 3 -2 x -2 l 2 2 I4 -3 x 2 -L -2 x -3 -3 X -2 -29 -14 l -24 -30 = -37 * -42 * -47 x -50 *

7 7 7 8 7 4 5 6 5 4 6 c. 6 7 Is 7 4 c. 5 7 4

3 l

CI

other at J 2 9 to give the observed perturbation shifts of cit. 0.3 cm-‘, and several transitions of the ~2 + ~4 band are observed as a result of the intensity borrowing from the v6 band. Crossing of these levels is again expected around J = 24, but the assignment has not reached the crossing point. The & = 8 levels of ~6 are found to be pushed up b> more than 0.4 cm-’ for the whole range of J. In this high K region, the ~6 state can couple strongly with the vz + ~6, v2 + ~4, v3 + ~6, and vz + ul states through the Fermi or a-type Coriolis interaction : The u-type Coriolis interactions between the vz + vii

496

X4KAGBWA,

Table

K’.

2 r

287k.73 2877.35 2.380.15 2882.97 2806.01 211n9.14 2892.44 2095.92 2899.bO 2903.49 2907.57 2911.86 2916.40 2921.21 2926.25 2931.49 2936.97 2942.7* 29'18.57

K'=

LEVEL BRANW

DES ICY-I)

2.301.70 2.301.70

5 6

2001.70

ii I2 I3

1C I5

16 17 18 I9 20 21 22 23 2r

_: -5 -2 -2 -4 -7 -* -ii

St-

3 4

7 0 9 10

4x5 -I 2*+ 4 ‘( -0 -1 * -2 -i 4 -0 l 7 x

2 r

PQ J’

LEVEL

K’=

Transitions PC

in BRPINCM RQIC

RR

2 3 4 5 6 7 0 9 IO I1 12 I3 14 I5 lb I? I.4 19 20 PI 22 23 24

Observed

(Continued)

IV.

YAMADA

2801.70

2801.77 26Oi.R8 2802.03 2802.23 tSO2.50 2.302.86 2803.28 2803.76 2104.31 2104.91 2805.59 2806.27 2806.119 2807.56 2808.09 2808.58 2608.96 2009.24

O-C ‘I00

3 5 3 l

2 + + 2 3 . Y 4 X k . + * 4 3 II 5 x 4

K’:

? C DP

1,

I

01.3 1-5 -0

2866.91 2866.68 2866.36 ZBbS. 99 28b5.57 2865.13 21164.64 2.564.18 2863.73 2863.33 21163.01 2862.77 2862.62 2862.58 2162.70 2862.96 2863.33 2863.91 2962.64 2865.49 2866.52 2867.77 2869.17

l

n

-3 8 8 -1 1 + * 4 i 4 0 4 1x5 ix7 1.7 0 X6 -* X 5 -2 l 7 0x7 1'7 -5 x 7 -3 ' I) -ii K 6 -1' Y 6 -23 ‘( 6 -27 * 7

00s (C*cI

30

and K’Z

LEVEL

-e x 4 -I 5 -I 4 I 7 2 X6 3X6 2x7 2X7 0x7 OX6 IX6 I*+ -0 X 7 -2 x 4 -I X 7 -0 x 6 -C X 6 -3 4 -3 X 7 -II K 7 -17 4 -20 X 6 -25 5

”

19

26hP.W 2858.27 2W6.20 2854.33 28C2*~7 E85P.97 284". 37 2847.98 2846.84 2045.97 2e.45.13 2844.58 2844.28 204*.23 28'4.45 2844.95 2845.61

K’=

LEML BRANCH

3 PP

I

*loo

6 7 't 5

I, 4 5

-5

l

+

-0 -4 -1

l

+ 7 5

x x

Deviatlans.

us K’=

L’VEL RDAWH

Pw-

c x4 I 4 -5 x 6 0 3 0 l r, 1x4 7 4 -1 l l IX6 IX5 7x5 -1 7 -2 l + -7 * 4 -? 8 F, 2'3 -7 7

2889.88 28"7.'0 28Q4.61 2897.?3 2899.39 2981.51 29"3.51 29FE.72 2907.79 2909.75 2911.63 2913.41 2915.94 2916.49 2917.89

”

-D P

I

7 7 l

+

x 8 x

-66

2

LEML

2 2 E

L 2 3 -5 ._ 2 7 * + X4

C ?O

3 PQ

.l?r!

-60

of

2813.83 2816.3@ 2519.60 7821.33 2823.96 2826.55 Ee.29.35 2832.I7 283~.06 2838.11 ZV+I.PI 2844.45 25r7.77 2851.16 29W.63 2858.10 2861.74 2945.47 2861.10 2872.84 K’=

WA WH v-r

Band

Pp.

