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

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.