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Vibrational energy pathways in N2O
Speclrochrmictl Acla, Vol. 39A.No. 7. p. 661.1983 Printed m GreatBritam
0584-8539183 S3.M)+ 0.M) Q 1983Pergamon PressLtd.
Vibrational C. Laboratoire
de Photophysique
energy pathways in N,O
ALAMICHEL
Moleculaire
and A.
PICARD-BERSELLINI
du CNRS, Batiment Cedex, France
(Received 16 December
213, Universitt
de Paris-Sud,
91405 Orsay
1982)
Abstract-In previous papers a method has been proposed to find out the relative importance of the different paths in the decay of the vg mode of N,O, but the VT transfer constants involved in the kinetic model were barely known. As new values of VT constants have just been measured, the calculations of the kinetic model have been performed again; they qualitatively confirm the results already obtained with estimated VT
constants.
In our previous papers [l, 21, we had proposed a method to find out the relative importance of the different paths in the decay of the v3 mode according to the collision reaction: N,O(OOl) + M -+ N,O(OmO)
+ M.
which is quite close to the value estimated in [2] and K,= 1-o (N,O) = 2950 f 500 s- ’ torr- ‘, which is quite different from the value we used in [2] and whose accuracy we have overestimated. If we consider that only one process happens in the exchange vj + v2, we find variances 29 V for m = 1, 6 L’ for m = 2 and 7 V for m = 4, if V is the variance for m = 3. So the m = 3 process is still dominating in reaction (1); the value found for KVJ, j,2 is 2300 f 200 s-l torr-‘, instead of 2150 in [2]. If we now consider that two processes may happen at the same time in the collision reaction (l), then we again find that only the process m = 2 may happen with process m = 3, the other processes (m = 1 or 4) being negligible; however the dispersion of the values found for K ‘lI_ 2,,, remains too important. So the new measurements of the VT constants do not change qualitatively the conclusions of [2], but the value 2150 + 200 s- ’ torr- ’ previously found for K ,,,_ 3v,r must be replaced by 2300 + 200.
(1)
In this method, the vj mode is populated by collisions with activated nitrogen; then, its decay is attributed to vibrational exchange with the v2 mode through the reaction (l), and finally the v2 mode decays through VT transfer. These exchanges are described by a set of differential equations whose integration gives the mean numbers of v2 and v3 quanta per N,O molecule as functions of time {X,(t) and X,(t) functions of [Z]}. Thevalues ofthe K,,,,,,i transfer constants, giving the best fit between the measured and calculated X,(t) and X,(t) functions, are obtained by a least squares method. We had thus found that the process with m = 3 is dominating in reaction (1) and that the process with m = 2 is more important than processes with m = 1 or 4. When we wrote our papers [l, 21 several VT transfer constants, involved in these differential equations cited above, were not well known. Since then, new values have been obtained at 300 and 400 K [3,4] for the (N2) and K,>= 1 _0 (N,O) constants of &,=I-o the collision reaction: N,O (010) + M + N,O(OOO) + M,
REFERENCES
(2)
with M = N, or N,O. So, if these constants follow a law of variation with temperature like K, exp (cL-“~) we must take at 450 K: K,>= 1-o (N2) = 1770+ 100 s-l torr-‘,
661
PICARD-BERSELLINI, C. ROSSETTI and C. BOULET, Spectrochim. Arta 34A, 1607 (1978). PI C. ALAMICHEL and A. PICARD-BERSELLINI, Chem. Phys. 35, 381 (1978). [31 F. LEPOUTRE and N. R. DA &v&Theory and Experiment on Non-Condensed Matter (edited by C. K. N. PATEL~~~ A. MACLELLAND), to be published. [43 N. R. DA SILVA and M. H. DE VASCONCELOS, Physica B 106C, 142 (1981).
Cl1A.
0584-8539183 S3.M)+ 0.M) Q 1983Pergamon PressLtd.
Vibrational C. Laboratoire
de Photophysique
energy pathways in N,O
ALAMICHEL
Moleculaire
and A.
PICARD-BERSELLINI
du CNRS, Batiment Cedex, France
(Received 16 December
213, Universitt
de Paris-Sud,
91405 Orsay
1982)
Abstract-In previous papers a method has been proposed to find out the relative importance of the different paths in the decay of the vg mode of N,O, but the VT transfer constants involved in the kinetic model were barely known. As new values of VT constants have just been measured, the calculations of the kinetic model have been performed again; they qualitatively confirm the results already obtained with estimated VT
constants.
In our previous papers [l, 21, we had proposed a method to find out the relative importance of the different paths in the decay of the v3 mode according to the collision reaction: N,O(OOl) + M -+ N,O(OmO)
+ M.
which is quite close to the value estimated in [2] and K,= 1-o (N,O) = 2950 f 500 s- ’ torr- ‘, which is quite different from the value we used in [2] and whose accuracy we have overestimated. If we consider that only one process happens in the exchange vj + v2, we find variances 29 V for m = 1, 6 L’ for m = 2 and 7 V for m = 4, if V is the variance for m = 3. So the m = 3 process is still dominating in reaction (1); the value found for KVJ, j,2 is 2300 f 200 s-l torr-‘, instead of 2150 in [2]. If we now consider that two processes may happen at the same time in the collision reaction (l), then we again find that only the process m = 2 may happen with process m = 3, the other processes (m = 1 or 4) being negligible; however the dispersion of the values found for K ‘lI_ 2,,, remains too important. So the new measurements of the VT constants do not change qualitatively the conclusions of [2], but the value 2150 + 200 s- ’ torr- ’ previously found for K ,,,_ 3v,r must be replaced by 2300 + 200.
(1)
In this method, the vj mode is populated by collisions with activated nitrogen; then, its decay is attributed to vibrational exchange with the v2 mode through the reaction (l), and finally the v2 mode decays through VT transfer. These exchanges are described by a set of differential equations whose integration gives the mean numbers of v2 and v3 quanta per N,O molecule as functions of time {X,(t) and X,(t) functions of [Z]}. Thevalues ofthe K,,,,,,i transfer constants, giving the best fit between the measured and calculated X,(t) and X,(t) functions, are obtained by a least squares method. We had thus found that the process with m = 3 is dominating in reaction (1) and that the process with m = 2 is more important than processes with m = 1 or 4. When we wrote our papers [l, 21 several VT transfer constants, involved in these differential equations cited above, were not well known. Since then, new values have been obtained at 300 and 400 K [3,4] for the (N2) and K,>= 1 _0 (N,O) constants of &,=I-o the collision reaction: N,O (010) + M + N,O(OOO) + M,
REFERENCES
(2)
with M = N, or N,O. So, if these constants follow a law of variation with temperature like K, exp (cL-“~) we must take at 450 K: K,>= 1-o (N2) = 1770+ 100 s-l torr-‘,
661
PICARD-BERSELLINI, C. ROSSETTI and C. BOULET, Spectrochim. Arta 34A, 1607 (1978). PI C. ALAMICHEL and A. PICARD-BERSELLINI, Chem. Phys. 35, 381 (1978). [31 F. LEPOUTRE and N. R. DA &v&Theory and Experiment on Non-Condensed Matter (edited by C. K. N. PATEL~~~ A. MACLELLAND), to be published. [43 N. R. DA SILVA and M. H. DE VASCONCELOS, Physica B 106C, 142 (1981).
Cl1A.