Molecular Jet Study of Aniline-Helium van der Waals Molecules and Aniline Radiationless Relaxation in the(1) B sub 2 Excited Electronic State

摘要

Fluorescence excitation (FE), dispersed emission (DE), and time of flight mass spectroscopy (TOFMS) techniques are employed to study the van der Waals molecules formed in a molecular supersonic jet of aniline and helium (AnHe sub x). It is found that AnHe1, AnHe2, and AnHe3 have absorption bands that fall under all the An(nu') vibronic features in the 1B2 electronic state of An. The features to the high energy side of the An vibronic transitions are tentatively associated with vibrations of the above van der Waals molecules. The DE from both An and AnHe sub x can be characterized as either relaxed or unrelaxed depending on whether or not the aniline vibronic state emitting is the same as or different from that which was pumped. All relaxed An emission can be associated with vibrational predissociation of the AnHe sub x species. All unrelaxed emission from AnHe sub x (nu' +v), with nu' = An sub x mode and v = vdW bond mode, can be associated with delta v = 0 transitions from AnHe sub x. A number of other relaxation mechanisms are presented and discussed including collisional ones. Some time estimates for the major processes can be discussed.