Semiclassical Calculations of Recurrence Spectra for Lithium Atoms in Parallel Electric and Magnetic Fields

By using region-splitting consistent and iterative method, we calculate the recurrence spectra of lithium atoms in parallel strong external electric and magnetic fields, and obtain the novel resonance structure in the photoabsorption spectrum above ionization threshold with a constant scaled electric field at F = 0.036, and a scaled energy at ε = 0.58 and ε = 0.006, respectively. The results are compared with those of hydrogen obtained by using standard closed orbit theory. It is demonstrated that the core-scattered effects exhibited in combination recurrence play a great role.