Field desorption spectroscopy fragments

By field ion mass spectroscopy of NH3 on Fe at room temperature, 4 -10"" torr, N Hy species and FeN Hy species are detected [510]. Secondary ion mass-spectroscopy of NH3/Fe(110) at 130 K shows FCnNH " with n, m = 1, 2, with n = 0,1,2, 3,4, H2 and Fe" [545]. The spectrum is interpreted as fragments of molecularily adsorbed NH3 [545]. When the temperature is increased, FeNH and FeNHl decrease smoothly, while Fe increases smoothly, illustrating the decrease in surface coverage and the reaction of NH3(g) with the surface at higher temperatures [545]. The intensity of NH3 with NH2 decreases steeply above 300 K consistent with the temperature programmed desorption studies [545]. Both ions are probably formed from adsorbed species [545]. The intensity of NH" decreases more slowly than NH2 and NH3 the reason is probably that NH" is formed from both NH3(g) and NH [545]. 

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