The impact of monochromatic low-energy electrons (4-52 eV) is found to
induce desorption of metastable particles (MP) from multilayer films
formed by condensing CO gas on a Pt(111) substrate held at 20 K. The r
esults are compared with metastable production from gaseous CO. Metast
able CO (CO) is identified as the major desorbed species, its desorpt
ion is discussed in terms of intramolecular to molecule-surface vibrat
ional energy transfer. Primary electronic excitation proceeds via the
states, a '(3)Sigma(+), d(3)Delta, e(3)Sigma(-), I(1)Sigma(-), and D(1
)Delta which contribute to MP desorption directly or by first decaying
in high vibrational levels of the a(3)Pi configuration. The energy th
reshold of 8.0 eV for CO desorption indicates that CO in low vibratio
nal levels of the a(3)Pi state does not desorb. Electronic excitation
occurs either near the surface of the CO film or in the bulk. In the l
atter case, excitonic motion to the surface can be followed by CO des
orption. (C) 1998 American Institute of Physics. [S1063-777X(98)00910-
4]