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THEORETICAL-STUDY OF NA-ATOM EMISSION FROM NACL (100) SURFACES

PUCHIN, V; SHLUGER, A; NAKAI, Y; ITOH, N; (1994) THEORETICAL-STUDY OF NA-ATOM EMISSION FROM NACL (100) SURFACES. PHYS REV B , 49 (16) 11364 - 11373.

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Abstract

Several models for the elementary processes causing the emission of alkali atoms by electronic excitation of NaCl (100) surfaces have been investigated theoretically. First, the desorption of a Na atom neighboring an electronically excited F center on the surface is simulated using a quantum-mechanical embedded-cluster technique. It is shown that emission of a Na atom is energetically favorable. The kinetics of this process is shown to be controlled by the probability of a nonradiative transition between the two states: the excited state of the F center and that corresponding to a Na atom desorbing from the surface. The potential barrier for desorption of an excited Na atom from the excited F-center state is found to be 2.1 eV. It is also found that the energy for emission of a Na atom from a cluster of F centers (the F3 center) is considerably reduced (for a certain configuration of the defect) with respect to the similar energy for a single F center. The energy barrier for emission of a Na atom neighboring an F' center on the surface is calculated to be 1 eV. It is shown that the electronic excitation of kinklike sites, with a Na atom at the edge, can lead to a barrierless emission of a Na atom, leaving a V(k)-type defect behind. The results of calculations are discussed critically on the basis of existing experimental data.

Type:Article
Title:THEORETICAL-STUDY OF NA-ATOM EMISSION FROM NACL (100) SURFACES
Keywords:ALKALI-HALIDES, ELECTRONIC-STRUCTURE, DEFECT FORMATION, LATTICE-DEFECTS, IONIC-CRYSTALS, SINGLE-CRYSTAL, EXCITATION, DESORPTION, MGO, PARAMETRIZATION
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Physics and Astronomy

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