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The rotational spectrum of bromochloromethane in the excited state of the BrCCl bending vibration mode
JOURNAL OF MOLECULAR SPECTROSCOPY 137,
104-l 13 ( 1989)
The Rotational Spectrum of Bromochloromethane in the Excited State of the BrCCl Bending Vibration Mode YUZURLJ NIIDE, HIROKAZU TANAKA, AND ICHIRO OHKOSHI Department of Mathematicsand Physics,NationalDefense Academy. Yokosuka 239, Japan
Microwave spectra in the excited state of the Br-C-Cl bending vibration, v,, for the %“Cl and “Br3’Cl speciesof bromochloromethane have been measured in the frequency region of 1I39 GHz. The b-type R-branch and @branch transitions were assigned.The values of the rotational constants of the excitedstate, v4band, weredetermined to be A = 29 352.425+ 0.029,I3 = 2 131.687 + 0.006, and C = 2010.776 f 0.0 13 MHz for the 7gBr35Cl species,and A = 29 33 1.945 + 0.030, B = 2113.297 2 0.007, and C = 1994.324 f 0.015 MHz for the “Br3’Ci species. From the hypcrfme splittings of the “Br, *‘Br and 35Clnuclei, the nuclear quadrupole coupling constants in the excited state weredetermined m be X, = 386.09 f 0.81, XB = -77.44 + 0.50, X, = -308.65 + 0.95, and 1X&I = 370.92 + 0.60 MHz for 79Br;X, = -35.32 f 0.59, Xbb= -4.94 + 0.32, Xoc = 40.26 f 0.67, and 1x&) = 5 1.7 + 2.2 MHz of 35Clfor the 7gBr35Cl species;X, = 322.78 + 0.63, xbb = -65.10 f 0.35, xn = -257.68 + 0.72, and IX&[ = 312.43 + 0.79 MHz for *‘Br; and X, = -35.62 + 0.43, Xbb= -4.83 f 0.24, x, = 40.45 f 0.49, and )x&l = 54.6 + 1.5 MHz of 35Cl for the 8’Br35Clspecies, respectively. The Br-C-Cl bending vibrational frequency of bromochloromethane was estimated to be 220 cm-’ from the relative intensity measurements and was measured to be 224.3 + 0.2 cm-’ in the gas phase by Raman spectroscopy. 0 1989Academic Resr, Inc.
INTRODUCTION
The microwave spectra of bromochloromethane in the ground vibrational state for the 79Br35CI,8’Br35C1,79Br37C1,and 8’Br37C1species were observed and analyzed to determine the molecular constants discussed in the previous paper ( I ) . The vibrational infrared and Raman spectra of the five-atomic molecules with general formulas of X-CHz-X and X-CH2-Y have been described in detail by Herzberg (2). Bather and Wagner (3) and Wagner (4) have investigated many molecules in the liquid state by Raman spectroscopy. The absorption spectrum of the X-CHz-X molecule by infrared and Raman spectroscopy has also been measured by Emschwiller and Lecomte (5). The u4 vibration which is one of the nine fundamentals of the XCH2-X and X-CH2-Y molecules corresponds to the bending vibration of X-C-X and X-C-Y. The authors have successfully determined the vibrational frequency of u4 of chloroiodomethane in the gas phase by microwave spectroscopy and Raman spectroscopy (6). The purpose of the current work is to extend the analysis of the rotational spectrum of bromochloromethane to the excited state and to give frequency measurements and assignments of the u4 band to the Br-C-Cl bending vibration of CHzBrCl molecule by microwave spectroscopy and Raman spectroscopy in the gas phase. 0022-2852189$3.00 copyright 8 1989 by AcademicRUS, Inc. All rightsof reproductionin any form rcsrvcd.
104
v, BAND OF BROMOCHLOROMETHANE EXPERIMENTAL
105
DETAILS
The sample of bromochloromethane was commercially purchased from Tokyo Kasei Co., and was trap-to-trap distilled to remove impurities below room temperature. The microwave spectra were observed in the frequency region of 11 to 39 GHz on a conventional lOO-kHz square-wave Stark modulation microwave spectrometer and recorded with a strip chart recorder. The 3-m-long absorption cell was cooled by refrigeration to keep a constant temperature of -70°C. The sample pressure ranged from 20 to 30 mTorr. Relative intensities of the absorption lines were measured at -70°C by the technique developed by Esbitt and Wilson ( 7). The measurements of the v4band of the Raman spectrum of bromochloromethane in the gas phase were taken in the frequency region of 150 to 300 cm-’ at room temperature. The apparatus used was a double monochromator JASCO NR-1100. ROTATIONAL
SPECTRA IN THE EXCITED VIBRATIONAL STATE
Studies of the spectra in the excited vibrational state of the present molecule were carried out in the same way as in the case of the ground state. To obtain a contour of the excited state spectra due to the Br-C-Cl bending vibration, preliminary model calculations were made using the plausible structural parameters of bromochloromethane obtained in the previous paper ( 1) . Furthermore, the molecular constants of chloroiodomethane obtained from the analysis of the spectra in the ground vibrational state and excited vibrational state provided useful and convenient information. Consequently, the excited vibrational state transitions were easily assigned because the appearance of the satellite spectra is similar to that of the ground state spectra. The strong b-type Q-branch J1,J_l + Jo,~ transitions with J = 9 to 14 (except J = 10) for the 79Br35C1and *‘Br3%1 species were first assigned on the high-frequency side of the ground state transitions with the help of their characteristic quadrupole hyperhne splittings. For these transitions, all sixteen quadrupole hyperfine splittings were fortunately observed without overlapping the ground state transitions spectra and any other transitions spectra. Because of the large effect made by the second-order corrections, 1O1,9* 100,~~and 61,5 + 60.6transitions were finally assigned, although with difficulty. For the b-type R-branch transitions, the JoJ + J - 1lJ_, transitions with J = 11 to 14 were easily assigned on the low-frequency side of the ground state transitions in spite of the weakness of the line intensity. For these transitions, all of the 16 quadrupole hype&e components could not always be observed because of overlapping by the spectra of the other transitions. Some low J b-type R-branch transitions in the J,_, + J - 10,J_lseries were finally assigned with much difficulty. For the 79Br37Cland *‘Br3’C1species, the weak spectra are attributable to the natural abundance of 37C1nucleus relative to 35Clnucleus, and the low J JI+, 6 JoJ transitions often overlap with the ground vibrational state transitions. The Jos c J - 11,5_1 transitions were not observed even though the conditions of measurements were intentionally changed in many ways to obtain the optimum condition to observe them. Table I shows the assigned transitions of the excited vibrational state for the 79Br35C1 and 8’Br35C1species of bromochloromethane. The rotational constants, centrifugal distortion constants, and values of the elements
106
NIIDE, TANAKA, AND OHKOSHI TABLE I Observed Transitions and Calculated Hypothetical Unsplit Frequencies of Bromochloromethane in the Excited Vibrational State (MHz) Transition + J K;K;
79Br35Cl species
81Br35C1 species
JK_K+
11.1 +
00,o
+
10.1
35 385.218 *
35 315.389
31,3 +
20.2
39 346.933
39 245.173
+
61,s
12 058.771
11 717.041
100,lO +
91,9
16 689.338
16 305.816
110,ll * 101.10
21 362.639
20 936.920
120,12 + 111.11
26 075.319
25 607.104
130.13 + 121,12
30 823.765
30 312.865
21,2
90,9
140,14 + 131.13
35 050.472 27 337.777
11.0 +
10.1
+
20.2
27 463.423
27 457.450
30,3
27 646.607
27 637.689
40.4
27 892.256
27 879.368
51,4 +
50.5
28 201.571
28 183.648
61,5 +
60.6
28 576.048
28 551.979
70,7
29 017.473
28 986.092
81.7 +
80,s
29 527.919
29 487.992
*
90,9
21,l
31.2 + 41.3
71.6
+
-
30 109.735
30 059.957
101,9 + 100,lO
30 765.534
30 704.519
111,lO A 110.11
31 498.182
31 424.456
121,ll + 120,12
32 310.774
32 222.771
91.8
a
35 604.126 27 341.803
131.12 + 130,13
33 206.616
33 102.671
141,13 + 140,14
34 189.188
34 067.537
Calculated using the rotational constants and centrifugal distortion constants listed in Table II.
of the x tensor of the chlorine and bromine in the excited vibrational state were simultaneously determined using the same least squares fitting procedure as was used for those of the ground state ( I ). The constants obtained for the 79Br35C1and *‘Br3%1 species are listed in Table II. Table III shows the correlation coefficients of the final constants for 79Br35C1species in the excited vibrational state. The quadrupole hyperhne component frequencies of the excited vibrational state totaled 250 for the 79Br35C1 species and 244 for the 81Br35Cl species. The hypothetical unsplit frequencies and quadrupole hyperhne component frequencies were then calculated by the direct diagonalization method in the rigid rotor basis using the derived molecular constants of the excited vibrational state of the present molecule. Several selected transitions with observed and calculated frequencies of quadrupole hyperfine components are given in Table IV.
