Calculation of total cross section and angular distribution of threshold and above-threshold ionization of atomic hydrogen at the fourth harmonic of aNd3+-glass laser

Computations have been made for various ionization processes of atomic hydrogen at 265 nm which correspond to the fourth harmonic of a ${\mathrm{Nd}}^{3+}$-glass laser. Both total and differential cross sections are reported for circular and linear polarization of photons. This is the first reported calculation to our knowledge of the differential cross sections of all processes from four- to ten-photon absorptions which correspond to above-threshold ionization, revealing certain characteristic new features.