Relativistic effects in photoionizing a circular Rydberg state in the optical regime

Abstract

We study the photoionization process of a hydrogen atom initially prepared in a circular Rydberg state. The atom is exposed to a two-cycle laser pulse with a central wavelength of 800 nm. Before the atom approaches saturation, at field intensities of the order of 10 17 W/cm 2 , relativistic corrections to the ionization probability are clearly seen. The ionization is predominantly driven by the radiation pressure in the propagation direction of the laser field, not by the electric field. Direct comparisons with the full numerical solution of the time-dependent Dirac equation demonstrate quantitative agreement with a semirelativistic approximation, which is considerably easier to implement.

Relativistic photoionization with elliptically polarized laser fields in the ultraviolet region

“…The relativistic correction is seen to be negative for all intensities studied here. This is in agreement with previous works [12,22,24], and it can be understood from the fact that the increased inertia acquired by the electron renders it slightly more stable against ionization.…”

“…As mentioned, the semi-relativistic approach has previously been tested by direct comparison with solutions of the Dirac equation for cases involving linear polarization [12,22,23]. We will here demonstrate its adequacy for elliptic polarization.…”

“…(40). For linearly polarized fields, the leading order term, q 2 /2µ, has proven sufficient in calculations pertaining to both the ultra violet [12] and the optical regions [22]. Another work with fields in the X-ray regime, however, demonstrated the need for also including the term proportional to q 4 [23].…”