| Blackbody radiation has been used to vibrationally excite diatomic molecules dissolved in simple cryogenic liquids. Observation of the infrared emission from these diatomics made it possible to monitor the vibrational relaxation of the solutions. The spectral distribution of the emission for some of the systems was also investigated.;By adding O(,2) to the Ar-CO system we are able to compare the vibrational relaxation of CO* by O(,2) dissolved in liquid Ar at 85K with gas phase vibrational relaxation data for the same process at the same temperature. This comparison allows us to make a quantitative test of the widely applied Isolated Binary Collision model of liquids.;Vibrational relaxation of dilute solutions of CO in liquid Ar and CO in liquid N(,2) were found to be dominated by radiative processes. The radiative relaxation rate of CO in liquid N(,2) was found to be k(,CO*,rad)(liquid N(,2)) = 51 (+OR-) 5 sec('-1) while the rate in liquid Ar was observed to be k(,CO*,rad)(liquid Ar) = 55 (+OR-) 2 sec('-1). The system of neat liquid N(,2) was found to relax by means of both radiative and non-radiative (vibrational-rotational, translational) means with an observed relaxation rate of 0.022 (+OR-) .002 sec('-1). This corresponds to a lifetime of 45 seconds. This relaxation rate allowed us to place an upper limit on the non-radiative decay of N(,2)* (N(,2) excited to the first vibrational level) by N(,2) of k(,N(,2)*,N(,2)) (LESSTHEQ) 6 x 10('-25) cm('3) molecule('-1) sec('-1). For this neat liquid N(,2) solution the relaxation was followed by observation of the collision induced emission of the N(,2) fundamental. The observed relaxation rate of neat liquid CO was 1.1 (+OR-) .1 sec('-1). This rate, which because of radiation trapping of the CO emission is smaller than the radiative rate of liquid CO, allows us to place a limit on the vibrational-translational, rotational relaxation rate of CO* by CO, k(,CO*,CO) (LESSTHEQ) 6.5 (+OR-) .5 x 10('-23) cm('3) molecule('-1) sec('-1). The vibrational relaxation behavior of these liquid systems (N(,2), CO, N(,2)-CO, Ar-CO) is extensively discussed and compared to various theoretical predictions. The radiation trapping phenomenon observed in the liquid CO, N(,2)-CO, and Ar-CO systems is modeled and the observed relaxation rate behavior qualitatively explained. |
