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The vibrational frequencies of HNO
Volime 23, number 2
.’
CHEMICAL PHYSICS LETTERS
.:
15 November 1973
.’ THE VIBRATIONAL
l?RE@JENCl&
OF HNO
P.N. CLOUGH*, B.A. THRUSH Deporrmenr
of Phy+al
Chemistry, Cambridge CB2 IEP. UK
and D.A. RAMSAY and J.G. STAMPER** Divisiori of Physics. Nation21 Research Council
of Car~adu,01raw.
Canada KlA OR6
Received 29 August 1973
Electronic and vibrational emission spectra have been produced by the reaction of H atoms with NO, nnd studied under moderate resolving power. Preliminary rotational analyses of some of the bands give Y’,’= 2684.7 cm-‘, u;’ = different from earlier published values. 1565.3 cm-’ and LJ;’= 1500.4 cm-‘. The values for v’,’and v’; are considerably
The vibrational frequencies for HNO in its ground state have been determined primarily from matrix iso-
lation studies [l-3] . The generally quoted values [4] arevl=3596,u2=1562and~3=1110cm~~,where “I and v2 are the N-H and N = 0 stretching frequencies respectively, and v3 is the bending frequency. More recently, values of u1 = 3450 cm-l [5] and 3300 cm-l [6] have been proposed. No hot bands have been observed in the electronic absorption spectrum [7,8] but vibrational and electronic emission spectra have been observed at low resolution in the reaction of H atoms with NO [9, lo]. We have now studied these emission spectra with higher resolution and carried out preliminary rotational analyses of some of the bands, Bands of the x IA”-x IA’ system were photographed at Ottawa using the first order of a 6.4 m concave grating spectrograph. Rotational analysis of the bands near 11589 and 12636 cm-l indicate that they originate in the 000 and 001 levels of the excited
state respectively. The bands are assigned to the 000-010 and 001-001 transitions, giving P; = 1565.3 cm-l and LJ;’= 1500., cm-l _These levels show interactions with increasing values of K which are being analysed. Measurements at Cambridge on vibrational emission bands from the H + NO reaction were made with the previously described apparatus [ 111. The strongest emission around 3.7 pm consists of a number of line-like features on an unresolved background. The most intense features form a series with the quadratic spacing expected for the Q branches in a perpendicular band of a near-symmetric rotor; a similar weaker series is also observed_ Analyses of these series yield the molecular constants given in table 1. The value of (A”-B”) for the OOOlevel is in good agreement with the value obtained by DaJby [7] from the electronic spectrum, viz., 17.12 cm-l. Moreover the decrease in (14 - E) with increasing u 1 parallels the beTable 1
* Present address: Department of Pure and Applied Physics, Queen% University of Belfast, Northern Ireland. * Present address: School of Molecular Sciences, University of Sussex, Brighton, UK.
Origin -1 (cm )
2684.7 .2665.3
A’-B
A” - p’
(cm-‘)
(cm-’ )
16.1g
17.03 16.1,
15.8,
Identification
100-000 200-100
CHEMICAL PHYSICS LETTERS
Volume 23, number 2
15,November 1973
References
haviour fcund in the excited state [8]. The above work indicates that two of the earlier ~bration~ freque~cies.ofHNO need significant revh sion. The new vrrluc for the N-H stretching frequency is more reasonable in view of the law dissociation energj (48.6 kcal mole -1 [IO] ) and the fact that in the IA” excited state the N-H bond is shorter and the stretching frequency is 2854.2 cm-l [S] . A value of 0; = 2717 cm-l has been reported very recently by O&vie [ 121 for an argon matrix. Both new assign. ments are confirmed by the recent matrizz-isolation studies of Jacox and Milligan [ 131 using six different isotopic species.
[ 11 H.W. Brown and G.C. Pimenlel, J.‘Chcm. Phys 29 (1958) 883. [2]
K,B. Harvcy and H.W. Brovm.3. China. Phys 56 f1959), 745.
[ 3) DE. MiIligan. NE. Jacox, S.W: Charles end G.C. Pimentei, J. Chem, Phys. 37 (1962) 2302. [4] G. Henberg, Eteclronic spectra of poIyutomic molecules (Van Nostrand, Princeton. 1966) p. 589. 151 J.F. Ogilvie, Spectrochim. Act3 23A (1967) 737. [6] GE. McGraw and H.S. Johnston. Intern. 3. Chem. Kinetics 1(1969) 89. [71 F.W. Ddby. Can. J.Phys. 36 (1958) 1336;
[S] J.L. Bancroft, J.M. Hollas and D.A. Ramsey, Can. I. Phys. 40 (1962)
322.
[ 9f J.K. Cashion and J.C. Potanyi. J. Chem. Phys. 30 (1959) 317. [ 101 MJ.Y. Clement and D.A. Ramuy, Can. J. Phys. 39
We thank Drs. D.E. Malign and M.E. Jacox for communjcation of unpublished results. B.A.T. thanks the National Research Council of Canada for a Senior Visiting Fellowship.
(196I)
205.
[ll] P.N. Clough and B.A. Thrush, Proc. Roy. Sot. A309 (1969) 419.
[ 121J.F. O&k, Nature 243 (1973) 210. [ 131 ME. Jacox and D.E. ~~~ii6an, J. Mot. Spectry., to be published.
. .‘.
156
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.;
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.i
.’
