Laser-assisted positronium formation in positron collisions with Rydberg hydrogen

We investigate the formation of positronium (Ps) in the presence of a linearly polarized infrared laser field, via the collision of positrons with Rydberg hydrogen atoms $\mathrm{H}({n}_{\mathrm{H}})$ where ${n}_{\mathrm{H}}$ is the principal quantum number. We are using the classical trajectory Monte Carlo method (CTMC) which is justified for ${n}_{\mathrm{H}}\ensuremath{\ge}3$. The hydrogen in excited states has an effective dipole moment which in the presence of a laser field leads to a dipolar focusing [H. B. Ambalampitiya et al., J. Phys. B: At. Mol. Opt. Phys. 57, 10LT01 (2024)]. Due to this effect, the Ps formation cross section is enhanced substantially as compared to the zero-field case. The degree of this enhancement is controlled by the positron velocity, laser frequency, and laser-field amplitude. The final-state distribution in Ps is much broader than in the zero-field case.