Photodetachment of H- from intense, short, high-frequency pulses

We study the photodetachment of an electron from the hydrogen anion due to short, high-frequency laser pulses by numerically solving the time-dependent Schrodinger equation. Simulations are performed to investigate the dependence of the photoelectron spectra on the duration, chirp, and intensity of the pulses. Specifically, we concentrate on the low-energy distributions in the spectra that result from the Raman transitions of the broadband pulses. Contrary to one-photon ionization, the low-energy distribution maintains an almost constant width as the laser bandwidth is expanded by chirping the pulses. In addition, we study the transitions of the ionization dynamics from the perturbative to the strong-field regime. At high intensities, the positions of the net one- and two-photon absorption peaks in the spectrum shift and the peaks split to multiple subpeaks due to multiphoton effects. Moreover, although the one- and two-photon peaks and low-energy distribution exhibit saturation of the ionization yields, the low-energy distribution shows relatively mild saturation.