Collisionhyphen;induced transitions from N2(Arsquo;thinsp;5Sgr;+g) to N2(Bthinsp;3Pgr;g) via the gateway mechanism

摘要

A beam containing N2in longhyphen;lived states was allowed to interact with target particles in a collision cell. Intramolecular transitionsArarr;BandWrarr;Bare induced, such as were studied earlier by us by means of the subsequentBrarr;Aemission lsqb;R. Bachmann, X. Li, Ch. Ottinger, and A. F. Vilesov, J. Chem. Phys.96, 5151 (1992)rsqb;. In the present work the product emission was observed under high resolution (1 Aring; FWHM). Most of theBrarr;Abands show the typical quasithermal rotational contours. However, in the emissions from theBstate vibrational levelv=10 sharp superimposed features were observed. They were assigned to transitions from the rotation/fine structure/Lgr; sublevel3Pgr;e2(12). This particular level is perturbed by theArsquo;thinsp;5Sgr;+gstate, serving as a sohyphen;called gateway to allow the otherwise spinhyphen;forbidden5Sgr;+grarr;3Pgr;gcollisionhyphen;induced transition. According to this mechanism, the collisions scramble only the levels within theArsquo;state, while theArsquo;rarr;Btransition occurs spontaneously through S/O coupling. A similar, less well characterized perturbation was also found for theB,v=12,3Pgr;e0(16) level. Apart from the gateway mechanism, any direct collisional coupling between theArsquo;andBstates appears to be insignificant. This result is contrary to one of the longhyphen;standing assumptions on the origin of the Lewisndash;Rayleigh nitrogen afterglow.