107
vq BAND OF BROMOCHLOROMETHANE TABLE II Rotational Constants, Centrifugal Distortion Constants, and Quadrupole Coupling Constants of Bromochloromethane in the Excited Vibrational State 7gBr35C1
29
species
A
(MHZ)
B
(MHZ)
2131,687(
C
(MHZ)
2010.776(13)
DJ
(kNz)
DJK
(WiZ)
352.425(29)
*lBr35C1
*
species
29 331.945(30)
6,
2113.297(
-0.080(41)
-0.130(46)
-76.8(23)
-77.7(Z)
xaa
(Sr)
(MHz)
386.09(91)
322.78(63)
xbb
(Br)
(mz)
-77.44(50)
-65.10(35)
(MHz)
370.92(60)
3X.43(79)
/xabl(Sr) x,,
(Cl)
(MHZ)
-35.32(59)
-35.62(43)
Xbb
(Cl)
(MHZ)
-4.94(32)
-4.83(24)
IX,bl(Cl)
(HHZ)
51.7(22)
N
b
RMS
a
54.6(15)
250 c
in parentheses
Figures from
2.5
last
figure.
b
Number
c
Root
times
the
of observed
mean
244
0.008
(MHZ)
square
0.007
indicate
standard
uncertainties
deviations
frequencies deviation
7)
1994.324(1.5)
used
of the
ASSIGNMENT OF THE Br-C-Cl
calculated
attached
in the
to the
calculations.
flt.
BENDING VIBRATION
Relative intensities of transitions for the 79Br35C1species of bromochloromethane were compared for the several b-type Q-branch transitions to obtain the vibrational TABLE III Correlation Coefficients of Final Spectroscopic Constants of 7gBr’5ClCHz in the Excited Vibrational State A
1.00
B
-0.05
1.00
C
-0.22
0.93
1.00
0.44
-0.50
-0.78
DJ D JK
1.00
0.42
-0.75
-0.93
0.94
1.00
x,,(Sr)
-0.01
0.07
0.07
-0.05
-0.07
1.00
xbb(Br)
0.01
-0.06
-0.06
0.04
0.06
-0.98
1.00
xab(Br)
0.15
0.14
0.14
-0.10
-0.11
-0.11
0.11
1.00
X,,(Cl)
-0.00
0.16
0.17
-0.14
-0.16
-0.45
0.46
0.08
1.00
Xbb(C1)
-0.00
-0.16
-0.17
0.13
0.15
0.40
-0.41
-0.07
-0.94
1.00
xab(cl)
0.06
-0.00
-0.01
0.01
0.01
0.03
-0.03
-0.20
-0.02
0.00
1.00
108
NXIDE, TANAKA, AND OHKOSWI TABLE IV Observed Frequencies of Hyperfine Components of the Transitions of Bromochloromethane in the Excited Vibrational State (MHz) Transition
F(F1
)+
"d5C1
species
ohs.
F'( F1')
Aa
%r35Cl obs.
sl)ecies
b
loo,10* 91.9 26/2(23/Z)
+ 24/2(21/Z)
24/2(23/Z)
. 22/2(21/2)
22/2(23/Z)
+ 20/2(21/Z)
20/2(23/2)
+ 16/2(21/Z)
24~2(2112)
+ 22/2(19/2)
22/2(21/2)
696.38 701.21 700.31 695.73 674.26
-0.169 -0.051 -0.174 -0.109 -0.078
16/2(17/Z) 16/2(17/Z) 14/2(17/Z) 18,'2(15j2) 16/2(15/Z) 14/2(15/a) 12/2(15/Z)
311.39
-0.099
16 316.27
0.050 315.36 -0.076 310.65 -0.136 292.77 -0.151 296.39* -0.166 296.39* -0.142 291.81 -0.230 297.72 -0.129 301.38 -0.057 300.52 -0.146
16 683.44 -0,154 16 662.62 -0.192 16 702.53 -0.168 16 707.27 -0.072 16 706.15 -0.119
16 321.15 -0.067 16 320.06 -0.064
+
2012(19/2) + 16/2(19/Z) * 16/2(19/Z) + 20/2(17/2) L 16/2(17/2) 16/2(17/Z) + 14/2(17/Z) *
18
16 16 16 16 16 16 16 16 16
f 20/2(19/Z)
18/2(19/Z) 16/2(21/z) + 16/2(19/Z) 22/2(19/Z) + 20/2(17/Z) 20/2(21/2)
16 16 16 16 16
16 673.45 -0.016
l20,12 + 111,11 30/2(27/Z) * 26/2(27/2) + 26/2(27/Z) + 24/2(27/Z) + 26/2(25/2) + 26/2(25/2) + 24/2(25/2) + 22/2(25/2) + 26/2(23/Z) f 24/2(23/Z) * 22/2(23/Z) + 20/2(23/z) + 24/2(21/a) + 22/2(21/2) + 20/2(21/Z) + 18/2(21/2) L
28/2(25/2) 26/2(25/Z) 24/2(25/2) 22/2(25/2) 26/2(X/2) 24/2(a3/2) 22/2(23/2) 20/2(23]2) 24/2(21/Z) 22/2(21/Z) 20/2(21/2) 16/2(21/z) 22/2(19/2) 20/2(19/2) 18/2(19/Z) 16/2(19/Z)
26 26 26 26 26 26 26 26 26
060.69 063.73* 064.43 059.92 063.73* 066.92 066.02 061.67 095.56
26 064.76
0.130 0.141 0.145 0.107 -0.003 0.177 -0.051 0.106 0.063
0.154
25 25 25 25
613.33 0.246 617.96 0.260 617.18* 0.245 612..58* 0.176
25 25 25 25 25 a5 a5 a5 25 25 25 25
594.52 0.113 600.71 0.125 598.06' 0.039 593.85 o.aea 592.21 0.158 598.08* -0.093 597.65 0.227 593.07 0.126 611.47 0.124 615.66 0.057 614.62 -0.012 610.39 -0.017
35 35 35 35 35
056.40 060.78 660.33 055.66 038.18
l40,14 + 131,13 34/2(31/Z) 32/2(31/2) + 30/2(31/Z) * 26/2(31/2) + 32/2(29/2) + 30/2(29/Z) + 26/2(29/a) . 26/2(29/2) f 30/2(27/2) + 29/2(27/z) + 20/2(27/2) + 24/2(27/Z) +
* B
Not
32/2(29/2) 30(2(29/2) 28/2(29/Z) 26/2(29/2) 30/2(27/Z) 26/2(27/Z) 26/2(27/Z) 24/2(27/Z) 26/2(25/2) a6/2(25/2) 24/9(25/Z) 22/2(25/2)
resolved. A = obs. - talc.
35 35 35 35
611.61 616.09 615.58 611.14
-0.103 -0.061 -0.049 -0.065
-0.079 -0.161 -0.087 -0.134 -0.110
35 596.53* -0.103 36 593.58 -0.170 35 037.57 -0.136 35 597.09 -0.110 35 596.534 -0.137 35 592.22 -0.075
vq BAND OF BROMOCHLOROMETHANE
109
TABLE IV-Continued Transition F(
Fl)+
140,14
F'(
79rw35Cl ohs.
