Photostimulated desorption of NO chemisorbed on a Pt(100) surface at 80 and 300 K has been studied with an ArF excimer laser (lgr;=193 nm) and a positivehyphen;ion measurement system. NO+is the only ion species observed when a NOhyphen;saturated Pt(100) surface is irradiated with laser light. The NO+yield is proportional to the third power of laser fluence. The translationalhyphen;energy distribution of the NO+ions is independent of laser fluence. We propose a twohyphen;step model as the most probable NO+formation mechanism. The first step is desorption of neutral NO induced by valencehyphen;electron excitation in chemisorbed NO with onehyphen;photon absorption. Then, the desorbed NO is ionized in the vicinity of the surface via the twohyphen;photon nonresonant ionization process. Relatively large desorption cross sections estimated from the decay of the NO+yield support the above NO+formation mechanism.
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