LFVEL 2:

(C"-11

-1 -0 * IX6 2 5x5 IX5 3X5 I 3 -I l 0x7

-11 -14 -21 -27

23 Pn

I I 274i.11 2704.71 2782.35 2750.111 2777.74 2775.55 2773.37 2771.35 2769.37 2767.54 P765.76 2762.iP 2762.53 2761.13 2759.74 2759.42 2157.21 27r5.95 7754.Yi 7753.82 ____

RUCHITSU

Their

BRANCH

O-C

I

AND

H2C0.

BRANCH

-2 x -I . 0x4 -0 X 3x4 -4 l 2X6 2-n -1 l 14 -I X 0.6 -0 X -2 -6 -8 i -I6 = -1.4 l -24 = -27

3 * 6 +

6 6 6 4 * l

E + 3

LEVEL 20

SRAWH

MS

n-c

(CY-II

'100

2!?82.63 7982.63 2082.5R 2B82.58 2Bll?.5(I 2882.76 2R42.18 2902.27 28.3F.72 2982.37 2MZ.43 2982.L;8 fWf.76 209?..¶9 Zl)B'.lO

II

2-r 58, 2=7 k.7 6-7 24 l -35 X -29 l -30 l -34 8 -40 l -42 l -45 l -59 v -70 x

I

r 4 7 7 4 2

5 3 * 7 l 5

and vz + VAand between va + IQ,and vs + v, become very large for high K (W z 1O.K cm-l), and, consequently the v:!+ vI and va + v6 levels come much closer to the vg level. Furthermore, the Fermi resonance terms between v5 and v:! + v6 (namely, the cubic constant k&2(2)$) and between v5 and ~3 + vc (nameI\- k&2(2)+) are rough]! expected to be as large as a few tens of wavenumbers. Thus the vg levels at high K,, (K, 2 8) can only be interpreted as a result of the heavy interaction among the above five vibrational states. In order to interpret the shifts of the K, = 8 levels and to assign higher K, levels of v6, such an analysis of five-state interaction should be necessary. The vs band transitions presently assigned are listed in Table IV according to the upper state K, and J values. Figure 3 illustrates a part of the Loomis-Wood diagram; the same part is shown in Fig. 2, but the Q, band transitions alone are marked in Fig. 3 for the sake of simplicit!,.

~=ble

(continued)

Iv.

K'.

3 D

Observed

K'=

LEVEL

Transitions

3 D

ar.d Their Km=

LEVEL

?

D-C *lOa

: 6 7

II 9 10 11 12 13 14 15 16 17 . ^

2865.75 2862.70 2860.12 2856.53 2054.07 2851.06 2a47.99 2844.77 2841.41 2837.97

-1 1 7.7 irJ l -34 Y -28 + -31 l -3, l -36 l -43 s -48 l

2 3 5 + 6 6 5

vS Band

y'=

LC"FL

rmfi W”

3 C

PR

70

5-7 I l 1'8 E*+ PO l -29 l -24 9 13 l 18 l -37 -40 -49 x -58 X -67

*

7 4 4 9 9 4 4

5 b 4

2774.91 2772.3') 2769.Bb 2767.4' 2765.02 2762.64 2759.64 2757.2I 2754.10 275P.M 2749.65 2747.14 2744.5@ 2741.06 27'9.17

2914.52 2917.17

2919.92 2922.73 2926.71 292R.78

1c

2931.97

20 21 22

2935.38 2936.90 2942.72 3

r

R" 2r J'

9

10 11

12 13 14 15 16 17

18 19 20 Pi

22 23 24 25

')flc (CW-1) 2882.b3 P892.5E 2802.47 2882.37 2882.27 28a2.05 2.581.91 2881.57 28.3i.ii [email protected] 2*10.1(1 2879.44 28?8.?0 2877.99 2877.14 2876.34 20r5.43 2874.60 2073.74 2877.98 2872.10 2.97l.hR 2071.11

K'.

LEVEL RP.4NC.Y 0-c '180

v

I

3 C

RP

ZD

nss (CY-11

LEVEL 9RPNC" D-C l100

" I

K'z

3

-

PP 4-l WC (CM-i,

K'.

Lr'JFL QF'LYCH 0-p 'l??

‘

+

-0

.

_

4*-

1 P b 4 7 7 5

-

2'4 914

4 4 4 4 3 t 4

2865.57 2863.14 28hO.74 2858.36 2855.9d 2853.70 2851.44 2849.2') 2847.15 2845.13 2843.23 2841.41 2839.7d 28vl.24

2'6 IX2 3 2 3 2 08 3 3 4'4 8 3 7x4 6 15 4x5 5Xb 6 x 3 1x3

7i

3 c

WJ 4C

IJ I

4-t 3=7 -0

LEVEL l3RPWH

OR? (CM-I)

7794.51 P7R4.44 2784.40 2784.40 2794.30 2784.30 2?84.3? 28'1.94 2113.4h te.is.an 281P.41

I

I 2097.17 2899.
19

K’C

of H2C0.

