- Email: [email protected]
New bands in the ND c1Π-a1Δ system: spectroscopic constants of the a1Δ state
CIlE\IlC.\L PIIYSICS LIITIIRS
I_ Introduction
hide from its mtrinsic interest as d first-row hydride, the MI radlcd h.~s long been observed in the combustion of nitrogen containing fuels and more recently become of import m understanding the photochemistry ofmnlmoniacal p1.metax-y atmospheres and interstellar chemistry [I ]_ For these reasons the production. kinetics and spectroscopy of the ground and excited states of this molecular species have received on-going attention [2-S] _ In particular, collisional and radiative rekxdtion of the metastabie b t S+ state of NH and ND in u = 0 (the only vibrational level obsened to radiate) has been studied with a variety of atomic and molecular collision partners [g-16] _ The most striking feature of these studies is the large isotope effect for electronic quenching of NH and ND, monitored by observation of the forbidden b ‘c--X 3C- (0,O) emission near 471 nm. Ratios of quenching rates for b tZ+ (NH/ND) > 25 have been measured for Ar as quencher and this ratio exceeds 10 for He and for Kz [ 13]_ Inelastic, rather than reactive quenching must be involved in these cases. Since the
1 cktobrr
1979
b t \‘+ state is nested in the d t1 state_ it is reasonable to h) pothesize that the 1.~~1 isotope effects are due to near resonance of b IS* (u =0) with ro-wbronic levels in the d 1A state in NH with less favourable level matching in ND. This may result in differing effkiencies for collisionally induced non-radiative transfer from b lx+ for the two isotopic species_ To test this conjecture, it is necessary to calculate the energy of higher ro-viburonic levels in 3 lA_ However, the vibrational constants reported for the a 1A state differ considerably among various sources * due to insufficient knowledge of vibrational levels IJ > l_ In this letter. we report high resolution spectra of the newly observed ND c III-3 IA (0,2) and (1,2) bands. and evaluation of spectroscopic constants for the a ‘4 state. Origins of these bands in NH -and ND have been independently observed and reported in a conference abstract [20]. In our previous photoelectric ob* we = 3314 cm-l, w,+, = 63 cm-l
from ref. [ 171; we= 3303
cm-l. w,r,=55cm-‘[1S];we=3231cm-‘.w,re=9S.5 0-t [19]_ 287
I October
1979
1. Experimental w R _z-_ --+-_----_~__,
3595
Dischzrgcs etnissio!! w;ts photogrcpl!ed with &xl& SA-I t%n on 3 S-4 III Ebert spccrrogmph (Jar&--Xsh) in 10th order (300 ii:ie$nim h;lving ;) rhcoretical resolving power of55SOOO and a measured reciprocal tinear dispersion of023 @mm nt 365 ILL Slits were 4Opm_ Overkpping orders were eliminsted via inrrrferencxzfilters wirh maximam rransmission of 20% Ambient rempemture was maintained at 20 + 0S”C for ty piczd exposure times of S 11.A iow pressure mercury kmp and argon Iines in the discharge its&-provided calibration Ities_
3_ Results
and discussion
i\licrodensitometcr traces of the NDc ‘n-a ‘AtO, 2) and (I _2) bands are shown in figs- 1 and 2 respectivelyThe anomalously weak R brznch. an early-noted chttrac-
Fg_ I_ Microde!!sitometer trxe of the (0.2) band of ND c!r~a ‘A_ The R branch is too weak to obseme md is not included in the f~ure. 288
__
__
._-_
--.-
. ____*_--_-
_
I’
z__,
3593
359s
36%7
3505
_ -. -:
-.._
3G,D
. . -
.---L--L_
ZFz
teristic tkature of this b.md system (311. may be due to ;Lqumtu~n interference effect [221 .md was not used in the crticulatioii of spectroscopic constants for the ;L*A %ltc‘.
