TY - JOUR
T1 - An adiabatic model of chemisorbed molecules
T2 - electron spectroscopy and excited-state potential-energy surfaces
AU - Jennison, D. R.
AU - Stechel, E. B.
AU - Burns, A. R.
N1 - Funding Information:
Who cares about understanding spectroscopy? We are approaching the ability to theoretically model surface dynamical processes relevant to materials growth, chemical-mechanical effects, and catalysis. Advances in ab initio techniques, such as gradient-corrected LDA functionals \[1\], and advances in supercomputing, such as new massively-parallel codes \[2\]p, ermit realistic studies of systems with literally hundreds of atoms per unit cell. Furthermore, it can be argued that understanding the technologically important processes mentioned above requires knowledge of only ground-state potential energy surfaces (PESs). But how do we test our knowledge of these hypersurfaces for real adsorbate systems?* Photon and electron-beam stimulated processes, such as desorption, dissociation, and chemical reactions \[3\],a re now studied with quantum-state specificity by detecting the products with laser-spectroscopies, such as REMPI \[4\]. Such experiments potentially provide a wealth of information about ground and excited-state PESs, dynamics, and *Work at Sandia National Laboratoriesw as supportedb y the U.S. Department of Energy under Contract DE-ACO4-94AL85000.
PY - 1995/3/31
Y1 - 1995/3/31
N2 - We review models that have been used to understand excited states of chemisorbed species, focussing on CO and NO, and encounter problems in attempting to fit all observables. We then introduce a new model. We show that a purely-electronic adiabatic approximation leads to an accurate solution for the system wavefunction in the limit that the molecule-substrate interaction is weak. This produces a configuration-interaction theory that has a Hubbard-like form. We derive semi-empirical parameters for the NO:Pt(111) system and find that the transfer integral for the 2π-substrate interaction is small for all choices of the screened electron-electron interaction, U. This suggests, for this system, that the substrate indeed adiabatically follows the fluctuations in adsorbate charge which are inherent in a covalent bond. We propose that our model is robust and applies to many adsorbed molecules. We then investigate low-lying excited-states of the metal-molecule bond.
AB - We review models that have been used to understand excited states of chemisorbed species, focussing on CO and NO, and encounter problems in attempting to fit all observables. We then introduce a new model. We show that a purely-electronic adiabatic approximation leads to an accurate solution for the system wavefunction in the limit that the molecule-substrate interaction is weak. This produces a configuration-interaction theory that has a Hubbard-like form. We derive semi-empirical parameters for the NO:Pt(111) system and find that the transfer integral for the 2π-substrate interaction is small for all choices of the screened electron-electron interaction, U. This suggests, for this system, that the substrate indeed adiabatically follows the fluctuations in adsorbate charge which are inherent in a covalent bond. We propose that our model is robust and applies to many adsorbed molecules. We then investigate low-lying excited-states of the metal-molecule bond.
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U2 - 10.1016/0368-2048(94)02293-3
DO - 10.1016/0368-2048(94)02293-3
M3 - Article
AN - SCOPUS:0003366255
VL - 72
SP - 9
EP - 18
JO - Journal of Electron Spectroscopy and Related Phenomena
JF - Journal of Electron Spectroscopy and Related Phenomena
SN - 0368-2048
IS - C
ER -