MC7 - Chemical laser studies of vibrational energy distributions: The equal-gain and zero-gain temperature techniques

The Statz and de Mars rate equations applied to gaseous lasers reproduce experimentally observed threshold times, initial pulse spiking, and transient oscillatory behavior. Hence they provide a theoretical basis for the equal-gain temperature method, which is based upon comparison of times to threshold. This method is generalized by use of a grating in the optical cavity to permit selection of any desired pair of transitions for gain comparison. These developments have led us to a new method for fixing vibrational rate constant ratios, the "zero-gain temperature" method. A tandem laser is coupled with a grating so that the "driver" reaction emits just above threshold for any desired transition. Then the change of time to threshold caused by the "slave" reaction indicates whether its gain is positive or negative. The temperature is measured at which zero gain occurs and the vibrational population can then be deduced. The relative advantages of these various methods for learning vibrational distributions in chemical reactions are considered.