Direct momentum-space calculations for the resonant multiphoton processes of a hydrogen atom under intense laser pulses

Lande subtraction method with finite integration limits and application to strong-field problems

The Lande subtraction method has been widely used in Coulomb problems, but the momentum coordinate p∈(0,∞) is assumed. In past applications, a very large range of p was used for accuracy. We derive the supplementary formulation with p∈(0,p_{max}) at reasonably small p_{max} for practical calculations. With the recipe, accuracy of the hydrogenic eigenspectrum is dramatically improved compared to the ordinary Lande formula by the same momentum grids. We apply the present formulation to strong-field atomic above-threshold ionization and high-order harmonic generations. We demonstrate that the proposed momentum space method can be another practical theoretical tool for atomic strong-field problems in addition to the existing methods.