Air \raeelengths for the fourteen P and Q branch lines oft~~ch bmd \tere convcrrcd to vxuum wakenumbers using Edkn’s formuL [ZS] _These wavenumbcrs are give!1 in colul!!n 3. of tlbie I _ In cohmln 3 arc :ine positions alculated from constants generated using the iterative non-Iiuear fitting procedure ofZare et _d_ [Xl _ This program compares the measured line position wizh those mlcuhted front a numerically diagona!ised mode! fismiltorlirtn with adjustable molecuhr constdnts- L-unbd;t doubling in the III state wx incompieteIy resolved and was ignored_ The iast cohnnn in tabIe 1 is the difference in wavenumbers bettveen the obstned line positions (corrected to vxuum) and the best-fit values for these lines- The sum of squares of the deviations, after regression, and the-estimator of the variance for the (0.2) band xc 0.0533 .md 000385 respectively- For the (I,?) band, they are 0.0253 and 0.00130. The unit is (wavenumber)2_ Rotational const-mts for the lower a lA state are given in table 2. The calculation employs a threeparameter fit and uses fLved v&es of the B and D constants determined from the c i lI state from the high resohition studies of the d IS+-c In system of ND by Graham and Lew [61_ Rotational line positions are defmed by the relation: v=(TL-s;
T,“)+(G;[J”[J”+
G;) + 8; [J’(J’+
1) - (A”)?]
1) - (A’)‘]
\‘olume 66. number 1
ClIEM!CAL
PHYSICS
Table I Rot&mn.d (5
xII-.I
.md (1.2)
bads
‘2%)
-_--
b.md Icm-’
11789 094_ 10 21 I.29
P(5) P(6)
PC)
C.da&trd hnc positron J)
Dit ferencr:
26 1 SO.73 161.21 110.28
0 018 0.011 -0.06 1
_ ~.xcuum)
26180.75 161.2’7 110.22
l’(2) P(j) PC-r)
of ND
__---
Obwr\ed line position __ _ .
Idcntitr
(0.2)
line posrtrons for the to.21
117.95 09-l 22 211.25
-0.062 -0.120 0 045
Q(3)
206.96
206 94
0.018
Qc-0 QW
201.20 i 9x99
201-19 193.98 185.29 175.11 163-A” 150.19 135.39
0010 0.012
Q(6) Q(7)
185.27 175.20
Q(S)
163.55 150.14 135.37
Q(9) Q( 10) (I.
2) band
(cm-’
Q(4) QW Q(6) Q(7) Qts)
QW QUO,
021
O-088 0.132 -0.047 -0
022
, ~xuurn)
2760 1.37 779.97 756.14 730.04 701.61 829.93 822.80
P(1) P(3) P(4) P(5) P(6) Q(2) Q(3)
-0
27801.33
0.042
779.93 756.18 730.07 70 1.60 82995 822.82
-0 010 -0.039 -0 031 0.013 -0.015 -0.015
813.2s
813.79
-0.007
801.37 786.92 770.02 750.75 728.88 704.22 ---
80 1.34 786.95 770.08 750-7 1 728.79 70-t-28
0.03 1 -0.028 -0.063 0.040 0.090 -0.05s
-
3) See text.
(0.2) band v,,? = 26215_53
B’ B” D’ D”
7.6318
bands of
V“US = (7-i - T;)
2 0.08
frozen b)
8.344 f 0 004 6.07 x IO4 frozenb) (4.83 c O-40) x 104
7-158
* 0 05
frozen b)
8.340 IO.003 6.49 x 10~ frozenb) (4.43 * 027) x 10-1
a) Indicated error is two standard deviations_ b)Ref_ [6j_
+ (G; - GE) - &(A’)1
f B;(I\“)~
_
Observations ofb,mds terminating at IJ”= 2 of the .I IA state permits calculation of Bz. al_ wz and a,~: using a multilinear regression treatment of our date (By. vo2. v12) and the datd of Hanson et al. 1251 These spectroscopic constants (n&+J~.‘Oo_Vo,.“lO)_ are shown in table 3. Morse Frdnck-Condon fxtors and r-centroids for NH and ND c * 11-a tA are given in table 3. A number of‘ these fxtors differ significnntly from those of Suchsrd [26] _ We believe that ours are more rehble smce previous caicul~tions rely upon uncertain values of the vibrational frequency md the vibrstioml anharnlonicity of the J IL state. Increasing the number of steps Table 3 Fxcrroxopic cor~srsnrs for ND 3 ‘A irr cm-’ -___- ~-__---_ --.-I__--(17.94) we-_- ‘435.15 WeYe = 39.3s (592) _--.--___-__-
9)
Be= 8.9564 ae = 0.2454
_______
‘) Numbers in parentheses arc 90% confidence
(0.0882) (0.0516)
-
Iexels.
