Charge-transfer processes in collisions of slow H+ ions with hydrocarbon molecules: CN4, C2H2, C2H6, and C3H8 - art. no. 062715

Charge-transfer processes in collisions of H+ ions with CH4, C2H2, C2H6, an d C3H8 molecules have been studied based on joint experimental and theoreti cal approaches in the collision energy from 0.2 to 4.0 keV. In the present experiment, the initial growth rate method was employed for determination o f cross sections, while in the present theory, the molecular orbital expans ion method was utilized for CH4 and C2H2 molecules. Both experimental and t heoretical results indicate that if one assumes vibrationally excited molec ular ions (CH4+, C2H2+, C2H6+, and C3H8+) in the exit channel, then charge- transfer processes are sometimes found to become more favorable due to an a ccidental resonant condition. This is the clear indication of the role of v ibrational excited states for charge transfer, and is found to be particula rly so as the molecular size increases.