Time-resolved photodissociation study of relaxation processes in gas-phase styrene ion

Publisher Website
Google Scholar
Abstract
Time-resolved photodissociation of styrene ions at 308 nm was observed in the ion cyclotron resonance ion trap. The rate of m/z 78 product ion formation was shown to be a sensitive function of the internal energy of the dissociating parent ions. The dissociation rates, ranging up to 5×105 s−1, were near the upper limit of the technique, and an improved signal equation was derived for quantitative interpretation of the data. By observing the m/z 78 photoappearance rate as a function of pressure and delay time between electron impact ionization and the laser pulse, the relaxation of initially excited styrene ions was characterized, giving a collisional relaxation rate constant of 4.5×10−10 cc molecule−1 s−1, and an IR radiative relaxation rate constant of 0.65 s−1. At 11.5 eV electron impact ionizing energy the parent ions were found to be formed with an average initial excess internal energy of 0.45 eV.