Anisotropy effects in methyl chloride ionization by metastable neon atoms at thermal energies

Quasiclassical trajectory calculations have been carried out for the Penning ionization reaction Ne*(P-3(2,0)) + CH3Cl --> CH3Cl+(X, A, B) + Ne + e(-). The calculations have been performed, within the rigid rotor approximation, for the translational energy range of 0.04-0.2 eV. The interaction potential of the colliding Ne*-CH3Cl system has been semiempirically estimated. The ionization probability has been determined, within the assumption that ionization occurs at the turning point, using a model which takes into account both geometry of the intermediate complex and ab initio electron density distribution of the orbitals involved on ionization. Calculations carried out for different rotational states (j = 0, 7, 14, 21, and 28, being j = 14 the most populated rotational level at 300 K) manifest the influence of CH3Cl rotation on partial (that is for specific X, A, B electronic states of CH3Cl+) and total ionization. Results averaged for the populated rotational levels at 300 K show that total ionization cross section decreases with translational energy. The branching ratio to X and A states also decreases, while that to the B state increases. These results fairly reproduce previous experimental results on the energy dependence total ionization cross section and branching ratios for the production of CH3Cl+, CH2Cl+, and CH3+ ions.