Table -Z Fr.mcb-Condon C’II-Zl’A ____-
---
_ L!
_ =o
-___
factors (top) and r-centroids _
_.-
--
___
___--__-
“‘.Z
--
(bottom)
for
--_~
1
3
US’ =
u” = 2
- ___---_
NH a) u’= 0
0.7128 1.097
0.2561 I-256
0 2826 1.460
u’= 1
0.19G3 0.9851
o-2205 l-161
0.4249 1.296
“’ = 2
0 5340 0.9061
(-1)
0.2119
0.2167 l-SO7
(-3)
1.070
0.1794
(-1)
O-1077
0.5392
(-1)
0.2685 1530
(-1)
(-2)
(x1349 1.471 0.2943 1.347 0.1077
0.8568
1.006
1.180
O-7217
0.2293 1.221
0.4351
1.080
I.317
0.5202 I.423
0.2274
0.2845
0.3344
0.1258
0 9817
1.106
1.249
0.3206 1023
0.4280 l-107
:
1.266
ND u’ = 0
(1.2) band rJt2 = 27837.05
1979
and the b.md origins are defined by:
J = 3 Table 2 Spectroscopic constants for the (0.2) and (1,2) ND(c’iI-a ‘a). All ~Iues are in cm-’ a)
1 October
LETTERS
U’ = 1 v* =2
0.4366 0.8709
(-1)
v’ = 3
0.6443 0.7325
(-2)
(-1)
(-2)
I.343 (--I)
0.2954 1280
0.1250
0.2598
O-721 1 (-2)
0.9305
1061
1.324
‘) we\r;: from ref. [28!.0_2826
(-1)
equals
0.2826
x
IO-‘_
289
hi the irricgr-lfi~~u lkwl
50 t0 100
*ri t!tc \Ihr~ti~~t?JlrBitr~l~~~
step rw&
3 ric$gbtc
irrrcgrals
dit t>rr’ucc
fu
ixtw%_ It is interr~ting to ncae thxf Ztxrrch [ZOl rc’purts lx&?; ori+uin~ ir0n: u’ = 1 ‘11the 5 111st;Ltr:d \D 111~ Frmlck-
(‘ou&~
hut &rsb not report St1 x13
.SI> hare
bauds above
u’ = I tbr AI Z. Siucc
c~~u~t:~r;lble Frauch
-C‘~rurlw~ txtors
tilr the (1-O) and t3_ I ) bartd~ either axrgrtic> of thr production inc&;lnLtu c*r prr’dt5s0..xk~trftol the c‘ t II star lpcrh~ps by tlw 5\- strltc) is nxticrttc2d.1 here Is ar,rG.ier_tbk &datc1-\ r-t &IS latter prwcss \‘71_ ~lzanst and ct,-aorhcr> hare pointed out [?I that the JcnGty ofst.ttr\ of S 3x- 2nd ;1t1 iuto which rel~xaiun ofu = 0 of b I\-* sould occur is greater rn SD thrtn in NL Thus the probabihty of near a>irlsidcnca (= 0.25 x-l’) bcrr\een le\eIs of the b ‘Y+ >t.tte aid of ths ;L II or .Y 3’-4 stdti’s ia Ilighcr iii Ir;t) tkui ill X11_ Sotk%it&5s_ it i I\lt iht rrpptirz ro r‘~flhlt mush I-Lstrr phyk11 quenching. ii-c must aget with rhis conclusion_ Ottr krcl cxkttLtion5 indicate that no convinciug prcdoniin;lnct of slosc pairs in the b i ‘* sr.rtr’rrttdthr 3 ‘1 st.ttc occurs in sithsr XI I or SD_ Scvcral :w.tr rcson;Incc~ occur in Si I (C -> I*_b t\‘*(u=fl_J=-L):~ lJ.(v=l_J= 13) \\ith III= 1-G cm- ' ) but other &SC pairs oc‘cur in SD (e-g_ bt\‘*(u=0_1~?);s~-l(u=-f_f =f)~r_ith~f~=5_3 cn1- 1 IIt therckrc stems to US tImI aiWtilcr rs.\phllatiwl Tar thtic vastly diffcrcnt qucnchin~ rates must bc sought_ It does not stem likely that rotation&y dcpendent, non-radiatiw couplin,= analogous to the rotational Perturbation A ‘11-B 2-t occurring in CtS. ;1ssuggcstcd by Blasanct et ai_ is rckvant to the observed isoropc effects_ Pcrtttrbations between the ncstcd b. ;I, and X stais of NH (and ND) are. tmiikc thc_CS intcrrtction, forbidden and in fact arc not obscncd. In addition. ‘0 1?