Fl')
species B
8h35Cl ohs.
sptx.ies &
* 131,13
a8/2(25/2)
f 26/2(13/Z)
36 615.32
-0.022
35 059.46
-0.071
26/2(25/Z)
+ 24/2(23/2)
35 619.73
-0.027
35 063.84
-0.125
24/2(25/Z)
+ 22/2(23/Z)
35 618.93
-0.177
35 063.20
-0.114
22/2(25/2)
* 20/2(23/2)
35 615.62
-0.064
35 058.74
-0.129
51,4
*
50,5
16/2(13/2)
* 16/2(13/Z)
28 215.96
-0.038
28 194.85
-0.109
14/2(13/2)
* 14/2(13/2)
28 222.11
0.000
28 201.08
-0.050
12/2(13/2)
+ 12/2(13/Z)
28 220.83
0.070
10/2(13/2)
f 10/2(13/2)
28 214.56
-0.163
28 193.65
-0.036
14/2(11/2)
* 14/2(11/2)
28 176.13'
-0.142
28 162.00
-0.031
12/2(11/2)
+ 12/2(11/2)
28 181.70
0.059
28 167.43
0.088
10/2(11/2)
* 10/2(11/Z)
28 180.26
-0.124
28 165.98
-0.163
+
28 174.61
-0.053
28 160.34
-0.052
28 172.19
-0.027
28 177.47
-0.102
8/2(11/Z)
S/2(11/2)
12/2(
9/2)
+ 12/2(
9/2)
10/2(
9/2)
+ 10/2(
9/Z)
28
193.96
-0.028
8/2(
S/2)
c
8/2(
9/2)
28 192.44
0.030
6/2(
S/2)
.. 6/2(
9/2)
10/2(
7/2)
* 10/2(
7/2)
28 226.55
-0.083
28 176.13*
0.086
28 170.12
0.101
28 203.96
-0.107 -0.139
8/2(
712)
+
8/2(
712)
28 232.69
-0.014
28 209.98
6/2(
712)
c
6/2(
712)
28 230.40
0.085
28 207.76
0.016
4/2(
712)
+
4/2(
712)
28 224.19
0.059
28 201.51
-0.046
20/2(17/2)
* 20/2(17/2)
28 994.62
0.029
18/2(17/2)
+ 18/2(17/2)
29 000.21
-0.069
16/2(17/2)
+ 16/2(17/2)
29 033.28
-0.048
28 999.62
-0.116
14/2(17/2)
. 14/2(17/2)
29 026.69
-0.029
28 992.69
-0.027
M/2(15/2)
+ 18/2(15/2)
28 982.54
-0.109
28 950.82
-0.028
16/2(15/2)
+ 16/2(X1/2)
28 989.16
-0.014
28 957.66
-0.019
14/2(15/a)
* 14/2(15/2)
28 988.21
-0.005
28 956.78
-0.069
12/2(15/2)
+ 12/2(15/2)
26 980.77
-0.107
28 948.64
0.052
16/2(13/2)
* 16/2(13/Z)
28 999.22
0.087
14/2(X3/2)
+ 14/2(13/2)
29 003.53
-0.042
28 973.498
0.096
12/2(13/2)
.- 12/2(13/2)
29 002.92
-0.044
28 973.49*
-0.109
10/2(13/2)
* 10/2(13/2)
28 997.41
0.100
28 967.62
-0.015
14/2(11/2)
. 14/2(11/Z)
29 016.46
-0.103
12/2(11/2)
* 12/2(11/2)
29 019.50
0.055
10/2(11/2)
* 10/2(11/2)
29 019.12
0.106
e/2(11/2)
*
8/2(11/2)
29 015.02
-0.155
'1.8
+
So,9
24/2(21/2)
+ 24/2(21/Z)
30 121.26
0.005
30 069.18
0.056
22/2(21/2)
+ 22/2(21/2)
30 127.61
0.077
30 075.43
0.025
20/2(21/Z)
+ 20/2(21/2)
30 126.69
0.034
30.074.52
-0.006
18/2(21/2)
f 18/2(21/Z)
30 120.37
-0.025
30 068.24
-0.025
22/2(19/2)
* 22/2(19/Z)
30 086.87
0.026
30 040.51
-0.010
20/2(19/2)
+ 20/2(19/Z)
30 092.80
0.177
30 046.24
0.099
18/2(19/2)
* 18/2(19/2)
30 092.12
0.143
30 045.77
0.120
16/2(19/2)
+ M/2(19/2)
30 085.88
0.064
30 039.51
0.030
20/2(17/2)
* 20/2(17/Z)
30 092.53
0.027
30 045.54
0.036
18/2(17/2)
f 18/2(17/Z)
30 098.07
-0.021
30 651.01
0.073
NUDE, TANAKA,
110
AND OHKOSHI
TABLE IV-Continued Transition F(F1)+
%,a*
F'( Fl')
'gBr35C1 swcies d ohs.
'lBr3%1 6wcies obs. b
go.9
n3/2ti7fa)+ iefa(i7fa)
so 097.16
14/2(17/Z) + 18/2(15/Z) + 16/2(15/Z) + 14/2(15/2) + 12/2(15/2) +
30 30 30 30 30
091.28 126.23 132.29 131.16 125.14
-0.061 0.113 0.006 0.007 0.017 0.114
30 30 30 30 30 30
050.04 -0.032 043.89 -0.110 073.43 0.046 079.49 0.041 078.32 0.009 072.21 0.033
31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31
510.16 516.60 515.87 509.41 475.92 481.86 461.28 475.01 481.14 486.86 486.12 479.91 514.78 521.08 520.04 513.77
0.017 0.063 0.087 -0.003 0.037 0.108 -0.056 -0.014 0.061 0.016 0.026 0.076 0.078 0.102 -0.005 0.036
31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31
433.95 -0.001 440.39 0.043 439.63 0.029 433.24 0.017 405.53 0.054 411.03* -0,010 411.03' 0.102 404.66 0.050 410.11 -0.057 415.64 0.013 414.85 -0.039 408.64 0.028 437.84 0.046 444.13 0.060 443.12 -0.019 436.80 -0.018
33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33
219.04 -0.008 225.62 -0.004 224.96 0.000 218.39 -0.005 184.14 -0.083 190.04* -0.084 190.04* 0.053 183.45 -0.016 188.86 -0.007 194.67 -0.028 194.06 0.029 187.53 -0.010 222.87 0.019 229.42 0.074 228.56 0.020 221.98 -0.036
33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33
112.54 0.016 119.12 0.022 118.44 0.007 111.85 -0.023 083.56 -0.035 091.31 0.019 089.33 -0.025 082.82 -0.013 085.73 -0.015 093.37 -0.002 092.69 -0.023 086.26 0.047 115.76 0.030 122.26 0.036 121.52 0.099 114.89 -0.002
34 34 34 34 34 34 34 34
201.78 -0.087 208.47 -0.090 207.87 -0.056 201.18 -0.061 166.54 -0.058 172.36* -0.063 172.36* -0.158 165.83 -0.047
33 33 33 33 33 33 33 33
112.54 119.12 118.44 111.85 063.56 091.31 089.33 082.82
14/2(17/Z) 18/2(15/Z) M/2(15/2) 14/2(15/2) 12/2(15/Z)
111.10 + 110,ll 28/2(25/2) + 26/2(25/2) + 24/2(25/2) + 22/2(25/2) + 26/2(23/2) + 24/2(23/2) + 22/2(23/2) + 20/2(23/2) + 24/2(21/2) + 22/2(21/2) + 20/2(21/2) + M/2(21/2) + 22/2(19/2) + 20/2(19/2) + 18/2(19/Z) + E/2(19/2) +
28/2(25/2) 26/2(25/2) 24/2(25/2) 22/2(25/2) 26/2(23/2) 24/2(23/Z) 22/2(23/2) 20/2(23/2) 24/2(21/2) 22/2(21/2) 20/2(21/2) M/2(21/2) 22/2(19/2) 20/2(19/2) 18/2(19/Z) M/2(19/2)
131,12 + 130.13 32/2(29/2) + 30/2(29/2) + 28/2(29/Z) + 26/2(29/2) + 30/2(27/2) + 28/2(27/2) + 26/2(27/2) + 24/2(27/2) + 28/2(25/2) + 26/2(25/2) + 24/2(25/2) + 22/2(25/2) + 26/2(23/2) + 24/2(23/2) + 22/2(23/2) + 20/2(23/2) +
32/2(29/2) 30/2(29/Z) 29/2(29/2) 26/2(29/2) 30/2(27/2) 28/2(27/2) 26/2(27/2) 24/2(27/Z) 28/2(25/2) 26/2(25/2) 24/2(25/2) 22/2(25/2) 26/2(23/2) 24/2(23/2) 22/2(23/2) 20/2(23/z)
141,13 + 140,14 34/2(31/2) + 32/2(31/2) + 30/2(3112) + 28f2(3112) + 32/2(29/2) + 30/2(29/2) + 28/2(29/Z) + 26/2(29/Z) +
34/2(31/2) 32/2(31/2) 30/2(31/2) 28/2(X/2) 32/2(29/2) 30/2(29/2) 28/2(29/2) 26/2(29/Z,
-0.077 -0.157 -0.150 -0.091 -0.034 -0.054 -0.046 -0.046
vq BAND
111
OF BROMOCHLOROMETHANE TABLE IV-Continued 7gBr35C1
Transition F(
F1)
*
141.13
F'(
0bS.
