Abstract

The main purpose of this paper is to propose theoretically a new type of molecular spectroscopy based on the measurement of the IR laser-stimulated desorption yield as a function of laser frequency. For this purpose we have investigated the band shape, bandwidth, band shifts, and selection rules of this laser-stimulated desorption molecular spectroscopy (LSDMS). In contrast with the traditional molecular spectroscopy that has the Lorentzian band shape in the homogeneous broadening, the LSDMS usually exhibits the Beutler-Fano asymmetric band shape because of the coupling between the excited state of the intramolecular optically pumped mode with the desorption continuum. If there is more than one adsorption site (or if the surface is not homogeneous), then the observed LSDMS band shape will be the superposition Beutler-Fano asymmetric bands. The theory has been applied to analyze the experimental results of the CO₂ laser-stimulated desorption of pyridine molecules adsorbed on the Ag surface.

© 1987 Optical Society of America

Theory of photodesorption by infrared-laser–adsorbate coupling

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