D-C u ri0o

U I

3

2784.51 27"4.++4 2704.40 2784.44 2794.51 2783.98 2783.98 2784.30 2704.30 2703.69 2713.59 2783.43 2783.26 2753.07

D 4”

Pr-

J’

Dcvlations.

hXC E 7x4 9x3

2X8 4 4 1'1-r -0 . l 4 :x6 a.+ 7 3 9 2 I.10 ’ 4 9x1

bX4 7-7 o-5 3x5

LEVEI SRLNCH D-C U '100

I

587 1-t i-3 4-5 -2. 9 1.9 449

P

5x4

The “03, “(j,, P&, p<&,and “Q7 branches are observed and resolved into their J structures. The “Pa branch splits into the K-t!pe doublets. The ~‘I-‘,branch also splits into the K-type doublets, and one of the components (having K,,’ = 3’1) shows a hJ.perbolic form characteristic of a perturbation around the level crossing. An anomalous gap can be seen in the “Q, branch, correspondin g to the perturbation in the “Pj branch. A superposition of the assignments in Fig. 2 and Fig. 3 demonstrates the complexity of the observed bands in this region. III. RESULTS ‘4.

.4ND DISCUSSIOS

Effective Parameters for the vl Bad

By the use of the assigned transitions. least-squares fittings were made to determine the effective rotational constants for Q and vs. A preliminar!. fitting to the vl band

498

NAKAGAWA,

'Table IV.

(Continued)

K'n 3 C PP 4n J'

OBr ICU-1,

YAMADA

Observed

LEYEL

K'=

RPPNCH

Transitions

4 D

RR

o-c " I l IO0

3C

nss (C'1-II

AND KUCHITSU

and

K'=

LEVEL

u

Ueviations.

4 D

PC) 71

BRPNC" o-c 'IDO

Their

I

l-m(CM-I)

v5 Band K'=4D

LFVFL

t_EYEL

RP VC

CPANCH

of H2C0.

SRANCI( 0-c '100

n-r " I '1Cll

u I

I

4 5

6 7 8 IO ii i2 13 14 15 16 I? I5

19 20 21 22 23 24 25

I 276C.93

1X6

2162.'+7

2

1759.99 2757.56 2755.11 2752.60 2750.26 2747.16 2745.46 2743.20 2740.87 2738.66 2736.46 2734.40 2732.43 2730.55

K'= 4 D PP 5c

J’

04s (CY-I)

zx: 4 5*6X6 7X6 b 11 l 6 8X3 C*6 4 5'6 4.4

7

3

4 5 2

3

LEVEL

K'.

RQPYCI(

o-c u

2912.10 2914.45 2916.82 2919.17 2921.52 2923.81 292b.14 29?3.37 2930.64 2932.80 E934.99 2937.12 2939.17 2941.18 7943.15 2944.93 2946.69 2948.32 2949.79 2951.24 4 D

PQ I

'100

2 4 2 6X6 3 6 2 5 7 7x5 10 lb X 17 17 PO Y 18 Y 2R

nRS (CM-I)

5D

5 1:

4 S 5 2 3 4 6 4 4 3 6 3

K'=

LEVEL

”

I

l 100

4 e 7 R 9 10 ii i2 13 14 15 lb I7

ia

19 20 21 22 23 24

2786.21 2786.57 2790.94 2793.33 2795.65 2797.97 2800.33 2602.79 2805.09 2807.50 2809.85 2012.?I 2814.62 2616.95 2619.36 2621.70 2824.13

3'5 1x4 1x4 4.x -1 -4 l 1'7 5'7 -I Y 5*4-7 4x5 9x5 6" II l R'I6 l

4 5 7

I I I I I I I I I I

6

6 6

I 2766.12 2766.04 2766.04 2?65.96 2765.87 2765.82 27h5.76

5X7 4X6 11 X II Y 9x6 11 = I3 X

4 D

PP c,r

BRANCH

o-c

I I I 2897.12 2b9h.97 2606.45 PW6.70 2896.58 26W.43 PR96.15 26~6.19 289b.?h 2.39s.92 2e.OF.b~ 2txq5.7q 28?C.7S

