INTERACTION OF SLOW ELECTRONS WITH CHEMISORBED OXYGEN

Canadian Journal of Physics - Tập 42 Số 5 - Trang 886-905 - 1964
P. A. Redhead

Tóm tắt

Measurements have been made of the effects of low-energy electron bombardment (0–300 ev) on a chemisorbed layer of oxygen on polycrystalline molybdenum. Oxygen is adsorbed in two states at room temperature with approximate heats of adsorption of 60 and 110 kcal/mole, respectively. O+ ions are released from the weakly bound state with a maximum probability of 10−5 ion/electron at an electron energy of 90 ev. The ion-energy distribution, measured by a retarding-field method, has a maximum at about 6 ev and a half-width of 5 ev. About 50 neutrals are released for every ion. The measured threshold energy, 17.6 ± 0.2 ev, for ion formation is in good agreement with the calculated value. The probability of ion and neutral release from the strongly bonded state is about 2 × 103 times smaller than for the weakly bonded state. A qualitative explanation of the formation of neutrals is proposed in terms of Auger neutralization of the ions near the surface. Reflection of the ion-energy distribution in the calculated curve of the potential energy of the O+ ion yields, after correction for Auger neutralization, the probability density distribution of the adsorbed oxygen atom. The equilibrium spacing of the chemisorbed atom is then estimated to be 1.67 Å.

Từ khóa


Tài liệu tham khảo

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