Fl')
%r35Cl
species
A
ohs .
species
*
+ l40,14
30/2(27/Z)
+ 30/2(27/Z)
34 171.12
-0.057
33 085.75
-0.037
28/2(27/2)
+ 28/2(27/2)
34 176.79
-0.149
33 093.37
-0.074
26/2(27/2)
+ 26/2(27/2)
34 176.25
-0.053
33 092.69
-0.093
24/2(27/2)
+ 24/2(27/2)
34 169.64
-0.049
33 086.26
-0.143
28/2(25/2)
+ 28/2(25/2)
34 205.28
-0.062
33 115.76
-0.054
26/2(25/2)
+ 26/2(25/2)
34 211.91
-0.043
33 122.26
-0.112
24/2(25/2)
+ 24/2(25/2)
34 211.13
-0.065
33 121.52
0.007
22/2(25/Z)
+ 22/2(25/2)
34 204.47
-0.086
33 114.89
-0.052
energy difference between the ground and the excited state. The number of transitions used was six: 51,4f 50,5, & f 60,6, 7l,6 + 70,7, g1,7+ go,8, 91,s f 90,9, and 10~ f 10o,ro. Each of the spectra to be measured had to be isolated since overlapping spectra cannot be used in relative intensity measurements. The absorption cell was cooled by refrigeration to keep a constant temperature of -70°C throughout the measurements. The average value of the intensity ratio is 0.200 for the excited state to the ground state. This ratio leads to a vibrational energy difference of 220 cm-‘. The spectra of bromochloromethane are so close and crowded that the measured intensity of a line is naturally affected by other lines. The uncertain results from intensity measurements are due mainly to the weakness and distorted Iineshapes of the observed spectra. In addition, the splittings of the b-type Q-branch transitions are large, and two corresponding tines for the ground and excited vibrational state he a few hundred megacycles apart from each other. The intensity measurements of the spectra of the b-type Q-
300
200
250
150
cm-1 FIG.
1.Raman spectrum of bromochloromethane
in gas phase.
NIIDE, TANAKA, AND OHKOSHI
112
branch transitions could not be performed, and so the total uncertainty will exceed 20%. The u4 band frequency of bromochloromethane in the gas phase was determined to be 224.3 cm-’ by Raman spectroscopy (Fig. 1). The uncertainty was estimated to be k0.2 cm-‘. The derived vibrational energy difference in the microwave study is 220 cm-‘. This assignment performed by microwave spectroscopy is considered to be in agreement with that made by Raman spectroscopy.
TABLE V Nuclear Quadrupole Coupling Constant Tensor of Bromochloromethane in the Inertial System and the Principal System in the Excited Vibrational State 79
Br35 Cl species
*1Br35C1 species
x,, (WZ)
386.09(61) 8
322.?6(63)
Xbb (WZ)
-77.44(50)
-65.10(35)
xc, (mz)
-306.65(95)
-257.66(72)
IX,bI(W xzz (YAz)
370.92(60)
312.43(79)
591.70
496.57
XYY (mz)
-309.65
-257.66
x,, (mz)
-263.05
-236.89
25.60
16.79
Ab UC d % 7gBr/61Br e
0.04326
0.03763
0.59665
0.59662 1.1916
Chlorine x,, (Wz)
-35.32(59)
-35.62(43)
Xbb (UMZ)
-4.94(32)
-4.93(24)
Xcc (az)
40.26(67)
40.45(49)
Ixabl(w x,, (Iwz)
51.7(22)
54.6(15)
-74.01
-76.95
XYY (MZ)
40.26
40.45
xix (wlz)
33.75
36.50
A
-6.51
-3.95
0.08796
0.05133
1.27972
1.27119
Figures in parentheses indicate the uncertainties attached to the last significant figures calculated from 2.5 times the standard deviation. A = x,, - xYY' n = (x,, - XYY)/X,,. ?I = (Xbb - xoc)lx,,. The reported ratio of the quadrupole moments 7gBr and 9lBr nuclei is 1.19707.
“4 BAND OF BROMOCHLOROMETHANE
113
DISCUSSION
In the present microwave study, the rotational transitions of bromochloromethane in the excited vibrational states for both 79Br35C1and 8LBr35C1species have been measured and relative intensity measurements have also been carried out. According to the results of Wagner (4), the v4 vibrational frequency of bromochloromethane was determined to be 227 cm-‘. The vibrational energy difference and frequencies of 220 and 224.3 cm-’ of bromochloromethane in the gas phase determined by microwave and Raman spectroscopy in this study agree well with 227 cm-’ value. We therefore conclude that the excited vibrational state transitions observed and analyzed are probably due to the Br-C-Cl bending vibration of the present molecule. As for the elements of the x tensor in the excited vibrational state, the values in the principal axes system of the quadrupole coupling tensor are obtained by diagonalizing the quadrupole coupling tensor in the principal inertial system. The characteristic values of the x tensor x,, x,, and X,, of 79Br and *‘Br nuclei for the 79Br35C1and B’Br35Clspecies, and x,, X,, and X, of the 35Clnucleus for the “Br3’Cl and 8’Br35Cl species are also given in Table V. The values of the nuclear quadrupole coupling constant tensor in the principal inertial system and principal axes system have nearly the same values as those of the ground state. The electronic structure of the present molecule surrounding the chlorine and bromine nuclei in the excited vibrational state is considered to be unchanged from that of the ground state in spite of the existence of the Br-C-Cl bending vibration. The n value is similar to that in the ground state and indicates that there is no significant deviation from cylindrical symmetry. ACKNOWLEDGMENT
Calculations were carried out at the Computer Center of the National Defense Academy, Japan. RECEIVED:
March 24, 1989 REFERENCES
I. OHKOSHI, J. Mol. Spectrosc., in press. Spectra and Molecular Structure. II. Infrared and Raman Spectra of Polyatomic Molecules,” Van Nostrand, Princeton, NJ, 1945. W. BACHER AND J. WAGNER, 2. Phys. Gem. A&. B43, 191-197 (1939). J. WAGNER, Z. Phys. Chem. Abt. B 45,69-91 (1939). G. EMSCHWILLERAND J. LECOMTE, J. Phys. Les Ulis Fr. 8, 130-144 ( 1937). Y. NIIDE AND I. OHKOSHI, J. Mol. Spectrosc. 128,88-97 ( 1988). A. S. ESBITTAND E. B. WILSON, JR., Rev. Sci. Instrum. 34,901-907 (1963).