6 b + 5

@PV IC"_Il 27w.77 2752.77 2740.3r) 2747.39 2744.91 2742.42 2739.95 27?7.45 27'4.91 2777.43 2724.97 2727.44 2724.96 2722.44 27Pll.OD 2717.w 2714.99 2712.46 2709.95 27P7.47 27"4.c)h

c*tl 7.7 4*7 ZXh CXh 416 -9 4 10 + i" X 9++ 14 * I6 l '7 +

+ h c 7 _

2352.97 ZBR(1.51 2877.99 PR7'.46 2972.98 2670.40 2867.77 ZRh5.1? ij62.51 ?r)59.R? 2357.@7 2854.27 2551.44 2648.45 284G.37 2842.20 263O.ll4 2835.61 2932.17 2828.51

LFVFL

K'= 4 C

wer,ckl n-r 'IOF

LJ I

-2 h -I h 2 5 n 5 15 18 ZX7 15, -2 h -r) X b 1 Xb P 6 c 5 4 b IO Y 6 S'I? X 6 in x 5 IO X 't Ii X + IC 2

DR 3D "RS (CY-I)

-* *

6X' 5x4 I'b -I l b * 3 4=+ : I2 * 9 7'C I5 l I7 X I3 X 20 4 27 x

& = 2 (J = 2), K, = 6 (J = 6-12),

K, = 1” (J = l-16), K, = 3 (J = 3),

4 5 4 8 9

LEVFL

u I

-I X 6 2 t‘ 3 : 4 3 7 7 4 5x5 8 5 5 7 b 't 5x4 4x7

transitions left large deviations, which were systematic within each subband random with respect to I&. These deviations reflect local perturbations origins as discussed above. Therefore, by inspection of the energy-level and scheme of the y1 and other closely lying bands, the following levels of ~1 were being relatively free from perturbations : K, = 0 (J = O-20),

3 4 4 ?

SRANrH o-c -100

I I I I I I I I 2926.14 7928.48 2930.80 2933.08 2935.36 7937.77 2940.01 294t.37 2944.68 7947.06 2149.45 2951.90

5

2=+ 0x4 0x5

but nearly of various interaction selected as

K, = Id (J = l-lo),

K, = 4 (J = 4),

K, = 5 (J = S),

k’, = 7 (J = 7).

A least-squares analysis was applied to 117 transitions corresponding to these VI levels. Slightly blended transitions, which are denoted (X) in Table II, were given weights one-quarter of those for the unblended transitions.

Table

Iv.

K’=

4 RQ

J’

Ol~~er~ed

(iontinuedl

C 3C

K’Z

LEVEL RRBWII 0-r Cl10

OBS (CU-11

4

2897.63

l.++

2897.57 2R97.57 2897.4?

1-7 1’7 -2

4 RD

I,

5 6 7

1

I

7

I

111 ll 12 13

1‘7 4 * 3 + 1’7 5.6

*7

t4 15

21196.43 289R.19

1.6 ? r

h

PR60.20 2857.64

Lb 17

2895.85 2895.c.l

1 6

7 3

7855. 7852.53

15 19 70 2t 27

2045.11 *894.hT 2893.94 2593.17 2897.&7

7x7 $05 7x4 b 7x7

23

2891.74

2

l

*3

artd Their K’=

LEVEL

(1-c *loo

”

I

m’: , w-1

+

C 51

LrwL

K’Z

MAYCH r!-p rjls

1

I 2875.40 296,. 2865.32 2862.7,

u5

4 prl

Ll I

Band C 5C

91

3 1 B-1 2x5 4

ii

2849.99 2847.%9 2.3k4.95 PB%2.50 2840.08

*

8 6

’

s

l

11 x 7-3 9x* 8 *

25X,.69

4

I I I I I ,

x 4 x4 x 3

=

7

I I 28”9.9? ERi2.?7 2814.77 2R17.1F 2819.57

k

2821.9Q

4 6 4 r

H?CO.

LEVEL BRAKH

-2

? . C’7 6 l F..-i -T

t r(

l

6

l

,

”

I

x

5 5

2* 2*+ OX’ IX<

276F.RA 7761;. 63 2766.76 7766.71

I -2

of

cl-c *ioo

09s (CM-l)

7?6b.~.Y

I I 0

4 VP

3RbtYcH

UeviatlO,lS,

I I I

2897.17

l

C 3D

ORZ ICtl-1)

.7697.77 2097.19 ZR97.07 2896.95 2496.70

8 9

Transitions

2* 2

2766.67 27bb.60 2766.117 2766.41 2766.41 2?bb.?34 7756.79 7766.77 2766.16 2766.12 77bb.i? 7766.17 2766.12 Zlhb.17

-4 -3

x 4X6 3X’ 3-t 4 x 3=+ 3 * 6’7 8.7 78 58

+ 4 5 6

7 7

7 7

I(‘=

4 00

r 5”

LEVEL R94*JPv

I 5

I

6 7

I I

P

1 1” 11

l? 1’

