Pulsed visible laser photolyis of B(C2H5)3, Al2(CH3)6, Ga(CH3)3, and In(CH3)3: Multiphoton ionization spectra of Al, Ga, and In atoms

Abstract

Multiphoton dissociation/ionization of the title compounds by focused visible laser pulses (390<λ<650 nm, 107–1010 W/cm2) has been investigated by use of a low-pressure (≂1 Torr) ionization cell. Al2(CH3)6, Ga(CH3)3, and In(CH3)3 fragment in the laser pulse to produce ground state and excited neutral metal atoms, which were detected by resonance-enhanced two- or three-photon ionization within the photolysis laser pulse. The observed MPI spectra are thus characteristic of the metal atoms, and carry information on the relative abundances of ground and excited state metal atoms produced in the fragmentation process. Analysis of these spectra provided new information on the np1 2PJ and nf1 2FJ Rydberg series of Al(I), Ga(I), and In(I). Evidence is presented to indicate that under relatively high visible laser flux conditions B(C2H5)3 undergoes a direct multiphoton ionization process to form the molecular ion.