Knowledge Bank

The well-known emission bands produced by addition of foreign gases to iodine vapor, excited into the $v\prime =25,J1=34$ level of the $B3II0u\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ state by the mercury green $line1-5$, have been examined with a high-speed, high-resolution photoelectric spectrometer, under conditions of low gas pressures. This has permitted the accurate measurement of cross-sections for quenching, vibrational and rotational energy transfer and depolarization by a wide variety of collision partners. The data have been corrected for self-absorption and for the variation of Franck-Condon factors and radiative lifetimes. Among the results to be presented are: i. evidence for an electrostatic quenching mechanism, in addition to the previously known magnetic $mechanism6$; ii. relative cross sections for the transfer of $\pm 1$ and $\pm 2$ vibrational quanta for the different gases studied; iii. observation of transfer up to fifty rotational quanta by a single collision, and the variation of the energy transfer cross section as a function of the change in rotational angular momentum, with varying degrees of vibrational energy transfer and different foreign gases. These results will be discussed in terms of models for inelastic scattering processes and the intermolecular potential for the electronically excited states; implications for several problems in chemical kinetics will also be discussed.