-a la orb 1S*-X3Tenergy transfer hzs much ices favorable Fanck-Condon factors for b ‘?(u=O) rchxation than dots A’lI(uv= IO)B’?(a=O) in CN_ FinaLiy_ a wezk perturbation between bound states is unlikely to affect a coZsiona1 rcktxation process_ In the case of NH (unlike CN) it is also uniikcly to increase the spontaneous radiation rate_ We believe therefore that the explanation for the striking difference in quenching rates, kKH S- kNDF is not to be found in properties of the isohtcd molecuks NH and ND, but requires a more detailed understanding of the interaction between excited molecule and quencher_ 290
References
141 I-. Albarr .md E-X. Dou~tz._Chem_ Ph),. 3J f 19781 399. I.5 1 A P- Bzron\:aki. R.G. Hitler zmd J.R. .\tcDun.~td_Chem. Ph)S 30 f 1976) 119.133. 16 j K’_R.Y_ G&%&m and If. LIZ\\ _&n. J. Ph\s- 56 f 1976155. 17 j A. ttxrtford Jr.. Chsm. t’h)a. Letters 57 f 1978) 352. iS1 I). Geternt .md A L. Smith.Chem. Ph>s. Lclrcrb 60 f 1979) 261. 19 1 A. Gllkb. J. Mwncr axi C. Vermcil. Chcm. Ph) 3. Lctrerl I.5 (197J) 346. [ 101 J U~xmcl. A. G11ks and C. Vermert. J. Photurhem. 3 0975)417. [ 1 I 1 II. Gekmt. S-V. F&%h .md T_ C.wrngron. Chem. Ph) J. Lctfers 36 (1975) 238. [ 12 J C. Zetrs& and I=_Srnht. Chem. Ph_\z._Letter, 33 f 1975) 375113 1 B. Celernr. S-V_ I‘xLwclr znd T_ Caringon. J. Chem. Ph_r5. 65 (1976) I I. ltlj C_Zetrs,h and F.StuhL J_Chem. Ph!,- 66 (1976) 3107[ I5 1 C_ Zetnch axd F. StuhL Bcr. Bumcnges. PI1 siti. Chrm_ 80 (1976) 135-t_ [ 161 C. Zetzxh. Ber. Bunsen~_es_Ph) sk Chem. 63 (1978) 1098. [I?.’ J-31. Lctnts. J. Qtunt. Specrr>_ Radiatiw Transfer 13 (1973) 297. [ I8 1 L_ Ro&nn. Sslecrcxt consfants and spectroscopic data reiarile to dhtomic molecules (Perrgmon Press. New York. 1970). [ISI hf. Shimauchi_Sci_ Light (Jap.m) 13 (196-Z) 531201 C_Zetzsch, J- Photochem. 9 (1978) 151_ 1211 R.W.B. Pezrrsc. Proc. Rol. Sot. Al43 (1933) 112. 122: A.R. Gortscho. J-B. Koffcnd. R.W. FieId and J.R. Lomb.udi. J_Chrm_ Phrs. 68 (1978) 4110. [23 1 C_K- Allen. Astrophyskd quantities (_Afhtone Press. London. 1963). [24 1 R-N- Zare, A-L_ Schmeltetcopf. W.J. Harrop and D.L. Albritton, J. Mot_ Spectry_ 46 (1973) 37125 1 H. Hanson,1. Kopp. Bl. Kronckvis: and N. Aslund. Arkiv.
Fysik 30 (1964) 1. [26I S.N. Suchard. Spectroscopic
consfanfs for selected heteronuclear ditomic motccules (IFI!Plenum Press. New York. 1975). 127 1 Wm.H. Smith. J. Brzozo~ski and J. Ermzn. J. Chem. Phys. 64 (1976) 4628. 1281 S.N_ Such~d. Spectroscopic constants for selected hetcronuclear diatomic molecules. Vol. 2, Air Force Report No. S_AMSO-TR-74-82 (1974).
