Photodetachment of H⁻ in Inhomogeneous Electric and Magnetic Fields

In this paper, we investigate the photodetachment of H- in parallel-gradient electric and magnetic fields on the basis of a semiclassical closed-orbit theory. Firstly, we give a clear physical picture of a detached electron's movement in parallel-gradient electric and magnetic fields. Then we derive the analytical formula for the photodetachment cross section of this system. It is found that parallel gradient electric and magnetic fields can produce some interesting effects. Aside from the closed orbits previously reported for the photodetachment of H- in a parallel-gradient electric field, some additional closed orbits are produced owing to the effect of the magnetic field. Compared with the cross section of H- in a gradient electric field, the oscillation in the cross section of our system becomes much more complicated. Moreover, our study shows that the oscillation amplitude in the photodetachment cross section sensitively depends on the electric field gradient and external field strength. In this study, we provide a new understanding of the photodetachment of negative ions in the presence of inhomogeneous electric and magnetic fields.