Temperature dependence of vibrational energy transfer in NH3and H2thinsp;18O

摘要

TheVrarr;T,Rrelaxation rate for NH3thinsp; (ngr;2) has been studied from 198 to 398thinsp;deg;K by the method of laserhyphen;excited vibrational fluorescence. The selfhyphen;deactivation rate constant decreases from 4.9times;10minus;11cm3thinsp;moleculeminus;1thinsp;secminus;1at 198thinsp;deg;K to 2.7times;10minus;11cm3thinsp;moleculeminus;1thinsp;secminus;1at 398thinsp;deg;K. The rate constants for deactivation by He, Ar, N2, and O2are much smaller and show a weak temperature dependence in the opposite direction. For H2thinsp;18O the vibrational relaxation rates of the coupled ngr;1, ngr;3stretching level manifold and of the 2ngr;2bending level have been studied from 250 to 400thinsp;deg;K. The ngr;1, ngr;3selfhyphen;deactivation rate goes from 3.5times;10minus;11cm3thinsp;moleculeminus;1thinsp;secminus;1at 250thinsp;deg;K to 2.0times;10minus;11cm3thinsp;moleculeminus;1thinsp;secminus;1at 400thinsp;deg;K. For 2ngr;2it goes from 1.2times;10minus;10to 7.8times;10minus;11cm3thinsp;moleculeminus;1thinsp;secminus;1. The temperature depencence of the deactivation of both levels by He and Ar is much weaker and the rates are several hundred times slower. CO2deactivates ngr;1, ngr;3about 50 times faster than He or Ar at 293thinsp;deg;K.