Atom-molecule scattering

Light, J.C. and Walker, R.B. (1976). An R-matrix approach to the solution of coupled equations for atom-molecule scattering, J. Chem. Phys. 65,4272-4282. 

Semiclassical procedures which give results in quantitative agreement with the exact quantum results over the whole angular range have been published only recently (Berry, 1966 Miller, 1968 Berry, 1969 Mullen and Thomas, 1973 Mount, 1973). Therefore we start with a description of such a uniform semiclassical approximation (Section III.A). Next, all cross section features are summarized. Their dependence on the reduced energy and reduced wave number as well as their sensitivity to the potential are discussed in Section III. B. Finally, the influence of other than spherically symmetric interactions such as anisotropic potentials occurring in atom-molecule scattering or any kind of inelasticities and chemical reactions are studied (Section III.C). 

In this chapter reactive scattering for chemical systems shall be emphasized. Though the methods developed are much more general, they can, of course, treat nonreactive scattering in such systems as well. Additionally they can be fruitfully applied to computing resonances and transmission coefficients in quantum electronic devices (5) to electron-atom (molecule) scattering to problems involving atom (molecule) continuum processes even when they are in the presence of a laser field (6), etc. 

The work and analysis reported in Refs. [123,124], took the scope and the accuracy of fhe fheory and compufafion of electron-atom (molecule) scattering resonances to an unprecedented level for the standards of the field, in order fo achieve fhe firsf definifive resolution and interpretation of fhe spectrum of fhe complex poles representing the resonance states of H . 

Bohn, J.L., Molecular spin relaxation in cold atom-molecule scattering, Phys. Rev. A, 61, 040702, 2000. 

L. D. Thomas, Solution of the coupled equations of inelastic atom-molecule scattering for a single initial state, J. Chem. Phys. 70 2979 (1979). 

M. Baer, G. Drolshagen, and J. P. Toennies, The adiabatic-diabatic approach to vibrational inelastic scattering. I, Theory and study of a simple collinear model, J. Chem. Phys. 73 1690 (1980) N. M. Harvey and D. G. Truhlar, Use of vibrationally adiabatic basis functions for inelastic atom-molecule scattering, Chem. Phys. Lett. 74 252 (1980). 

U. Buck, F. Gestermann, and H. Pauly, Double rainbows in atom-molecule scattering, Chem. Phys. Lett. 33 186 (1975). 

The dangling bonds of a Si surface abstract one F atom from an incident F2 molecule while the complementary F atom is scattered back into the gas phase [20]. This abstractive mechanism leads to F adsorjDtion at single sites rather than at adjacent pairs of sites, as observed directly by scanning tunnelling microscopy [21]. Br atoms adsorb only to Ga atoms in the second layer of GaAs(001)-(2 x 4) where empty dangling bonds on the Ga atoms can be filled by electrons from the Br atoms [22]. 

Here, AT is a constant, f is the incoming intensity, R is the distance of the scattered wave from the molecule (in practical terms, it is the distance between the scattering center and the point of observation), i and j are the labels of atoms in the jV-atomic molecule, g contains the electron scattering amplitudes and phases of atoms, 5 is a simple function of the scattering angle and the electron wavelength, I is the mean vibrational amplitude of a pair of nuclei, r is the intemuclear distance r is the equilibrium intemuclear distance and is an effective intemuclear distance), and k is an asymmetry parameter related to anharmonicity of the vibration of a pair of nuclei. 

Consider a molecule prepared in the absolute ground state in the absence of the field and subjected to microwave field of frequency . If collided with a structureless atom in the absence of the field and at collision energies below the first excitation threshold, the molecule can undergo only elastic scattering. In the presence of the field, the ground state of the molecule becomes a field-dressed state X). And for every field-dressed state X), there is an infinite number of replica states 2 - A ), lower in energy. The states 2 - A ) and X) are coupled by the anisotropy of the atom-molecule interaction potential, so collisions can induce... 

Figure 3.6. Schematic of the cube model for energy transfer ( ) of an atom/molecule of mass m incident with energy Et to the lattice represented by a cube of mass Ms. The atom/molecule adsorption well depth is W. The double arrow labeled Ts emphasizes that the cube also has initial thermal motion in the scattering.

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