I. Y. 2. G. 3. 4. 5. 6. 7.
NUDE AND
HERZBERG, “Molecular
104-l 13 ( 1989)
The Rotational Spectrum of Bromochloromethane in the Excited State of the BrCCl Bending Vibration Mode YUZURLJ NIIDE, HIROKAZU TANAKA, AND ICHIRO OHKOSHI Department of Mathematicsand Physics,NationalDefense Academy. Yokosuka 239, Japan
Microwave spectra in the excited state of the Br-C-Cl bending vibration, v,, for the %“Cl and “Br3’Cl speciesof bromochloromethane have been measured in the frequency region of 1I39 GHz. The b-type R-branch and @branch transitions were assigned.The values of the rotational constants of the excitedstate, v4band, weredetermined to be A = 29 352.425+ 0.029,I3 = 2 131.687 + 0.006, and C = 2010.776 f 0.0 13 MHz for the 7gBr35Cl species,and A = 29 33 1.945 + 0.030, B = 2113.297 2 0.007, and C = 1994.324 f 0.015 MHz for the “Br3’Ci species. From the hypcrfme splittings of the “Br, *‘Br and 35Clnuclei, the nuclear quadrupole coupling constants in the excited state weredetermined m be X, = 386.09 f 0.81, XB = -77.44 + 0.50, X, = -308.65 + 0.95, and 1X&I = 370.92 + 0.60 MHz for 79Br;X, = -35.32 f 0.59, Xbb= -4.94 + 0.32, Xoc = 40.26 f 0.67, and 1x&) = 5 1.7 + 2.2 MHz of 35Clfor the 7gBr35Cl species;X, = 322.78 + 0.63, xbb = -65.10 f 0.35, xn = -257.68 + 0.72, and IX&[ = 312.43 + 0.79 MHz for *‘Br; and X, = -35.62 + 0.43, Xbb= -4.83 f 0.24, x, = 40.45 f 0.49, and )x&l = 54.6 + 1.5 MHz of 35Cl for the 8’Br35Clspecies, respectively. The Br-C-Cl bending vibrational frequency of bromochloromethane was estimated to be 220 cm-’ from the relative intensity measurements and was measured to be 224.3 + 0.2 cm-’ in the gas phase by Raman spectroscopy. 0 1989Academic Resr, Inc.
INTRODUCTION
The microwave spectra of bromochloromethane in the ground vibrational state for the 79Br35CI,8’Br35C1,79Br37C1,and 8’Br37C1species were observed and analyzed to determine the molecular constants discussed in the previous paper ( I ) . The vibrational infrared and Raman spectra of the five-atomic molecules with general formulas of X-CHz-X and X-CH2-Y have been described in detail by Herzberg (2). Bather and Wagner (3) and Wagner (4) have investigated many molecules in the liquid state by Raman spectroscopy. The absorption spectrum of the X-CHz-X molecule by infrared and Raman spectroscopy has also been measured by Emschwiller and Lecomte (5). The u4 vibration which is one of the nine fundamentals of the XCH2-X and X-CH2-Y molecules corresponds to the bending vibration of X-C-X and X-C-Y. The authors have successfully determined the vibrational frequency of u4 of chloroiodomethane in the gas phase by microwave spectroscopy and Raman spectroscopy (6). The purpose of the current work is to extend the analysis of the rotational spectrum of bromochloromethane to the excited state and to give frequency measurements and assignments of the u4 band to the Br-C-Cl bending vibration of CHzBrCl molecule by microwave spectroscopy and Raman spectroscopy in the gas phase. 0022-2852189$3.00 copyright 8 1989 by AcademicRUS, Inc. All rightsof reproductionin any form rcsrvcd.
104
v, BAND OF BROMOCHLOROMETHANE EXPERIMENTAL
105
DETAILS
The sample of bromochloromethane was commercially purchased from Tokyo Kasei Co., and was trap-to-trap distilled to remove impurities below room temperature. The microwave spectra were observed in the frequency region of 11 to 39 GHz on a conventional lOO-kHz square-wave Stark modulation microwave spectrometer and recorded with a strip chart recorder. The 3-m-long absorption cell was cooled by refrigeration to keep a constant temperature of -70°C. The sample pressure ranged from 20 to 30 mTorr. Relative intensities of the absorption lines were measured at -70°C by the technique developed by Esbitt and Wilson ( 7). The measurements of the v4band of the Raman spectrum of bromochloromethane in the gas phase were taken in the frequency region of 150 to 300 cm-’ at room temperature. The apparatus used was a double monochromator JASCO NR-1100. ROTATIONAL
SPECTRA IN THE EXCITED VIBRATIONAL STATE
Studies of the spectra in the excited vibrational state of the present molecule were carried out in the same way as in the case of the ground state. To obtain a contour of the excited state spectra due to the Br-C-Cl bending vibration, preliminary model calculations were made using the plausible structural parameters of bromochloromethane obtained in the previous paper ( 1) . Furthermore, the molecular constants of chloroiodomethane obtained from the analysis of the spectra in the ground vibrational state and excited vibrational state provided useful and convenient information. Consequently, the excited vibrational state transitions were easily assigned because the appearance of the satellite spectra is similar to that of the ground state spectra. The strong b-type Q-branch J1,J_l + Jo,~ transitions with J = 9 to 14 (except J = 10) for the 79Br35C1and *‘Br3%1 species were first assigned on the high-frequency side of the ground state transitions with the help of their characteristic quadrupole hyperhne splittings. For these transitions, all sixteen quadrupole hyperfine splittings were fortunately observed without overlapping the ground state transitions spectra and any other transitions spectra. Because of the large effect made by the second-order corrections, 1O1,9* 100,~~and 61,5 + 60.6transitions were finally assigned, although with difficulty. For the b-type R-branch transitions, the JoJ + J - 1lJ_, transitions with J = 11 to 14 were easily assigned on the low-frequency side of the ground state transitions in spite of the weakness of the line intensity. For these transitions, all of the 16 quadrupole hype&e components could not always be observed because of overlapping by the spectra of the other transitions. Some low J b-type R-branch transitions in the J,_, + J - 10,J_lseries were finally assigned with much difficulty. For the 79Br37Cland *‘Br3’C1species, the weak spectra are attributable to the natural abundance of 37C1nucleus relative to 35Clnucleus, and the low J JI+, 6 JoJ transitions often overlap with the ground vibrational state transitions. The Jos c J - 11,5_1 transitions were not observed even though the conditions of measurements were intentionally changed in many ways to obtain the optimum condition to observe them. Table I shows the assigned transitions of the excited vibrational state for the 79Br35C1 and 8’Br35C1species of bromochloromethane. The rotational constants, centrifugal distortion constants, and values of the elements
106
NIIDE, TANAKA, AND OHKOSHI TABLE I Observed Transitions and Calculated Hypothetical Unsplit Frequencies of Bromochloromethane in the Excited Vibrational State (MHz) Transition + J K;K;
79Br35Cl species
81Br35C1 species
JK_K+
11.1 +
00,o
+
10.1
35 385.218 *
35 315.389
31,3 +
20.2
39 346.933
39 245.173
+
61,s
12 058.771
11 717.041
100,lO +
91,9
16 689.338
16 305.816
110,ll * 101.10
21 362.639
20 936.920
120,12 + 111.11
26 075.319
25 607.104
130.13 + 121,12
30 823.765
30 312.865
21,2
90,9
140,14 + 131.13
35 050.472 27 337.777
11.0 +
10.1
+
20.2
27 463.423
27 457.450
30,3
27 646.607
27 637.689
40.4
27 892.256
27 879.368
51,4 +
50.5
28 201.571
28 183.648
61,5 +
60.6
28 576.048
28 551.979
70,7
29 017.473
28 986.092
81.7 +
80,s
29 527.919
29 487.992
*
90,9
21,l
31.2 + 41.3
71.6
+
-
30 109.735
30 059.957
101,9 + 100,lO
30 765.534
30 704.519
111,lO A 110.11
31 498.182
31 424.456
121,ll + 120,12
32 310.774
32 222.771
91.8
a
35 604.126 27 341.803
131.12 + 130,13
33 206.616
33 102.671
141,13 + 140,14
34 189.188
34 067.537
Calculated using the rotational constants and centrifugal distortion constants listed in Table II.
of the x tensor of the chlorine and bromine in the excited vibrational state were simultaneously determined using the same least squares fitting procedure as was used for those of the ground state ( I ). The constants obtained for the 79Br35C1and *‘Br3%1 species are listed in Table II. Table III shows the correlation coefficients of the final constants for 79Br35C1species in the excited vibrational state. The quadrupole hyperhne component frequencies of the excited vibrational state totaled 250 for the 79Br35C1 species and 244 for the 81Br35Cl species. The hypothetical unsplit frequencies and quadrupole hyperhne component frequencies were then calculated by the direct diagonalization method in the rigid rotor basis using the derived molecular constants of the excited vibrational state of the present molecule. Several selected transitions with observed and calculated frequencies of quadrupole hyperfine components are given in Table IV.
