Single collision gas-surface vibrational energy transfer in reactive systems. Variation of initial energy distribution

Abstract

The initial vibrational energy distribution of molecules that collide with a hot surface has been varied. The effect of the variation on the collisional reaction probability (Pc) has been studied under single collision conditions. These experiments provide a more sensitive test of the relative suitability of various analytical forms for the collisional transition probability matrix P than has been achieved previously in earlier VEM experiments. The reaction system is the isomerization of cyclobutene to 1, 3-butadiene. A seasoned fused quartz surface was used over the temperature range Tr = 600–900 K. Variation of the initial vibrational energy population vector of cyclobutene molecules was made by change of their initial temperature Tc in the range 273–620 K. The experimental collisional efficiency β1 declined from 0.31 to 0.013 over the combination temperature ranges Tr, Tc = 600,500 to 900,273. Stochastic models of the vibrational transition probability were fitted to the data and provided values for the average amount of energy (<ΔE′≳E0) transferred from the hot molecules in a down transition from the threshold energy level E0; Gaussian or Boltzmann exponential forms of P prove to be the most suitable to fit the data. Calculated values, <ΔE′≳E0 on the basis of a Gaussian function model for P declined from 5600 to 3700 cm−1 with increase in the surface temperature from 600 to 900 K.