Vibrational energy transfer in gas phase water and ammonia

The V → T, R relaxation rate for NH3 (ν2) was studied from 1980K to 3980K by the method of laser-excited vibrational fluorescence. The self-deactivation rate constant decreases from 2.4 μsec torr-1 at 1980K to 0.65 μsec-1 torr-1 at 3980K. The rate constants for deactivation by He, Ar, N2, and O2 are much smaller and show a weak temperature dependence in the opposite direction. The vibrational relaxation rates of the coupled ν1, ν3 stretching level manifold and of the 2ν2 bending level in H218O was studied from 2500K to 4000K using th same method as for NH3. The ν1, ν3 self-deactivation rate goes from 1.4 μsec-1 torr-1 at 2500K to 0.48 μsec-1 torr-1 at 4000K. For 2ν2 it goes from 4.5 μsec-1 torr to 1.9 μsec-1 torr-1. The temperature dependence of the deactivation of both levels by He and Ar is much weaker and the rates are several hundred times slower. Deactivation of ν1, ν3 by N2, O2, and CO2 is measured only at 2930K. N2 and O2 deactivate ν1, ν3 about 5 and CO2 about 50 times faster than He or Ar