Multiphoton detachment of negative ions in an intense radiation field

We have applied a momentum-space method to the solution of the three-dimensional time-dependent Schrödinger equation for electron detachment from a model negative ion, in particular ${\mathrm{H}}^{\mathrm{-}}$. We have studied such phenomena as excess-photon detachment and threshold effects. For selected cases, we obtain excellent agreement with the Floquet calculations. We also present results in regimes of strong interest to experimental efforts.