Internal energy distributions resulting from sustained off-resonance excitation in FTMS. I. Fragmentation of the bromobenzene radical cation

Collision energy resolved study of the fragmentation of C6H5Br+ was carried out using both on-resonance and sustained off-resonance excitation. Fragmentation efficiency curves were obtained as a function of collision energy under single- and multiple-collision conditions. The results were modeled using the Rice-Ramsperger-Kassel-Marcus/quasi-equilibrium theory (RRKM/QET) formalism. An analytical form for the collisional energy deposition function is proposed. Experimental results obtained in both on-resonance single-collision and sustained off-resonance irradiation (SORI) experiments could be reproduced within the same theoretical model. The influence of the center-of-mass collision energy and pressure on energy transfer is demonstrated. (C) 2000 Elsevier Science B.V.