14 1= lb 17

1e

19 21 ,2 73 -__-_

/

I

I

I I I I I I I 2720.8rl 2717.c4 2712,44 2710.20 270?.?F,

416 7 X6 ,=r

I(‘:

5 ?P

~-

LFVEL *

?Q?h. 34 2926.71 2929. CL 2931.40 2977.72 2916.04 29x*. 34 ?9kB .64 ?94.96 T9‘5.24 ?947.49 7949.79 2951.99 2954.21

BRA hCH .____

u’=

5D Pn

It,

LT”F

KS:

L

WA”,CH

-__-

I I

LEVEL b

5RANCP

7774.54 7712.06 7779.5ll 77~7.05 772k.57 172?,F3 P719.&9 7717.01 ??14.~1 7711.q7 2719.45 27116.93

I I I I I I

I

I I I 791F.38 2910.

E. pp

?Z

? ”

l

++

+

2791,w 7hY.3,

Six parameters for the ~1 state were determined in the analysis; the band origin (Q)> the rotational constants (2, 8, and c), and two centrifugal distortion constants (AJK and AK) in Watson’s reduced Hamiltonian (18) in the asis convention of Ir (s = h, y = c, and u”= a). Three centrifugal distortion constants (A,, JJ, and 6~) for v1 were fixed to the values of the corresponding ground-state constants determined b!, Chu et al. (J), because no high J transitions were introduced in the analysis to avoid the effect of local perturbations. The ground-state constants were fixed to the values obtained by Chu et al. The effective parameters for the y1 band thus obtained are listed in Table V. Three times the standard errors are shown in the parentheses. The standard deviation B for the 117 transitions fitted, 0.019 cm-l, is slightly- larger than the wavenumber precision in the present experiment, probably reflecting local perturbations. The wavenumber deviations are listed in Table II for all the assigned transitions of the ~1 band, including those not used in the least-squares analysis. The reliabilities of the observed wavenumbers are also marked in Table II. The deviations of the z+state energy levels were obtained by graphically averaging the deviations of the P, Q, and R branch transitions, as plotted schematicall>- in Fig. 4. The K,, = o&l levels

NAKAGAWA, YAMADA AND KUCHITSU

500 Table

IV.

(Continued)

Observed

LEVEL

K=5C

1(=5r R"

*r

RPANW n-c +I00

u

OBS (CY-1)

5 6

2912.19

-0

2912.10 2912.02 2Y11.97 2911,Rb 2911.73 2911.63 2911.51 2911.73 2911.20 29ll.01 2910.84 2910.59 2910.32 2910.06

-2 l -3 l 1-t -0 i -3 1 -0 . 2 -1 3 3 6 3x3 1'4 2'3

R

s 10 11 12 13 14 15

I

and

6C

fl0S (CM-11

Their K=

LEVEL

Pa

J

7

Transitions

6D PF' 9-

BRANCH o-c u li!_lo

I

5 _ t _ 2 II 3 4 3

-2 2 3 -3 2 -3 -3 2 -3 x5 -1 3 1 4 3 0 2 x b 6 Y 6 3 3 4 4 1 X6

27k8.96 *T&8.88 2748.81 2748.74 2749.65 2740.58 2748.50 2748.39 27Q0.31 2748.23 2748.09 2747.98 2747.86

2940.81 2943.1' 2945.57 29h7.81 2950.1" 2952.41 29C4.7" 29C6.96 29co.22

2e

2948.87

19 19 70 21 27 23

74

K’=

LEVEL

5

PP

7

"qr

J'

(CM-i, b 7

9 9 1C 11 12 13 14 15 lb 17 18 19 20 21 22 23 24 25 26 27 28

2717.91

2711.39 2708.91 2716.4, 2703.87 2701.36 2698.78 2696.77 2693.70 2691.17 2648.56 2685.96 2683.'(9 26?.0.78 2678.18 2675.55 2672.97 2670.74

K'=

BRANCH (I-C !J I

-3 -7 -? -5 -3

3 5 2 . + 3 3 2 4 Y 3 * +

-7 -9 -8 -10

3 3 2 7

-7 -4 -5

-11 -14 -12 -15

l l

6 C

RP

+1'10 -3 -7

6

PQ

~~ANCt!

D 50

ORS ICM-11

u

I

5

x

I

6

I

6

I

of H?CO. LEVEL BRANrH o-c '100

u

r

l

1

‘ +

*5 26 27

17

us Band K =

LFVFL

n-c l l??

ner (CM-11

2961.41 2963.64 2965.36 29hP.03 29'0.23 2972.35 2974.54 2976.62 2970.7, 29ar.77 2982.82 29P4.90 29R6.87

16

Deviations.

