Two-photon above-threshold-ionization cross sections of rare-gas atoms by xuv photons

We have calculated the two-photon above-threshold-ionization cross sections of rare-gas atoms by extreme ultraviolet (xuv) photons in the extended framework of multichannel quantum defect theory. Since free-free dipole moments do not converge in the length gauge, we have made the combined use of the length gauge for small $r$ and the acceleration gauge for large $r$. The two-photon above-threshold ionization cross sections for Xe and Ar associated with the $p^5\left[{}^{2}P_{3∕2}\right]$ and $p^5\left[{}^{2}P_{1∕2}\right]$ ionic core states are calculated to be $1.0\times {10}^{-51}{\mathrm{cm}}^4\mathrm{s}$ and $2.0\times {10}^{-51}{\mathrm{cm}}^4\mathrm{s}$, respectively, for $25\text{‐}\mathrm{eV}$ photons.

Figure 1

MQDT description of the two-photon ATI process of Xe and Ar from the ground state.

Figure 2

Photoelectron angular distribution of the two-photon ATI of Xe by $25\text{‐}\mathrm{eV}$ photons.

Figure 3

Photoelectron angular distribution of the two-photon ATI of Ar by $25\text{‐}\mathrm{eV}$ photons.