RESONANCE-ENHANCED MULTIPHOTON IONIZATION SPECTROSCOPY OF X(1)SIGMA(-MONOXIDE USING ELECTRON-STIMULATED DESORPTION AS A SOURCE FOR ROVIBRONICALLY EXCITED SPECIES() AND A (3)PI CARBON)

Electron stimulated desorption from CO monolayers chemisorbed on trans ition metal surfaces and from condensed CO layers. were utilized as ne w sources for the production of nonthermal rovibrational distributions of CO probed by resonance-enhanced multiphoton ionization spectroscop y (REMPI). Highly vibrationally excited ground state CO molecules were studied by (1+1)-REMPI via the A(1) Pi and D' (1) Sigma(+) intermedia te states, and metastable CO via the b(3) Sigma(+) and c(3) Pi interme diate states. Rotationally resolved (1+1) spectroscopy via A(1) Pi (up silon' greater than or equal to 20) allowed the verification of the in termediate term energies, including the existence of a potential barri er for the A(1) Pi state. (1+1) spectroscopy via D' (1) Sigma(+) is sh own to provide the possibility to directly probe the D' (1) Sigma(+) p otential curve. Additional spectral features accompanying the b(3) Sig ma(+)<--a(3) Pi (1+1) spectra which cannot be explained by known pertu rbations were found. In gas phase (2+1) spectroscopy via the B-1 Sigma (+) and C' Sigma(+) intermediate states, O- and S-branches could be de tected even with linearly polarized light at very low CO densities (so me 10(-6) Pa). (C) 1996 American Institure of Physics.