Measurements of the HF vibration-vibration transfer time and apparent vibration decay rate ofv = 2using observation of the v = 2 v = 1 fluorescence in HF

Abstract

An experiment resulting in measurement of vibration to vibration transfer rate in pure HF is described. The technique involves pumping a sample cell containing pure HF with an HF chemical laser oscillating on a \upsilon = 1 \rightarrow \upsilon = 1 transition, and then using a filter cell monoehromator combination to separate the \upsilon = 2 \rightarrow \upsilon = 1 fluorescence from that of \upsilon = 1 \rightarrow \upsilon = 0 . An analytic model yielding the time resolved \upsilon = 2 \upsilon = 1 fluorescence is also developed. This model indicates that the rise time of the observed \upsilon = 2 \rightarrow \upsilon = 1 fluorescence gives a direct measurement of the vibration-vibration transfer rate, out of \upsilon = 2 ; that is, the process HF( \upsilon = 2 ) + HF (\upsilon = 0) \rightarrow 2 HF( \upsilon = 1 ). In addition it shows that the population of \upsilon = 2 is proportional to its rate of production and hence to the population in the \upsilon = 1 state squared. As a result the apparent decay rate of our observed \upsilon = 2 fluorescence is twice that for \upsilon = 1 . We find good agreement between these predictions and the results of the time resolved fluorescence experiments. The implication of these results to previous measurements of HF V-T (or V-R) relaxation rate is discussed briefly.