Velocity dependence of the ionization cross section of methyl chloride molecules ionized by metastable argon atoms

The ionization of methyl chloride molecules by metastable argon atom collis ions is studied in a crossed beam experiment. The relative cross sections e xhibit a decreasing trend in the investigated collision energy range, 0.04- 0.3 eV. The results have been analyzed in terms of the potential energy int eraction between the two colliding partners, using the optical potential mo del. The effect of the potential energy anisotropy has also been investigat ed by the use of a simple sudden approximation within the semiclassical fra mework. The experimental cross-sections appear to be rather well reproduced by the theoretical calculation with a spherically average potential and ve ry close to the calculation performed using the potential for a perpendicul ar orientation between the C-Cl axis and the approaching direction of the e xcited atom.