The momentum distributions of triatomic molecular ion H₃²⁺ by intense laser pulses

We investigate theoretically the photoionization of triatomic molecular ion H-3(2+) by numerically solving the two-dimensional time-dependent Schrodinger equations under Bohn-Oppenheimer approximation. The results show that the photoelectron momentum distributions (PMDs) of H-3(2+) with different initial states are strongly dependent on the laser ellipticities and molecular orbital symmetry, and the PMDs of degenerate electronic states E-+/- are mirror images. Also, for degenerate electronic states E-+/-, vortex structures appear in the PMDs by the counter-rotating circularly polarized laser pulses as the time delay between the two pulses increases, which can be explained by multicenter ionization and ultrafast photoionization model.