Multicollision Kinetics of Hot Atoms （D^*） with Small Malecules （CO₂）

In order to describe the collisional deactivation of translational energetic D^* produced in the excimer laser photolysis of D₂S and the vibrational excited CO₂ molecules, a multi-collision kinetic model is used. The relation between vibrational quantum yield （\frac\left\mathrmCO_2\right\left\mathrmD^*\right_0） and the effects of the first, second and third collisions is obtained. When the concentrations of CO₂ in D₂S are larger, the effects of the second, third collisions are bigger.
In the case of CO₂ v₃ vibrational mode, the assumption that the first collision of an initially generated D^* with CO₂ produces the vibrational excitation is within experiment error The effect of the second collision is less than \frac110 of the first collision. And the third collision is less than \frac1100. lt’s negligible.
In the case of CO₂ v₂ vibrational mode, the effect of the second collision in 1D₂S:4CO₂ mixture is about \frac14 of the first collision and the third collision is about \frac116. This result is in agreement with the experiment. This is the reason why the concentrations of CO₂ in D₂S are larger, the quantum yield is bigger.