Spherical-complex-optical-potential (SCOP) model for electron–monosilane (SiH4) collisions at 30–400 eV: Total (elastic+absorption), momentum transfer, and differential cross sections

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Abstract
We report nonempirical quantum mechanical calculations on the total (elastic+absorption), momentum transfer, and differential cross sections for e‐SiH4 collisions at intermediate and high energies (30–400 eV). A parameter‐free and energy‐dependent spherical‐complex‐optical potential (SCOP) is evaluated for the e–SiH4 system. The real part of the SCOP consists of three local terms, namely static, exchange, and polarization. The static interaction is generated very accurately from near‐Hartree–Fock one‐center silane wave functions, while the exchange effects are accounted for in the free‐electron‐gas‐exchange (FEGE) model. The polarization potential is evaluated ab initio in a parameter‐free approximation of Jain and Thompson. The imaginary term of the total SCOP represents loss of flux due to inelastic channels via an energy‐dependent absorption potential calculated from target electron density and short‐range static‐exchange force in the quasifree model with Pauli blocking [Staszewska et al.; J. Phys. B 1 6, L281 (1983)]. Two versions of this absorption potential are employed; one with an undistorted density and the other with a polarized density determined approximately from first order target wave functions. The later version is more successful when the final results are compared with experiment. The total SCOP is treated exactly in a partial‐wave analysis using the variable‐phase approach to yield complex phase shifts. Our final total cross sections compare very well with the only available measurements of Sueoka and Mori. However, below 50 eV, present total cross sections overestimate the experimental data within 10%. The effect of absorption potential is to reduce the elastic cross sections significantly; this reduction is more dramatic in case of the differential cross sections (DCS); for example, the reduced DCS are exposed to more pronounced structure. Interestingly, the e–SiH4 reduced DCS are very close in shape to the corresponding e–Ar cross sections above 60 eV.