I_ Introduction
hide from its mtrinsic interest as d first-row hydride, the MI radlcd h.~s long been observed in the combustion of nitrogen containing fuels and more recently become of import m understanding the photochemistry ofmnlmoniacal p1.metax-y atmospheres and interstellar chemistry [I ]_ For these reasons the production. kinetics and spectroscopy of the ground and excited states of this molecular species have received on-going attention [2-S] _ In particular, collisional and radiative rekxdtion of the metastabie b t S+ state of NH and ND in u = 0 (the only vibrational level obsened to radiate) has been studied with a variety of atomic and molecular collision partners [g-16] _ The most striking feature of these studies is the large isotope effect for electronic quenching of NH and ND, monitored by observation of the forbidden b ‘c--X 3C- (0,O) emission near 471 nm. Ratios of quenching rates for b tZ+ (NH/ND) > 25 have been measured for Ar as quencher and this ratio exceeds 10 for He and for Kz [ 13]_ Inelastic, rather than reactive quenching must be involved in these cases. Since the
1 cktobrr
1979
b t \‘+ state is nested in the d t1 state_ it is reasonable to h) pothesize that the 1.~~1 isotope effects are due to near resonance of b IS* (u =0) with ro-wbronic levels in the d 1A state in NH with less favourable level matching in ND. This may result in differing effkiencies for collisionally induced non-radiative transfer from b lx+ for the two isotopic species_ To test this conjecture, it is necessary to calculate the energy of higher ro-viburonic levels in 3 lA_ However, the vibrational constants reported for the a 1A state differ considerably among various sources * due to insufficient knowledge of vibrational levels IJ > l_ In this letter. we report high resolution spectra of the newly observed ND c III-3 IA (0,2) and (1,2) bands. and evaluation of spectroscopic constants for the a ‘4 state. Origins of these bands in NH -and ND have been independently observed and reported in a conference abstract [20]. In our previous photoelectric ob* we = 3314 cm-l, w,+, = 63 cm-l
from ref. [ 171; we= 3303
cm-l. w,r,=55cm-‘[1S];we=3231cm-‘.w,re=9S.5 0-t [19]_ 287
I October
1979
1. Experimental w R _z-_ --+-_----_~__,
3595
Dischzrgcs etnissio!! w;ts photogrcpl!ed with &xl& SA-I t%n on 3 S-4 III Ebert spccrrogmph (Jar&--Xsh) in 10th order (300 ii:ie$nim h;lving ;) rhcoretical resolving power of55SOOO and a measured reciprocal tinear dispersion of023 @mm nt 365 ILL Slits were 4Opm_ Overkpping orders were eliminsted via inrrrferencxzfilters wirh maximam rransmission of 20% Ambient rempemture was maintained at 20 + 0S”C for ty piczd exposure times of S 11.A iow pressure mercury kmp and argon Iines in the discharge its&-provided calibration Ities_
3_ Results
and discussion
i\licrodensitometcr traces of the NDc ‘n-a ‘AtO, 2) and (I _2) bands are shown in figs- 1 and 2 respectivelyThe anomalously weak R brznch. an early-noted chttrac-
Fg_ I_ Microde!!sitometer trxe of the (0.2) band of ND c!r~a ‘A_ The R branch is too weak to obseme md is not included in the f~ure. 288
__
__
._-_
--.-
. ____*_--_-
_
I’
z__,
3593
359s
36%7
3505
_ -. -:
-.._
3G,D
. . -
.---L--L_
ZFz
teristic tkature of this b.md system (311. may be due to ;Lqumtu~n interference effect [221 .md was not used in the crticulatioii of spectroscopic constants for the ;L*A %ltc‘.
