Dynamic stabilization of Na atom in an intense pulsed laser field

We investigate theoretically the ionization properties of the valence electron for the alkali metal atom Na in an intense pulsed laser field by solving numerically the time-dependent Schr ¨odinger equation with an accurate l-dependent model potential.By calculating the variations of the ionization probabilities with laser peak intensity for wavelengths ranging from 200 nm to 600 nm,our results present a dynamic stabilization trend for the Na atom initially in its ground state(3 s) and the excited states(3 p and 4 s) exposed to an intense pulsed laser field.Especially a clear "window" of dynamic stabilization at lower laser intensities and longer wavelengths for the initial state 4 s(the second excited state) is found.By analyzing the time-dependent population distributions of the valence electron in the bound states with the different values of principal quantum number n and orbital quantum number l,we can attribute the dynamic stabilization to the periodic population in the low-excited states since the valence electron oscillates rapidly between the lowly excited states and the continuum states.