Vibrationally elastic scattering of positrons from CH4 molecules

Abstract

The vibrationally elastic scattering of positrons from methane molecules is studied theoretically. The present theory is based on the fixed nuclei approximation. In order to properly consider the molecular symmetry, the wave function of scattered positron is expanded in terms of the symmetry adapted angular basis functions. The interaction potential between the positron and the CH4 molecule is represented in the form of a local potential which consists of the repulsive electrostatic and the attractive correlation polarization potentials. In the present calculation, the molecular orbital code GAMESS is employed to generate a multi centered target wave function. The Differential Cross Section (DCS) was calculated in the region of the collision energies from 1 to 10 eV. The shapes of the experimental DCSs are roughly reproduced by the present calculation throughout the collision energy, although the positions of the minima given by present calculation are rather different from those observed in the experimental data.

メタン分子による陽電子の振動的弾性散乱を理論的に研究した。この理論は固定核近似に基づいている。分子の対称性を適切に考慮するために、散乱された陽電子の波動関数は対称性を適応させた角度基底関数系で展開した。陽電子とメタン分子間の相互作用ポテンシャルは、斥力の静電的と引力の相関-分極ポテンシャルからなる局所ポテンシャルの形で表現される。今回の計算では、分子軌道コードGAMESSを採用して多中心標的波動関数を生成した。衝突エネルギーが1?10eVの範囲で、微分断面積を計算した。計算した全衝突エネルギー域で、実験による微分断面積の形が計算で再現できたが、極小の位置は実験データと異なっていた。