? + + 3

OBS (CM-1)

K'=

LEVEL

50

I)-c u I l 100

I

I I I I I I I I

I I I I I I I I

2996.87 2988.99

-21

K

-11

x 3

-I -5 -2 -5 -4 -4 -3 -7 -7

5 6

-5 -q --o -17 -1s -ti -16 -16

1 I

x

6 6 6 5 x 4 x I+

-6 -P -6 -9

5c

I I I I I I

F 4 4 4 6 5 6 x 6 4 4 Y 6 X 6 x

LFVEL

I I I I I I I I I *9?1.68

K'=

qFANCH

n-r ii"?

2¶?6.25 29P6.10 292h;i4 2926.91 29fC;.?l 2926.71 29?5.96 4? 29??.21 292E,Or) 2924.7' 2924.54 2924.14 2974.07 2925.74 292?.48 2923.1' 2972.75 2922.45 2922.I4 Z¶?1.b7

--c.

1,

-7

l

+

l

6 -

7 1 -7

" I

. .

x

4 Y 4 x 7 1

7 7 .

-

3 1

-13

6

w

0PC (C'r-ll

i92’;

I

-6

6 ^

CQ

SRANCH

-6

-

LEVEL 7

OP? (WI-l,

2730.80 2730ilh 2730.66 2710.55 2730.45 2730.33 2730.19 2730.08 2729.9' 2729.77 2729.67 2729.45 272Q.?q 2729.11 P728.92 2728.74 2724.53 2728.33 2728.14 7727.95

BRANCH

o-c '100

u I

-6

=

5

-2 -1

x

5 7

_; . ;

-4 -6 -7 -5 -7 -9 -B -10 -10 -11 -12 -13 -16 -17 -17 -i8

-

3 3 3 x 5 l 6 3 x 5 3 8 + 2 2 x 5 2 x 1 l ;I

6

having larger spin weights are connected by solid curves (-), and the K,, = eoen levels by broken curves (- - -) in Fig. 4. The nature of these deviations is interpreted in terms of local perturbations Fven

though

(ZG), as summarized

alternative

different sets of the effectively eypressinp

The

7 defect,

I. may be obtained

by fitting

them

to

v1 transitions, the present parameters seem to be reasonable for the overall structure of the v1 levels unaffected by local perturba-

tions. The determinable parameters of in Table V. The observed inertia defect ison with the value calculated by Oka force field. The observed value agrees error.

in Table

sets of the v1 parameters

i.e., a higher-order

v1 in Watson’s notation are derived and shown for the Y, state is shown in Table VI in comparand Morino (17) on the basis of the harmonic with the calculated value within the estimated defect

of the planarit!-

condition

as defined

b\.

AXD

Y,

Table

I!‘.

(Lontinued)

Observed

Transitions

c9 2691. P690.6P 2699.06 2645.49 2662.87 2681.43 7677.85 2675.30

9 9 10 II :7 1:

267?.

BANDS Ob‘ H,CO

YS

68

2x2 6 3 -0 -7 l 4 3 6X4 3

71 22 21 *I 25 ES

J

a

9 *II II iP 13 14 is 16 i7 *a

19 20 21 PZ t3 ?Z

a.

n-c

“IV cc*-11

‘I

I

x

4 4 3 3 6 P 3 3

Their

Deviations.

v5

Band

3 z 2 2 1 1

2977. ?h 297*. 17 2977.4: 2979.69 29ei.w 2994. i? P986.?4

2677.73

i

298E.W E99@. 2907. 299q. 2997.17 299”. 3001.41 30??.48 3OPE. 3rm7.67 3Ollq.6~ 3011.~5

H2C0.

*

2 +

41 39 4? k5 44

x x

7 7 ? 7 7

7wL1.32 7Wi.14

48 5*

l

Zb49.09

52

7646.4’ ?hkT.RR

54

766Q.7? 2667.22 7664.67 2662.[18 2659.51 2656.90

77 a7 ‘35

of

37 35

7 l

P x

64

3

Z

27

61

‘*DO

2953.47

2957.34 2953.16 2952.99 2957.79 2952.60 2952.41 2952.15 2951.90 2951.62 2951.40

Sb 01) k7 47 48 51 55 5k 57 57

3 4

l

x

2951.00 2950.76

66 Y 5 58 * 3 68 4

2950.44 2950.14 *949.79 2949.45

73 91 35 13

See

and

.5ot

footnotes

s 1 l

of

3 6 6 4

Table

Yamada and Winnewisser AT,,.,.,. = T’~,,., = r’,.,,, -

,I.

(LO), [Tg(Watson)

-

[~~(Kirchhoff)(&+

+,]/(a,

+ a,,) iBo+ G) -

T~cL]/(@,,+

(B,,).

is also evaluated as shown in Table VI. The determination of the “unperturbed” rotational constants for ~1 must await a detailed analvsis of the resonance interactions. H. l
K, = 1” (J = l-19),

K,‘ = 2d (J = 2-13),

K, = 2c (J = 2-ZO),

h-, = 3’ (J = 3-12),

K, = 4 (J = 4-20).

