Vibrational distribution of CO and NO excited by electronic-to-vibrational energy transfer collisions with Hg(6 3P1 and 6 3P)

Abstract

The initial vibrational distributions of CO and NO excited by electronic‐to‐vibrational (E–V) energy transfer collisions with Hg₁^* (Hg in the 6 ³P₁ state) and Hg₀^* (Hg in the 6 ³P₀ state) have been determined by the measurements of the IR emission spectra of CO and NO utilizing a modulation technique. The Hg resonant radiation to excite Hg to Hg₁^* in Ar(N₂) –CO or –NO mixtures was modulated in its intensity with a frequency in the range of 120 Hz to several kHz. Observation of the resulting in‐phase and quadrature components of the IR emission made it possible to separate the contribution of the initial vibrational excitation to each level from that of the vibrational relaxation. In Hg^*₁–CO collisions, Hg₁^*→Hg^*₀ transition occurs with simultaneous excitation of CO to the v=1 level. The fraction of the electronic energy of Hg^* converted to the vibrational energy of CO or NO are 27%, 32%, and 31% for Hg^*₀–CO, Hg^*₁– and Hg^*₀–NO collisions, respectively. The vibrational distributions resemble the Poisson type in agreement with those estimated on the basis of the impulsive ’’half‐collision’’ model. However, in Hg^*₀–CO collisions, the model may not reproduce strictly the observed distribution, in which more populations in levels of v=4, 5, and 6 and less in those of v =1, 2, 8, and 9 are found. Contrary, in Hg^*₁– or Hg₀^*–NO collisions, the model results in a distribution which accords almost with the observed one, though the populations are found in levels of v?12, which exceed the highest level that can be achieved in the impulsive limit. All of the observed distributions deviate significiantly from the statistical prior distribution giving nonlinear surprisal plots.