107
vq BAND OF BROMOCHLOROMETHANE TABLE II Rotational Constants, Centrifugal Distortion Constants, and Quadrupole Coupling Constants of Bromochloromethane in the Excited Vibrational State 7gBr35C1
29
species
A
(MHZ)
B
(MHZ)
2131,687(
C
(MHZ)
2010.776(13)
DJ
(kNz)
DJK
(WiZ)
352.425(29)
*lBr35C1
*
species
29 331.945(30)
6,
2113.297(
-0.080(41)
-0.130(46)
-76.8(23)
-77.7(Z)
xaa
(Sr)
(MHz)
386.09(91)
322.78(63)
xbb
(Br)
(mz)
-77.44(50)
-65.10(35)
(MHz)
370.92(60)
3X.43(79)
/xabl(Sr) x,,
(Cl)
(MHZ)
-35.32(59)
-35.62(43)
Xbb
(Cl)
(MHZ)
-4.94(32)
-4.83(24)
IX,bl(Cl)
(HHZ)
51.7(22)
N
b
RMS
a
54.6(15)
250 c
in parentheses
Figures from
2.5
last
figure.
b
Number
c
Root
times
the
of observed
mean
244
0.008
(MHZ)
square
0.007
indicate
standard
uncertainties
deviations
frequencies deviation
7)
1994.324(1.5)
used
of the
ASSIGNMENT OF THE Br-C-Cl
calculated
attached
in the
to the
calculations.
flt.
BENDING VIBRATION
Relative intensities of transitions for the 79Br35C1species of bromochloromethane were compared for the several b-type Q-branch transitions to obtain the vibrational TABLE III Correlation Coefficients of Final Spectroscopic Constants of 7gBr’5ClCHz in the Excited Vibrational State A
1.00
B
-0.05
1.00
C
-0.22
0.93
1.00
0.44
-0.50
-0.78
DJ D JK
1.00
0.42
-0.75
-0.93
0.94
1.00
x,,(Sr)
-0.01
0.07
0.07
-0.05
-0.07
1.00
xbb(Br)
0.01
-0.06
-0.06
0.04
0.06
-0.98
1.00
xab(Br)
0.15
0.14
0.14
-0.10
-0.11
-0.11
0.11
1.00
X,,(Cl)
-0.00
0.16
0.17
-0.14
-0.16
-0.45
0.46
0.08
1.00
Xbb(C1)
-0.00
-0.16
-0.17
0.13
0.15
0.40
-0.41
-0.07
-0.94
1.00
xab(cl)
0.06
-0.00
-0.01
0.01
0.01
0.03
-0.03
-0.20
-0.02
0.00
1.00
108
NXIDE, TANAKA, AND OHKOSWI TABLE IV Observed Frequencies of Hyperfine Components of the Transitions of Bromochloromethane in the Excited Vibrational State (MHz) Transition
F(F1
)+
"d5C1
species
ohs.
F'( F1')
Aa
%r35Cl obs.
sl)ecies
b
loo,10* 91.9 26/2(23/Z)
+ 24/2(21/Z)
24/2(23/Z)
. 22/2(21/2)
22/2(23/Z)
+ 20/2(21/Z)
20/2(23/2)
+ 16/2(21/Z)
24~2(2112)
+ 22/2(19/2)
22/2(21/2)
696.38 701.21 700.31 695.73 674.26
-0.169 -0.051 -0.174 -0.109 -0.078
16/2(17/Z) 16/2(17/Z) 14/2(17/Z) 18,'2(15j2) 16/2(15/Z) 14/2(15/a) 12/2(15/Z)
311.39
-0.099
16 316.27
0.050 315.36 -0.076 310.65 -0.136 292.77 -0.151 296.39* -0.166 296.39* -0.142 291.81 -0.230 297.72 -0.129 301.38 -0.057 300.52 -0.146
16 683.44 -0,154 16 662.62 -0.192 16 702.53 -0.168 16 707.27 -0.072 16 706.15 -0.119
16 321.15 -0.067 16 320.06 -0.064
+
2012(19/2) + 16/2(19/Z) * 16/2(19/Z) + 20/2(17/2) L 16/2(17/2) 16/2(17/Z) + 14/2(17/Z) *
18
16 16 16 16 16 16 16 16 16
f 20/2(19/Z)
18/2(19/Z) 16/2(21/z) + 16/2(19/Z) 22/2(19/Z) + 20/2(17/Z) 20/2(21/2)
16 16 16 16 16
16 673.45 -0.016
l20,12 + 111,11 30/2(27/Z) * 26/2(27/2) + 26/2(27/Z) + 24/2(27/Z) + 26/2(25/2) + 26/2(25/2) + 24/2(25/2) + 22/2(25/2) + 26/2(23/Z) f 24/2(23/Z) * 22/2(23/Z) + 20/2(23/z) + 24/2(21/a) + 22/2(21/2) + 20/2(21/Z) + 18/2(21/2) L
28/2(25/2) 26/2(25/Z) 24/2(25/2) 22/2(25/2) 26/2(X/2) 24/2(a3/2) 22/2(23/2) 20/2(23]2) 24/2(21/Z) 22/2(21/Z) 20/2(21/2) 16/2(21/z) 22/2(19/2) 20/2(19/2) 18/2(19/Z) 16/2(19/Z)
26 26 26 26 26 26 26 26 26
060.69 063.73* 064.43 059.92 063.73* 066.92 066.02 061.67 095.56
26 064.76
0.130 0.141 0.145 0.107 -0.003 0.177 -0.051 0.106 0.063
0.154
25 25 25 25
613.33 0.246 617.96 0.260 617.18* 0.245 612..58* 0.176
25 25 25 25 25 a5 a5 a5 25 25 25 25
594.52 0.113 600.71 0.125 598.06' 0.039 593.85 o.aea 592.21 0.158 598.08* -0.093 597.65 0.227 593.07 0.126 611.47 0.124 615.66 0.057 614.62 -0.012 610.39 -0.017
35 35 35 35 35
056.40 060.78 660.33 055.66 038.18
l40,14 + 131,13 34/2(31/Z) 32/2(31/2) + 30/2(31/Z) * 26/2(31/2) + 32/2(29/2) + 30/2(29/Z) + 26/2(29/a) . 26/2(29/2) f 30/2(27/2) + 29/2(27/z) + 20/2(27/2) + 24/2(27/Z) +
* B
Not
32/2(29/2) 30(2(29/2) 28/2(29/Z) 26/2(29/2) 30/2(27/Z) 26/2(27/Z) 26/2(27/Z) 24/2(27/Z) 26/2(25/2) a6/2(25/2) 24/9(25/Z) 22/2(25/2)
resolved. A = obs. - talc.
35 35 35 35
611.61 616.09 615.58 611.14
-0.103 -0.061 -0.049 -0.065
-0.079 -0.161 -0.087 -0.134 -0.110
35 596.53* -0.103 36 593.58 -0.170 35 037.57 -0.136 35 597.09 -0.110 35 596.534 -0.137 35 592.22 -0.075
vq BAND OF BROMOCHLOROMETHANE
109
TABLE IV-Continued Transition F(
Fl)+
140,14
F'(
79rw35Cl ohs.