Air \raeelengths for the fourteen P and Q branch lines oft~~ch bmd \tere convcrrcd to vxuum wakenumbers using Edkn’s formuL [ZS] _These wavenumbcrs are give!1 in colul!!n 3. of tlbie I _ In cohmln 3 arc :ine positions alculated from constants generated using the iterative non-Iiuear fitting procedure ofZare et _d_ [Xl _ This program compares the measured line position wizh those mlcuhted front a numerically diagona!ised mode! fismiltorlirtn with adjustable molecuhr constdnts- L-unbd;t doubling in the III state wx incompieteIy resolved and was ignored_ The iast cohnnn in tabIe 1 is the difference in wavenumbers bettveen the obstned line positions (corrected to vxuum) and the best-fit values for these lines- The sum of squares of the deviations, after regression, and the-estimator of the variance for the (0.2) band xc 0.0533 .md 000385 respectively- For the (I,?) band, they are 0.0253 and 0.00130. The unit is (wavenumber)2_ Rotational const-mts for the lower a lA state are given in table 2. The calculation employs a threeparameter fit and uses fLved v&es of the B and D constants determined from the c i lI state from the high resohition studies of the d IS+-c In system of ND by Graham and Lew [61_ Rotational line positions are defmed by the relation: v=(TL-s;
T,“)+(G;[J”[J”+
G;) + 8; [J’(J’+
1) - (A”)?]
1) - (A’)‘]
\‘olume 66. number 1
ClIEM!CAL
PHYSICS
Table I Rot&mn.d (5
xII-.I
.md (1.2)
bads
‘2%)
-_--
b.md Icm-’
11789 094_ 10 21 I.29
P(5) P(6)
PC)
C.da&trd hnc positron J)
Dit ferencr:
26 1 SO.73 161.21 110.28
0 018 0.011 -0.06 1
_ ~.xcuum)
26180.75 161.2’7 110.22
l’(2) P(j) PC-r)
of ND
__---
Obwr\ed line position __ _ .
Idcntitr
(0.2)
line posrtrons for the to.21
117.95 09-l 22 211.25
-0.062 -0.120 0 045
Q(3)
206.96
206 94
0.018
Qc-0 QW
201.20 i 9x99
201-19 193.98 185.29 175.11 163-A” 150.19 135.39
0010 0.012
Q(6) Q(7)
185.27 175.20
Q(S)
163.55 150.14 135.37
Q(9) Q( 10) (I.
2) band
(cm-’
Q(4) QW Q(6) Q(7) Qts)
QW QUO,
021
O-088 0.132 -0.047 -0
022
, ~xuurn)
2760 1.37 779.97 756.14 730.04 701.61 829.93 822.80
P(1) P(3) P(4) P(5) P(6) Q(2) Q(3)
-0
27801.33
0.042
779.93 756.18 730.07 70 1.60 82995 822.82
-0 010 -0.039 -0 031 0.013 -0.015 -0.015
813.2s
813.79
-0.007
801.37 786.92 770.02 750.75 728.88 704.22 ---
80 1.34 786.95 770.08 750-7 1 728.79 70-t-28
0.03 1 -0.028 -0.063 0.040 0.090 -0.05s
-
3) See text.
(0.2) band v,,? = 26215_53
B’ B” D’ D”
7.6318
bands of
V“US = (7-i - T;)
2 0.08
frozen b)
8.344 f 0 004 6.07 x IO4 frozenb) (4.83 c O-40) x 104
7-158
* 0 05
frozen b)
8.340 IO.003 6.49 x 10~ frozenb) (4.43 * 027) x 10-1
a) Indicated error is two standard deviations_ b)Ref_ [6j_
+ (G; - GE) - &(A’)1
f B;(I\“)~
_
Observations ofb,mds terminating at IJ”= 2 of the .I IA state permits calculation of Bz. al_ wz and a,~: using a multilinear regression treatment of our date (By. vo2. v12) and the datd of Hanson et al. 1251 These spectroscopic constants (n&+J~.‘Oo_Vo,.“lO)_ are shown in table 3. Morse Frdnck-Condon fxtors and r-centroids for NH and ND c * 11-a tA are given in table 3. A number of‘ these fxtors differ significnntly from those of Suchsrd [26] _ We believe that ours are more rehble smce previous caicul~tions rely upon uncertain values of the vibrational frequency md the vibrstioml anharnlonicity of the J IL state. Increasing the number of steps Table 3 Fxcrroxopic cor~srsnrs for ND 3 ‘A irr cm-’ -___- ~-__---_ --.-I__--(17.94) we-_- ‘435.15 WeYe = 39.3s (592) _--.--___-__-
9)
Be= 8.9564 ae = 0.2454
_______
‘) Numbers in parentheses arc 90% confidence
(0.0882) (0.0516)
-
Iexels.