!C,>= 6 (J = 6&20),

h-u = 7 (J = 7-20).

K,, = 1” (.I = l-16), K, = 3d (J = 3-S),

K,, = 5 (J = S-18),

502

NAKAGAWA,

y’

Ref.

-1.0

YAMADA

AND

0

KUCHITSU

1.0 cm-’ I

A total of 477 transitions belonging to these vs levels were used in the least-squares fit to determine the effective parameters of v5. The band origin (vJ, rotational constants (A”, 8, and c), and two centrifugal distortion constants (A.IR and AK) for the v5 state were determined as adjustable variables, while three centrifugal distortion constants (AJ, 6J, and 8~) for v5 and the ground-state constants were fised. The effective constants thus obtained are listed in Table V along with three times the standard errors. The constants for the vg band were determined with smaller standard errors than were those for the vi band, mainly because of the introduction of higher J and higher K levels. The standard deviation B for the 477 transitions fitted in the analysis, 0.040 cm-‘, is larger than the 8 value for the vl band and attributable mainly to the small systematic deviations for the K, = 6 and 7 levels. The wavenumber deviations of all the v6 band transitions, inclusive of those not used in the least-squares fitting, are listed in Table IV. Figure 5 schematically illustrates the Ka and J dependence of the deviations of the observed v5-state energy levels on the ones calculated with the effective parameters. The K, = evea levels having larger spin weights are connected with solid curves and the Ka = o~l(l levels with broken curves in Fig. 5. A number of local perturbations are

VI AND

Y; BANDS

OF HKO

.503

observed, and the!- are interpreted in terms of the accidental Fermi and Coriolis interactions with the lying combination bands (Id), as summarized in Table 111. The high K levels (K 2 7) of the IQ state are expected to be strongly coupled with the IQ + va and v3 + ~6 levels as a result of the combination effect of the a-type Coriolis interactions and the Fermi resonances in the five band system, vq + v6, v2 + v,, I+,, vg + v6, and v3 + v+ Watson’s determinable constants of the v5 state are derived from the determined spectroscopic parameters, as listed in the lower part of Table V. The inertia defect and the T defect for the v5 state are obtained as listed in Table VI. The observed inertia defect deviates significantly from the theoretical value (17) obtained by a normal coordinate treatment; this is probably attributable to some overall resonance interaction with combination bands, because such an interaction was not taken into account in the theoretical calculation in Ref. (17). The observed T defect for the v5 state, which also appears to be anomalously large, seems to correspond to the large AJK value. This large A.,, value may be interpreted as a decrease of the effective rotational constant Beff(K,,) IL each R, subband with the increase in IL. This kind of A, dependence is compatible with the third-order Coriolis interaction between v5 and VI + vl as a result of the fivelevel interaction mentioned above. Hence, a further assignment of high K levels of Y:, and combination bands and a detailed analysis of the complex interactions are desirable.

&dy

Table

Effective

V.

>lolecular

Constants

“.

for

‘“,

and

il

2843.347115)

Li

ii0

9.2498(4X)

9.?237(li)

tl.4uiJ;Y

b

1.29681(56)

1.1936U(li)

l.:!i543:

2

1.13208(15)

l.l3034(1U)

1.1341”’

LJX1U4

0.0255X=

U.U2558

(0, 111558

“JKxlu4

u.67(19)

I.1741421

I1 4 3 II? 2

;p04

7.1(12)

6.58(36J

3.4583

LI,I3 4 9 1

:po4

0.00348C

o.oo348c

I,

: pl4

0.3434c

0.3434’

1.3434

*d

0.019

0.040

ilatz.on’s

determinable

constants

OC

9.2498(48J

9.2237(1:)

w

1.29681(50)

1.‘9366(1:)

c

1.13?22(15)

‘aaaa*lO4

l.l3053(lUJ

-31.2(49)

-31.1(14)

‘bbbb-; ‘ccccx10

-U.l3U

-0.13oc

-o.u:45c

-U,fl7455

Tii104

-?.97iTb)

-5.UUjl;)

1 .eAlOJ

-U.359(8)

-O.S:2iZ)

a

Numbers

in

cr-l-ors I’

c d e

i:hu

31. to

Standard In

parentheses

111 unlta

et

Fixed

of

indicate the

last

three

times

the

diEits.

14). the

iralues

deviation

Flrchhoff’s

(cm

,.S.b

‘4 _

2782.487(14)

dj

for in

notation

the tte

ground least-squares

(E):

state

~onstanta. fit.

