DISSOCIATION DYNAMICS OF FAST NEUTRAL H2 BEAMS INCIDENT AT GLANCING ANGLES TO CU(111)

被引:20
作者
HARDER, R [1 ]
NESBITT, A [1 ]
GOLICHOWSKI, A [1 ]
HERRMANN, G [1 ]
SNOWDON, KJ [1 ]
机构
[1] UNIV OSNABRUCK,FACHBEREICH PHYS,D-49069 OSNABRUCK,GERMANY
关键词
D O I
10.1016/0039-6028(94)91128-2
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
We have applied the technique of translational spectroscopy to a study of the dissociation dynamics of fast (0.2-0.5upsilon(F)) neutral H-2 beams incident at normal energies from 0.2-8 eV to a Cu(111) surface. Translational energy losses of the order of 1-10 eV/fs in the close coupling region are observed. We only see indirect evidence for surviving molecules at the lowest beam velocities. ''Mechanical'' excitation processes directly related to the intrinsic crystal corrugation do not appear to be responsible for dissociation. We see no clear signature of known features of the H-2/Cu(111) adiabatic ground state potential energy surface in the scattered atom distributions. The spectra are in fact very similar to those obtained under identical conditions using ionized H-2+ beams in the accompanying paper [Surf. Sci. 316 (1994) 63]. The spectral features and their dependencies on incident beam energy, normal energy and centre-of-mass scattering angle are, as for H-2+ scattering, well reproduced by a simulation which assumes that the H-Cu interaction is purely repulsive, and that the H-H interaction is either purely repulsive or even attractive. We propose that the state or states with this effective topography are in fact excited electronic states of the H-2/Cu system, and that repeated transitions to and relaxation of these states occurs during the dissociative scattering trajectory. Classical trajectory simulations of this potential surface hopping mechanism suggest that the mean propagation time on the upper state per cycle is at least as large, if not larger, than the mean propagation time per cycle on the ground state.
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页码:47 / 62
页数:16
相关论文
共 79 条
[1]  
Amirav A., 1990, Comments on Atomic and Molecular Physics, V24, P187
[2]  
[Anonymous], 1978, ADV CHEM PHYS, DOI DOI 10.1002/9780470142561.CH1
[3]   THE INTERACTION OF NO AND CO WITH CU(111) [J].
BALKENENDE, AR ;
GIJZEMAN, OLJ ;
GEUS, JW .
APPLIED SURFACE SCIENCE, 1989, 37 (02) :189-200
[4]   MOLECULAR-BEAM STUDY OF APPARENT ACTIVATION BARRIER ASSOCIATED WITH ADSORPTION AND DESORPTION OF HYDROGEN ON COPPER [J].
BALOOCH, M ;
CARDILLO, MJ ;
MILLER, DR ;
STICKNEY, RE .
SURFACE SCIENCE, 1974, 46 (02) :358-392
[5]   GAS-SURFACE INTERACTIONS AND DYNAMICS; THERMAL ENERGY ATOMIC AND MOLECULAR BEAM STUDIES [J].
Barker, J. A. ;
Auerbach, D. J. .
SURFACE SCIENCE REPORTS, 1984, 4 (1-2) :1-99
[6]   AN INVESTIGATION OF VIBRATIONALLY ASSISTED ADSORPTION - THE CASES H-2/CU(110) AND H-2/AL(110) [J].
BERGER, HF ;
RENDULIC, KD .
SURFACE SCIENCE, 1991, 253 (1-3) :325-333
[7]   A SEARCH FOR VIBRATIONAL CONTRIBUTIONS TO THE ACTIVATED ADSORPTION OF H-2 ON COPPER [J].
BERGER, HF ;
LEISCH, M ;
WINKLER, A ;
RENDULIC, KD .
CHEMICAL PHYSICS LETTERS, 1990, 175 (05) :425-428
[8]   CONSTRUCTIVE INTERFERENCE EFFECTS IN ENERGY-LOSS SPECTRA OF ENERGETIC NOBLE-GAS IONS AND ATOMS INCIDENT AT GLANCING INCIDENCE TO METAL-SURFACES [J].
BILIC, A ;
GUMHALTER, B ;
MIX, W ;
GOLICHOWSKI, A ;
TZANEV, S ;
SNOWDON, KJ .
SURFACE SCIENCE, 1994, 307 :165-171
[9]   INELASTIC PROCESSES ON MOLECULE-SCATTERING BY SOLID-SURFACES [J].
BITENSKY, IS ;
PARILIS, ES ;
WOJCIECHOWSKI, IA .
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 1993, 73 (03) :333-340
[10]   MOLECULAR VIBRATION DYNAMICS IN MOLECULE SURFACE INTERACTIONS [J].
BRENIG, W ;
KUCHENHOFF, S ;
KASAI, H .
APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 1990, 51 (02) :115-120