Vibrational relaxation measurements in hydrogen fluoride

Abstract

Vibrational relaxation measurements in HF have been obtained at intermediate temperatures by combining the laser induced fluorescence technique with shock compression heating in a shock tube. Usually, shock tube measurements of vibrational relaxation are limited to high temperatures; above about 1300 K in the case of HF. Laser induced fluorescence measurements can be made in heated cells suitable for HF handling up to about 700-800 K. The combination of the two techniques offers several advantages includiug large range of temperatures, no wall reactions nor leaky cells at high temperature. We have used this method to obtain HF vibrational relaxation data at temperatures from 450 to 1030 K as well as at 300 K. These data together with shock tube data at high temperature (1350-4000) K are compared with theoretical predictions. Room temperature measurements with the laser induced fluorescence technique have yielded the relaxation rates of the first four vibrational levels of HF as well as an estimate of the vibration-vibration rate of energy exchange of HF with itself.