Polarization degrees for 3p 2P3/2-3s 2S1/2 transition of C3+ (1s23p) produced in collisions of C4+ with He and H2

Charge transfer processes in collisions of C4+ with ground-state He and H2 are investigated using the two-center atomic orbital close-coupling method. Total and state-selective single-electron capture cross sections are obtained for collision energies between 1 and 7 keV/amu, and comparison with available experimental data reveals a good agreement. The polarization degrees for the 3p 2P3/2-3s 2S1/2 transition of C3+(3p 2P3/2) are calculated from the magnetic substate-selective cross sections, in which the cascade effects are also included. The polarization degree in the C4+ + H2 collisions varies smoothly in the considered energy region and generally agrees with the experimental measurements, while if appears minimum at a collision energy of 2 keV/u for C4+ + He collisions. By studying the time-evolution of electron capture dynamics in the two systems we have found that the polarization difference between the two systems is caused mainly by interactions at relatively small internuclear distances, and then modified by the Stark effect of target ions. (author)