Knowledge Bank

We have used a new $technique1$ to measure the velocity dependence of the Rotational Energy transfer (RET) rate constants for the process [Na^{}{2}(j{i}) + Xe \to Na^{}{2}(j{i} + \Delta) + Xe] Where $ji$ is the initial rotational quantum number and is the change in rotational quantum number. By tuning a single-mode dye laser across the Doppler profile of a molecular resonance we can very the average relative velocity from $450\circ K$ (line center) to $2400\circ K$ (=2 Ghz. detuned). We made $measurements2$ for four different values of $\Delta$ for each of three $Ji$’s. Cross sections for $ji=66$ increase with velocity whereas those for $ji=38$ and 16 stay constant or decrease. A dramatic decrease is observed for $ji=164$ and large $\Delta$.