Fl')
species B
8h35Cl ohs.
sptx.ies &
* 131,13
a8/2(25/2)
f 26/2(13/Z)
36 615.32
-0.022
35 059.46
-0.071
26/2(25/Z)
+ 24/2(23/2)
35 619.73
-0.027
35 063.84
-0.125
24/2(25/Z)
+ 22/2(23/Z)
35 618.93
-0.177
35 063.20
-0.114
22/2(25/2)
* 20/2(23/2)
35 615.62
-0.064
35 058.74
-0.129
51,4
*
50,5
16/2(13/2)
* 16/2(13/Z)
28 215.96
-0.038
28 194.85
-0.109
14/2(13/2)
* 14/2(13/2)
28 222.11
0.000
28 201.08
-0.050
12/2(13/2)
+ 12/2(13/Z)
28 220.83
0.070
10/2(13/2)
f 10/2(13/2)
28 214.56
-0.163
28 193.65
-0.036
14/2(11/2)
* 14/2(11/2)
28 176.13'
-0.142
28 162.00
-0.031
12/2(11/2)
+ 12/2(11/2)
28 181.70
0.059
28 167.43
0.088
10/2(11/2)
* 10/2(11/Z)
28 180.26
-0.124
28 165.98
-0.163
+
28 174.61
-0.053
28 160.34
-0.052
28 172.19
-0.027
28 177.47
-0.102
8/2(11/Z)
S/2(11/2)
12/2(
9/2)
+ 12/2(
9/2)
10/2(
9/2)
+ 10/2(
9/Z)
28
193.96
-0.028
8/2(
S/2)
c
8/2(
9/2)
28 192.44
0.030
6/2(
S/2)
.. 6/2(
9/2)
10/2(
7/2)
* 10/2(
7/2)
28 226.55
-0.083
28 176.13*
0.086
28 170.12
0.101
28 203.96
-0.107 -0.139
8/2(
712)
+
8/2(
712)
28 232.69
-0.014
28 209.98
6/2(
712)
c
6/2(
712)
28 230.40
0.085
28 207.76
0.016
4/2(
712)
+
4/2(
712)
28 224.19
0.059
28 201.51
-0.046
20/2(17/2)
* 20/2(17/2)
28 994.62
0.029
18/2(17/2)
+ 18/2(17/2)
29 000.21
-0.069
16/2(17/2)
+ 16/2(17/2)
29 033.28
-0.048
28 999.62
-0.116
14/2(17/2)
. 14/2(17/2)
29 026.69
-0.029
28 992.69
-0.027
M/2(15/2)
+ 18/2(15/2)
28 982.54
-0.109
28 950.82
-0.028
16/2(15/2)
+ 16/2(X1/2)
28 989.16
-0.014
28 957.66
-0.019
14/2(15/a)
* 14/2(15/2)
28 988.21
-0.005
28 956.78
-0.069
12/2(15/2)
+ 12/2(15/2)
26 980.77
-0.107
28 948.64
0.052
16/2(13/2)
* 16/2(13/Z)
28 999.22
0.087
14/2(X3/2)
+ 14/2(13/2)
29 003.53
-0.042
28 973.498
0.096
12/2(13/2)
.- 12/2(13/2)
29 002.92
-0.044
28 973.49*
-0.109
10/2(13/2)
* 10/2(13/2)
28 997.41
0.100
28 967.62
-0.015
14/2(11/2)
. 14/2(11/Z)
29 016.46
-0.103
12/2(11/2)
* 12/2(11/2)
29 019.50
0.055
10/2(11/2)
* 10/2(11/2)
29 019.12
0.106
e/2(11/2)
*
8/2(11/2)
29 015.02
-0.155
'1.8
+
So,9
24/2(21/2)
+ 24/2(21/Z)
30 121.26
0.005
30 069.18
0.056
22/2(21/2)
+ 22/2(21/2)
30 127.61
0.077
30 075.43
0.025
20/2(21/Z)
+ 20/2(21/2)
30 126.69
0.034
30.074.52
-0.006
18/2(21/2)
f 18/2(21/Z)
30 120.37
-0.025
30 068.24
-0.025
22/2(19/2)
* 22/2(19/Z)
30 086.87
0.026
30 040.51
-0.010
20/2(19/2)
+ 20/2(19/Z)
30 092.80
0.177
30 046.24
0.099
18/2(19/2)
* 18/2(19/2)
30 092.12
0.143
30 045.77
0.120
16/2(19/2)
+ M/2(19/2)
30 085.88
0.064
30 039.51
0.030
20/2(17/2)
* 20/2(17/Z)
30 092.53
0.027
30 045.54
0.036
18/2(17/2)
f 18/2(17/Z)
30 098.07
-0.021
30 651.01
0.073
NUDE, TANAKA,
110
AND OHKOSHI
TABLE IV-Continued Transition F(F1)+
%,a*
F'( Fl')
'gBr35C1 swcies d ohs.
'lBr3%1 6wcies obs. b
go.9
n3/2ti7fa)+ iefa(i7fa)
so 097.16
14/2(17/Z) + 18/2(15/Z) + 16/2(15/Z) + 14/2(15/2) + 12/2(15/2) +
30 30 30 30 30
091.28 126.23 132.29 131.16 125.14
-0.061 0.113 0.006 0.007 0.017 0.114
30 30 30 30 30 30
050.04 -0.032 043.89 -0.110 073.43 0.046 079.49 0.041 078.32 0.009 072.21 0.033
31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31
510.16 516.60 515.87 509.41 475.92 481.86 461.28 475.01 481.14 486.86 486.12 479.91 514.78 521.08 520.04 513.77
0.017 0.063 0.087 -0.003 0.037 0.108 -0.056 -0.014 0.061 0.016 0.026 0.076 0.078 0.102 -0.005 0.036
31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31
433.95 -0.001 440.39 0.043 439.63 0.029 433.24 0.017 405.53 0.054 411.03* -0,010 411.03' 0.102 404.66 0.050 410.11 -0.057 415.64 0.013 414.85 -0.039 408.64 0.028 437.84 0.046 444.13 0.060 443.12 -0.019 436.80 -0.018
33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33
219.04 -0.008 225.62 -0.004 224.96 0.000 218.39 -0.005 184.14 -0.083 190.04* -0.084 190.04* 0.053 183.45 -0.016 188.86 -0.007 194.67 -0.028 194.06 0.029 187.53 -0.010 222.87 0.019 229.42 0.074 228.56 0.020 221.98 -0.036
33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33
112.54 0.016 119.12 0.022 118.44 0.007 111.85 -0.023 083.56 -0.035 091.31 0.019 089.33 -0.025 082.82 -0.013 085.73 -0.015 093.37 -0.002 092.69 -0.023 086.26 0.047 115.76 0.030 122.26 0.036 121.52 0.099 114.89 -0.002
34 34 34 34 34 34 34 34
201.78 -0.087 208.47 -0.090 207.87 -0.056 201.18 -0.061 166.54 -0.058 172.36* -0.063 172.36* -0.158 165.83 -0.047
33 33 33 33 33 33 33 33
112.54 119.12 118.44 111.85 063.56 091.31 089.33 082.82
14/2(17/Z) 18/2(15/Z) M/2(15/2) 14/2(15/2) 12/2(15/Z)
111.10 + 110,ll 28/2(25/2) + 26/2(25/2) + 24/2(25/2) + 22/2(25/2) + 26/2(23/2) + 24/2(23/2) + 22/2(23/2) + 20/2(23/2) + 24/2(21/2) + 22/2(21/2) + 20/2(21/2) + M/2(21/2) + 22/2(19/2) + 20/2(19/2) + 18/2(19/Z) + E/2(19/2) +
28/2(25/2) 26/2(25/2) 24/2(25/2) 22/2(25/2) 26/2(23/2) 24/2(23/Z) 22/2(23/2) 20/2(23/2) 24/2(21/2) 22/2(21/2) 20/2(21/2) M/2(21/2) 22/2(19/2) 20/2(19/2) 18/2(19/Z) M/2(19/2)
131,12 + 130.13 32/2(29/2) + 30/2(29/2) + 28/2(29/Z) + 26/2(29/2) + 30/2(27/2) + 28/2(27/2) + 26/2(27/2) + 24/2(27/2) + 28/2(25/2) + 26/2(25/2) + 24/2(25/2) + 22/2(25/2) + 26/2(23/2) + 24/2(23/2) + 22/2(23/2) + 20/2(23/2) +
32/2(29/2) 30/2(29/Z) 29/2(29/2) 26/2(29/2) 30/2(27/2) 28/2(27/2) 26/2(27/2) 24/2(27/Z) 28/2(25/2) 26/2(25/2) 24/2(25/2) 22/2(25/2) 26/2(23/2) 24/2(23/2) 22/2(23/2) 20/2(23/z)
141,13 + 140,14 34/2(31/2) + 32/2(31/2) + 30/2(3112) + 28f2(3112) + 32/2(29/2) + 30/2(29/2) + 28/2(29/Z) + 26/2(29/Z) +
34/2(31/2) 32/2(31/2) 30/2(31/2) 28/2(X/2) 32/2(29/2) 30/2(29/2) 28/2(29/2) 26/2(29/Z,
-0.077 -0.157 -0.150 -0.091 -0.034 -0.054 -0.046 -0.046
vq BAND
111
OF BROMOCHLOROMETHANE TABLE IV-Continued 7gBr35C1
Transition F(
F1)
*
141.13
F'(
0bS.
