2ND HARMONIC-GENERATION OF CO2-LASER RADIATION AND FTIR SPECTROSCOPY FOR RESONANT DESORPTION IN THE ADSORBATE CO-NACL(100)

Second harmonic generation of CO2-laser radiation with tellurium and AgGaSe2 single crystals in far field for surface spectroscopy and resonant desorption was performed. Polarized FTIR and laser spectra of the adsorbate CO-NaCl(100) as well as its ordered structure p(1 X 1) are presented. Isosteric heats of adsorption were found to be smaller than the energy of the fundamental internal vibration of the adsorbed CO. Vibrational excitation results in exciton motion of the ordered adsorbate. Laser-induced vibrational predesorption has been observed. From the vibrational linewidth of 0.15 cm-1 for CO-NaCl(100) at 17 K, the smallest known under these conditions for adsorbed CO, the upper limit 1010 s-1 of the rate coefficients for all relaxation processes including vibrational predesorption follows. © 1990.