CHEMICAL PHYSICS LETTERS
.:
15 November 1973
.’ THE VIBRATIONAL
l?RE@JENCl&
OF HNO
P.N. CLOUGH*, B.A. THRUSH Deporrmenr
of Phy+al
Chemistry, Cambridge CB2 IEP. UK
and D.A. RAMSAY and J.G. STAMPER** Divisiori of Physics. Nation21 Research Council
of Car~adu,01raw.
Canada KlA OR6
Received 29 August 1973
Electronic and vibrational emission spectra have been produced by the reaction of H atoms with NO, nnd studied under moderate resolving power. Preliminary rotational analyses of some of the bands give Y’,’= 2684.7 cm-‘, u;’ = different from earlier published values. 1565.3 cm-’ and LJ;’= 1500.4 cm-‘. The values for v’,’and v’; are considerably
The vibrational frequencies for HNO in its ground state have been determined primarily from matrix iso-
lation studies [l-3] . The generally quoted values [4] arevl=3596,u2=1562and~3=1110cm~~,where “I and v2 are the N-H and N = 0 stretching frequencies respectively, and v3 is the bending frequency. More recently, values of u1 = 3450 cm-l [5] and 3300 cm-l [6] have been proposed. No hot bands have been observed in the electronic absorption spectrum [7,8] but vibrational and electronic emission spectra have been observed at low resolution in the reaction of H atoms with NO [9, lo]. We have now studied these emission spectra with higher resolution and carried out preliminary rotational analyses of some of the bands, Bands of the x IA”-x IA’ system were photographed at Ottawa using the first order of a 6.4 m concave grating spectrograph. Rotational analysis of the bands near 11589 and 12636 cm-l indicate that they originate in the 000 and 001 levels of the excited
state respectively. The bands are assigned to the 000-010 and 001-001 transitions, giving P; = 1565.3 cm-l and LJ;’= 1500., cm-l _These levels show interactions with increasing values of K which are being analysed. Measurements at Cambridge on vibrational emission bands from the H + NO reaction were made with the previously described apparatus [ 111. The strongest emission around 3.7 pm consists of a number of line-like features on an unresolved background. The most intense features form a series with the quadratic spacing expected for the Q branches in a perpendicular band of a near-symmetric rotor; a similar weaker series is also observed_ Analyses of these series yield the molecular constants given in table 1. The value of (A”-B”) for the OOOlevel is in good agreement with the value obtained by DaJby [7] from the electronic spectrum, viz., 17.12 cm-l. Moreover the decrease in (14 - E) with increasing u 1 parallels the beTable 1
* Present address: Department of Pure and Applied Physics, Queen% University of Belfast, Northern Ireland. * Present address: School of Molecular Sciences, University of Sussex, Brighton, UK.
Origin -1 (cm )
2684.7 .2665.3
A’-B
A” - p’
(cm-‘)
(cm-’ )
16.1g
17.03 16.1,
15.8,
Identification
100-000 200-100
CHEMICAL PHYSICS LETTERS
Volume 23, number 2
15,November 1973
References
haviour fcund in the excited state [8]. The above work indicates that two of the earlier ~bration~ freque~cies.ofHNO need significant revh sion. The new vrrluc for the N-H stretching frequency is more reasonable in view of the law dissociation energj (48.6 kcal mole -1 [IO] ) and the fact that in the IA” excited state the N-H bond is shorter and the stretching frequency is 2854.2 cm-l [S] . A value of 0; = 2717 cm-l has been reported very recently by O&vie [ 121 for an argon matrix. Both new assign. ments are confirmed by the recent matrizz-isolation studies of Jacox and Milligan [ 131 using six different isotopic species.
[ 11 H.W. Brown and G.C. Pimenlel, J.‘Chcm. Phys 29 (1958) 883. [2]
K,B. Harvcy and H.W. Brovm.3. China. Phys 56 f1959), 745.
[ 3) DE. MiIligan. NE. Jacox, S.W: Charles end G.C. Pimentei, J. Chem, Phys. 37 (1962) 2302. [4] G. Henberg, Eteclronic spectra of poIyutomic molecules (Van Nostrand, Princeton. 1966) p. 589. 151 J.F. Ogilvie, Spectrochim. Act3 23A (1967) 737. [6] GE. McGraw and H.S. Johnston. Intern. 3. Chem. Kinetics 1(1969) 89. [71 F.W. Ddby. Can. J.Phys. 36 (1958) 1336;
[S] J.L. Bancroft, J.M. Hollas and D.A. Ramsey, Can. I. Phys. 40 (1962)
322.
[ 9f J.K. Cashion and J.C. Potanyi. J. Chem. Phys. 30 (1959) 317. [ 101 MJ.Y. Clement and D.A. Ramuy, Can. J. Phys. 39
We thank Drs. D.E. Malign and M.E. Jacox for communjcation of unpublished results. B.A.T. thanks the National Research Council of Canada for a Senior Visiting Fellowship.
(196I)
205.
[ll] P.N. Clough and B.A. Thrush, Proc. Roy. Sot. A309 (1969) 419.
[ 121J.F. O&k, Nature 243 (1973) 210. [ 131 ME. Jacox and D.E. ~~~ii6an, J. Mot. Spectry., to be published.
. .‘.
156
.‘.I . .’
. . _’
...
:
,.. . :,
: .:)_ _..
.,
,;
,, ;,
.’
..’
.’
.:-
_,
.‘.
.:~ ._ _.
:
.” ,,
.;
,‘.,
‘,
.i