Fl')
%r35Cl
species
A
ohs .
species
*
+ l40,14
30/2(27/Z)
+ 30/2(27/Z)
34 171.12
-0.057
33 085.75
-0.037
28/2(27/2)
+ 28/2(27/2)
34 176.79
-0.149
33 093.37
-0.074
26/2(27/2)
+ 26/2(27/2)
34 176.25
-0.053
33 092.69
-0.093
24/2(27/2)
+ 24/2(27/2)
34 169.64
-0.049
33 086.26
-0.143
28/2(25/2)
+ 28/2(25/2)
34 205.28
-0.062
33 115.76
-0.054
26/2(25/2)
+ 26/2(25/2)
34 211.91
-0.043
33 122.26
-0.112
24/2(25/2)
+ 24/2(25/2)
34 211.13
-0.065
33 121.52
0.007
22/2(25/Z)
+ 22/2(25/2)
34 204.47
-0.086
33 114.89
-0.052
energy difference between the ground and the excited state. The number of transitions used was six: 51,4f 50,5, & f 60,6, 7l,6 + 70,7, g1,7+ go,8, 91,s f 90,9, and 10~ f 10o,ro. Each of the spectra to be measured had to be isolated since overlapping spectra cannot be used in relative intensity measurements. The absorption cell was cooled by refrigeration to keep a constant temperature of -70°C throughout the measurements. The average value of the intensity ratio is 0.200 for the excited state to the ground state. This ratio leads to a vibrational energy difference of 220 cm-‘. The spectra of bromochloromethane are so close and crowded that the measured intensity of a line is naturally affected by other lines. The uncertain results from intensity measurements are due mainly to the weakness and distorted Iineshapes of the observed spectra. In addition, the splittings of the b-type Q-branch transitions are large, and two corresponding tines for the ground and excited vibrational state he a few hundred megacycles apart from each other. The intensity measurements of the spectra of the b-type Q-
300
200
250
150
cm-1 FIG.
1.Raman spectrum of bromochloromethane
in gas phase.
NIIDE, TANAKA, AND OHKOSHI
112
branch transitions could not be performed, and so the total uncertainty will exceed 20%. The u4 band frequency of bromochloromethane in the gas phase was determined to be 224.3 cm-’ by Raman spectroscopy (Fig. 1). The uncertainty was estimated to be k0.2 cm-‘. The derived vibrational energy difference in the microwave study is 220 cm-‘. This assignment performed by microwave spectroscopy is considered to be in agreement with that made by Raman spectroscopy.
TABLE V Nuclear Quadrupole Coupling Constant Tensor of Bromochloromethane in the Inertial System and the Principal System in the Excited Vibrational State 79
Br35 Cl species
*1Br35C1 species
x,, (WZ)
386.09(61) 8
322.?6(63)
Xbb (WZ)
-77.44(50)
-65.10(35)
xc, (mz)
-306.65(95)
-257.66(72)
IX,bI(W xzz (YAz)
370.92(60)
312.43(79)
591.70
496.57
XYY (mz)
-309.65
-257.66
x,, (mz)
-263.05
-236.89
25.60
16.79
Ab UC d % 7gBr/61Br e
0.04326
0.03763
0.59665
0.59662 1.1916
Chlorine x,, (Wz)
-35.32(59)
-35.62(43)
Xbb (UMZ)
-4.94(32)
-4.93(24)
Xcc (az)
40.26(67)
40.45(49)
Ixabl(w x,, (Iwz)
51.7(22)
54.6(15)
-74.01
-76.95
XYY (MZ)
40.26
40.45
xix (wlz)
33.75
36.50
A
-6.51
-3.95
0.08796
0.05133
1.27972
1.27119
Figures in parentheses indicate the uncertainties attached to the last significant figures calculated from 2.5 times the standard deviation. A = x,, - xYY' n = (x,, - XYY)/X,,. ?I = (Xbb - xoc)lx,,. The reported ratio of the quadrupole moments 7gBr and 9lBr nuclei is 1.19707.
“4 BAND OF BROMOCHLOROMETHANE
113
DISCUSSION
In the present microwave study, the rotational transitions of bromochloromethane in the excited vibrational states for both 79Br35C1and 8LBr35C1species have been measured and relative intensity measurements have also been carried out. According to the results of Wagner (4), the v4 vibrational frequency of bromochloromethane was determined to be 227 cm-‘. The vibrational energy difference and frequencies of 220 and 224.3 cm-’ of bromochloromethane in the gas phase determined by microwave and Raman spectroscopy in this study agree well with 227 cm-’ value. We therefore conclude that the excited vibrational state transitions observed and analyzed are probably due to the Br-C-Cl bending vibration of the present molecule. As for the elements of the x tensor in the excited vibrational state, the values in the principal axes system of the quadrupole coupling tensor are obtained by diagonalizing the quadrupole coupling tensor in the principal inertial system. The characteristic values of the x tensor x,, x,, and X,, of 79Br and *‘Br nuclei for the 79Br35C1and B’Br35Clspecies, and x,, X,, and X, of the 35Clnucleus for the “Br3’Cl and 8’Br35Cl species are also given in Table V. The values of the nuclear quadrupole coupling constant tensor in the principal inertial system and principal axes system have nearly the same values as those of the ground state. The electronic structure of the present molecule surrounding the chlorine and bromine nuclei in the excited vibrational state is considered to be unchanged from that of the ground state in spite of the existence of the Br-C-Cl bending vibration. The n value is similar to that in the ground state and indicates that there is no significant deviation from cylindrical symmetry. ACKNOWLEDGMENT
Calculations were carried out at the Computer Center of the National Defense Academy, Japan. RECEIVED:
March 24, 1989 REFERENCES
I. OHKOSHI, J. Mol. Spectrosc., in press. Spectra and Molecular Structure. II. Infrared and Raman Spectra of Polyatomic Molecules,” Van Nostrand, Princeton, NJ, 1945. W. BACHER AND J. WAGNER, 2. Phys. Gem. A&. B43, 191-197 (1939). J. WAGNER, Z. Phys. Chem. Abt. B 45,69-91 (1939). G. EMSCHWILLERAND J. LECOMTE, J. Phys. Les Ulis Fr. 8, 130-144 ( 1937). Y. NIIDE AND I. OHKOSHI, J. Mol. Spectrosc. 128,88-97 ( 1988). A. S. ESBITTAND E. B. WILSON, JR., Rev. Sci. Instrum. 34,901-907 (1963).
I. Y. 2. G. 3. 4. 5. 6. 7.
NUDE AND
HERZBERG, “Molecular