Jet cooled emission spectra of toluene and the benzyl radical

Abstract

Listen

Translate article

Abstract Rotationally cooled gas-phase electronic emission spectra of toluene and the benzyl radical were produced with a corona excited supersonic expansion. This is the first observation of relatively large molecules in this source. Most of the observed bands in both toluene ( 1 B 2 → 1 A 1 ) and the benzyl radical ( 2 A 2 → 2 B 2 ) are the result of emission from the lowest vibrational level in the electronic excited state. The toluene vibronic assignments were based on the known infrared and Raman vibrational frequencies, while the benzyl radical assignments were based on comparison with the toluene frequencies and previous benzyl radical studies. The absence of significant hot band emission from the excited electronic states in both toluene and benzyl suggests extensive vibrational cooling in the corona excited supersonic expansion source. Transitions from the second electronic excited state (22B2 → 12B2) in benzyl radical were observed, although greatly reduced in intensity. This 22B2 state is highly mixed with the low-lying vibrations of the 12A2 state. The interaction between these electronic excited states introduces a mechanism that allows electronic quenching to occur during the expansion via collisional removal of vibrational energy.