Table -Z Fr.mcb-Condon C’II-Zl’A ____-
---
_ L!
_ =o
-___
factors (top) and r-centroids _
_.-
--
___
___--__-
“‘.Z
--
(bottom)
for
--_~
1
3
US’ =
u” = 2
- ___---_
NH a) u’= 0
0.7128 1.097
0.2561 I-256
0 2826 1.460
u’= 1
0.19G3 0.9851
o-2205 l-161
0.4249 1.296
“’ = 2
0 5340 0.9061
(-1)
0.2119
0.2167 l-SO7
(-3)
1.070
0.1794
(-1)
O-1077
0.5392
(-1)
0.2685 1530
(-1)
(-2)
(x1349 1.471 0.2943 1.347 0.1077
0.8568
1.006
1.180
O-7217
0.2293 1.221
0.4351
1.080
I.317
0.5202 I.423
0.2274
0.2845
0.3344
0.1258
0 9817
1.106
1.249
0.3206 1023
0.4280 l-107
:
1.266
ND u’ = 0
(1.2) band rJt2 = 27837.05
1979
and the b.md origins are defined by:
J = 3 Table 2 Spectroscopic constants for the (0.2) and (1,2) ND(c’iI-a ‘a). All ~Iues are in cm-’ a)
1 October
LETTERS
U’ = 1 v* =2
0.4366 0.8709
(-1)
v’ = 3
0.6443 0.7325
(-2)
(-1)
(-2)
I.343 (--I)
0.2954 1280
0.1250
0.2598
O-721 1 (-2)
0.9305
1061
1.324
‘) we\r;: from ref. [28!.0_2826
(-1)
equals
0.2826
x
IO-‘_
289
hi the irricgr-lfi~~u lkwl
50 t0 100
*ri t!tc \Ihr~ti~~t?JlrBitr~l~~~
step rw&
3 ric$gbtc
irrrcgrals
dit t>rr’ucc
fu
ixtw%_ It is interr~ting to ncae thxf Ztxrrch [ZOl rc’purts lx&?; ori+uin~ ir0n: u’ = 1 ‘11the 5 111st;Ltr:d \D 111~ Frmlck-
(‘ou&~
hut &rsb not report St1 x13
.SI> hare
bauds above
u’ = I tbr AI Z. Siucc
c~~u~t:~r;lble Frauch
-C‘~rurlw~ txtors
tilr the (1-O) and t3_ I ) bartd~ either axrgrtic> of thr production inc&;lnLtu c*r prr’dt5s0..xk~trftol the c‘ t II star lpcrh~ps by tlw 5\- strltc) is nxticrttc2d.1 here Is ar,rG.ier_tbk &datc1-\ r-t &IS latter prwcss \‘71_ ~lzanst and ct,-aorhcr> hare pointed out [?I that the JcnGty ofst.ttr\ of S 3x- 2nd ;1t1 iuto which rel~xaiun ofu = 0 of b I\-* sould occur is greater rn SD thrtn in NL Thus the probabihty of near a>irlsidcnca (= 0.25 x-l’) bcrr\een le\eIs of the b ‘Y+ >t.tte aid of ths ;L II or .Y 3’-4 stdti’s ia Ilighcr iii Ir;t) tkui ill X11_ Sotk%it&5s_ it i I\lt iht rrpptirz ro r‘~flhlt mush I-Lstrr phyk11 quenching. ii-c must aget with rhis conclusion_ Ottr krcl cxkttLtion5 indicate that no convinciug prcdoniin;lnct of slosc pairs in the b i ‘* sr.rtr’rrttdthr 3 ‘1 st.ttc occurs in sithsr XI I or SD_ Scvcral :w.tr rcson;Incc~ occur in Si I (C -> I*_b t\‘*(u=fl_J=-L):~ lJ.(v=l_J= 13) \\ith III= 1-G cm- ' ) but other &SC pairs oc‘cur in SD (e-g_ bt\‘*(u=0_1~?);s~-l(u=-f_f =f)~r_ith~f~=5_3 cn1- 1 IIt therckrc stems to US tImI aiWtilcr rs.\phllatiwl Tar thtic vastly diffcrcnt qucnchin~ rates must bc sought_ It does not stem likely that rotation&y dcpendent, non-radiatiw couplin,= analogous to the rotational Perturbation A ‘11-B 2-t occurring in CtS. ;1ssuggcstcd by Blasanct et ai_ is rckvant to the observed isoropc effects_ Pcrtttrbations between the ncstcd b. ;I, and X stais of NH (and ND) are. tmiikc thc_CS intcrrtction, forbidden and in fact arc not obscncd. In addition. ‘0 1?