Effective Dynamic Stabilization of Atomic Hydrogen in Strong Laser Fields

Huens, Etienne [UCL] Piraux, Bernard [UCL]

Two-photon ionization of atomic hydrogen is studied initially in the 2s-state using an intense ultrashort laser pulse. A physical mechanism that leads to effective dynamic stabilization of the atom is also described. This stabilization is the result of two distinct processes. In the tail of the pulse for low or moderate laser intensities, hydrogen is left in a coherent superposition of the initial state and in a set of p-Rydberg states, which leads to a substantial inhibition of ionization. At higher laser intensities, a second process becomes important, namely, transferring the population towards Rydberg states of higher angular momentum. This population migration occurs through degenerate nonresonant Raman coupling. This kind of stabilization occurs for pulse durations presently available for experimentation. These results are obtained using a spectral method and numerically solving the time-dependent Schrodinger equation.