:,=l~(h~tjon)liLt+~C). _ _

standard

-1 ,a

504

I

I’ ‘I d

/ ,‘d I I

/ /’ /’ /’

, ,,’

/’ / I

,,‘2 i

IIl--lJ’=O

5

IO

15

20

25

-I

30

1:1c. 1. Perturbation shifts of the Y, band energy levels: Deviations of energy levels from the ones calculated by use of the effective rotational constants. i--_) for the I& = odd levels and (- - -) for the I;,’ = ewz levels.

The hiqh-resolution spectrum observed in the present study estends so widely that it is not practicable to show the present assignment in its full length. Hence, only two small sections of the spectrum are illustrated. Figure 6 shows a section of the P-branch region of the ~1 band, where the spectral structure is relatively simple. Figure 6C is a reproduction of the observed absorption spectrum in the wavenumber linear scale; in this region the base line corresponding to 100% transmission goes down slightly towards low wavenumbers. The ~1 band spectrum which is simulated with the effective constants listed in Table L’ is plotted in Fig. 6A as a line spectrum. In Fig. 6R the perturbed vl band structure is shown in the same wa!‘.

Y, AND

Y> BANDS

50.5

OF H&O

1 J’=O

5

IO

15

FIG. 5. Perturbation shifts of the YZband energy for the K,’ = odd levels.

20 levels.

25 c---j

30

35

for the ii,’ = ewx levels and

(

-1

The “YK (9) transitions, as an example, are marked; the wide spread of the K structures are due to a large negative value of AI-A O. Figure 6E, on the other hand, shows the unperturbed vg band structure which is calculated with the effective parameters listed in Table V. The pP3, “PI, and “Ps branches appear in this region. Since the I(, = 3d (v5) levels are coupled with the k;z = 1’ (VP+ ~4) levels by a Coriolis interaction, the J’P~c branch of the v5 band are perturbed, as shown by the horizontal arrows in Fig. 6E. Corresponding to each of the PPJ(9)c, PP4(lO)c, and PP4(11)~ transitions, an extra peak is observed and assigned as the perturbation-enhanced transition of KU = lr (v~ + v4) +K,, = Gc (G.S.) (14). The structure of the ~1 and I+,bands in this wavenumber region can be understood more readily in the Loomis-Wood diagrams shown in Figs. 2 and 3. Though most of the observed peaks appearing in Fig. 6C are identified by superposing the v1 and v5 band spectra (Figs. 6B and 6D), yet not a small number of observed peaks are left unassigned; combination bands (vs + ~6, VP+ yl, etc.) are the most probable candidates for these assignments. The Q-branch region of the v1 band is illustrated in Fig. i as the second example of the spectrum. The observed spectrum is reproduced in Fig. SC. The unperturbed @-branch structure of the ~1 band is simulated b?. use of the rotational parameters listed in Table \and is plotted in Fig. ?A. This a-type Q branch has a widespread K structure with intensity alternations of 1:3 for k’,” = even:odd. Each QQKbranch has the J structure degrading towards the low-wavenumber side. In the observed spectrum, “QK branches for K” 6 6 can easily be identified with the aid of those in the simulated spectrum, whereas those for K” 2 7 are much distorted because of the perturbations. According to the present analysis, the K,’ = 7 levels of v5 are pushed down as shown by the horizontal arrows in Fig. 7A, and the qQ7 subband is spread into the J structure as illustrated in Fig. 7B. The upper levels of the qQ8and Qg branches are shifted so much

506

NAKAGAWA,

YAMADA

AND

KUCHITSU

508

NAKAGAWA,

YAMADA

AND

KUCHITSU

by perturbations towards high wavenumbers (Fig. 7B) that the observed “Qs and qQ9 peaks degrade to the high-wavenumber side. The v5 band transitions assigned in this region are illustrated in Fig. 7D ; they belong to the branches of pP4, pP3, pPz, pP,, and “PO.These ~5 transitions do not deviate much from the wavenumbers calculated with the effective rotational constants. Some weaker vr, transitions which are expected but not yet located are also shown in Fig. 7D with broken lines. Most of the observed peaks in the range of Fig. 7 are identified as superpositions of the v1 and vg bands. The eight peaks observed between the “QJ and “Qb branches of ~1 are assigned to the PQ, transitions of the vz -I- VJband. This PQ, branch of uz + v4 appears anomalously strong by borrowing the intensity of the qQ7 branch of vr as a result of the Coriolis interaction between the K, = 6 (VP+ ~4) and K, = 7 (Y,) levels (14). RECEIVED:

March 2, 1976 KEPEKENCES

1. 2. 3. 4. 5. 6. 7. X. 9. IO. II. 12. 13. 14. 15. 16. 17. 18. 19. 20.

T. OI