-a la orb 1S*-X3Tenergy transfer hzs much ices favorable Fanck-Condon factors for b ‘?(u=O) rchxation than dots A’lI(uv= IO)B’?(a=O) in CN_ FinaLiy_ a wezk perturbation between bound states is unlikely to affect a coZsiona1 rcktxation process_ In the case of NH (unlike CN) it is also uniikcly to increase the spontaneous radiation rate_ We believe therefore that the explanation for the striking difference in quenching rates, kKH S- kNDF is not to be found in properties of the isohtcd molecuks NH and ND, but requires a more detailed understanding of the interaction between excited molecule and quencher_ 290
References
141 I-. Albarr .md E-X. Dou~tz._Chem_ Ph),. 3J f 19781 399. I.5 1 A P- Bzron\:aki. R.G. Hitler zmd J.R. .\tcDun.~td_Chem. Ph)S 30 f 1976) 119.133. 16 j K’_R.Y_ G&%&m and If. LIZ\\ _&n. J. Ph\s- 56 f 1976155. 17 j A. ttxrtford Jr.. Chsm. t’h)a. Letters 57 f 1978) 352. iS1 I). Geternt .md A L. Smith.Chem. Ph>s. Lclrcrb 60 f 1979) 261. 19 1 A. Gllkb. J. Mwncr axi C. Vermcil. Chcm. Ph) 3. Lctrerl I.5 (197J) 346. [ 101 J U~xmcl. A. G11ks and C. Vermert. J. Photurhem. 3 0975)417. [ 1 I 1 II. Gekmt. S-V. F&%h .md T_ C.wrngron. Chem. Ph) J. Lctfers 36 (1975) 238. [ 12 J C. Zetrs& and I=_Srnht. Chem. Ph_\z._Letter, 33 f 1975) 375113 1 B. Celernr. S-V_ I‘xLwclr znd T_ Caringon. J. Chem. Ph_r5. 65 (1976) I I. ltlj C_Zetrs,h and F.StuhL J_Chem. Ph!,- 66 (1976) 3107[ I5 1 C_ Zetnch axd F. StuhL Bcr. Bumcnges. PI1 siti. Chrm_ 80 (1976) 135-t_ [ 161 C. Zetzxh. Ber. Bunsen~_es_Ph) sk Chem. 63 (1978) 1098. [I?.’ J-31. Lctnts. J. Qtunt. Specrr>_ Radiatiw Transfer 13 (1973) 297. [ I8 1 L_ Ro&nn. Sslecrcxt consfants and spectroscopic data reiarile to dhtomic molecules (Perrgmon Press. New York. 1970). [ISI hf. Shimauchi_Sci_ Light (Jap.m) 13 (196-Z) 531201 C_Zetzsch, J- Photochem. 9 (1978) 151_ 1211 R.W.B. Pezrrsc. Proc. Rol. Sot. Al43 (1933) 112. 122: A.R. Gortscho. J-B. Koffcnd. R.W. FieId and J.R. Lomb.udi. J_Chrm_ Phrs. 68 (1978) 4110. [23 1 C_K- Allen. Astrophyskd quantities (_Afhtone Press. London. 1963). [24 1 R-N- Zare, A-L_ Schmeltetcopf. W.J. Harrop and D.L. Albritton, J. Mot_ Spectry_ 46 (1973) 37125 1 H. Hanson,1. Kopp. Bl. Kronckvis: and N. Aslund. Arkiv.
Fysik 30 (1964) 1. [26I S.N. Suchard. Spectroscopic
consfanfs for selected heteronuclear ditomic motccules (IFI!Plenum Press. New York. 1975). 127 1 Wm.H. Smith. J. Brzozo~ski and J. Ermzn. J. Chem. Phys. 64 (1976) 4628. 1281 S.N_ Such~d. Spectroscopic constants for selected hetcronuclear diatomic molecules. Vol. 2, Air Force Report No. S_AMSO-TR-74-82 (1974).