VT relaxation in N2and CO

Using a vibrational pumping technique based on transient stimulated Raman scattering we have measured
p\tau
values for VT relaxation of the
\upsilon = 1
levels in N
2
and CO at room temperature and in the presence of several deactivants; the N
2
data represent the only room temperature data presently available. A mode-locked ruby laser, delivering picosecond pulses, vibrationally pumps the molecule by TSRS; the subsequent decay of the vibrational population is followed by light scattering off localized refractive index changes caused by heating arising from the thermalization of the excited state population. For rapidly relaxing molecules, heat conduction is negligible and the scattered light signal behaves as
(1 - e^{-t}/\tau_{VT})^{2}
Since CO and N
2
relax quite slowly, heat losses can be appreciable; the resulting behavior of the scattered light signal and its relationship to a τ
VT
will be discussed. Thus far
p\tau
values of 6 ± 3 and 0.7 ± 0.35 s-atm have obtained for N
2
and CO, respectively. In addition, data for CO deactivation by CO chemical laser contaminants, such as COS, SO
2
, and CS
2
, and preliminary temperature dependence measurements will be discussed.