Polarization and Mhyphen;dependent effects in rotationally inelastic collisions of openhyphen;shell diatomic molecules: Arndash;NO(Xthinsp;2Pgr;1/2)

摘要

Our earlier quantum study of collisions of NO(Xthinsp;2Pgr;) with Ar lsqb;T. Orlikowski and M. H. Alexander, J. Chem. Phys.79, 6006 (1983)rsqb; is here extended to the calculation ofMhyphen;dependent cross sections in the case of laboratoryhyphen;frame quantization, as would be appropriate to collision cell experiments. The calculations confirm the earlier prediction of Alexander and Davis lsqb;J. Chem. Phys.79, 227 (1983)rsqb; that the JMrarr;J, hyphen;M cross sections will be vanishingly small for transitions which preserve theeorfLgr;hyphen;doublet symmetry. This propensity rule is here shown to be rigorous within the coupledhyphen;states (CS) limit. The effect of collisions on the initial rotational density matrix can be expressed in terms of multipole transfer efficiencies. The calculated values for Arndash;NO collisions indicate thate/fchanging collisions are much more strongly depolarizing, in the sense of destroying the multipole moments of the initial density matrix, than those collisions which preserve thee/fLgr;hyphen;doublet label. Since the circular or linear polarization of the fluorescence from a laser excited molecule can be written in terms of these multipole transfer efficiencies, we are able to use the Arndash;NO(Xthinsp;2Pgr;) cross sections reported here to model qualitatively the depolarization effects one might expect to see in experiments involving excited molecules in2Pgr; electronic states.