Laser Photofragment Spectroscopy of Carbon-Hydrogen Ion and Positively Charged Silicon-Dihydrogen

Available from UMI in association with The British Library. Requires signed TDF. Laser photofragment studies have been carried out on the molecular ions, CH^+ and SiH_2^+. The experiments involved irradiating a mass selected fast-ion-beam of the parent molecular ion with tunable dye laser radiation and the subsequent detection of photofragment ions. For CH^+, C^+ photofragments were detected following the excitation from X^1Sigma^+ ground state levels to rotationally quasibound levels of the A ^1Pi state. Frequencies and linewidths of the resonances were measured for ^{12}CH^+, ^{13}CH^+ and CD^+. The data is used in the evaluation of various models of the dissociation dynamics involving tunnelling through a rotational barrier in the effective potential curve and coupling to other electronic states via non-adiabatic interactions. A new electronic band system has been proposed for the dense region of photofragment lines around 540 nm. This involves excitation of transitions between bound triplet levels just below the first two dissociation limits C^+(^2P) + H and C(^3P) + H^+ . C^+ fragments are detected following radiative decay into the near-threshold continua above the C^+(^2 P) + H limit. For SiH_2^+, high resolution single mode photofragment spectra have been recorded for Sigma sub-bands of the A-B_1-X^2A _1 system. For one band at 18,380 cm^{-1} a rotationally dependent branching into the two channels, Si^+ and SiH^+, seems to occur. In addition a band system consisting of simple rotational branches has been observed in both photofragment channels right across the wavenumber region scanned (16,500-18,700 cm^{-1}). These are believed to originate from transitions between highly excited bending levels of the X and A states.