Rydberg state creation by tunnel ionization

Abstract

It is well known from numerical and experimental results that the fraction of Rydberg states (excited neutral atoms) created by tunnel ionization declines dramatically with increasing ellipticity of laser light, in a way that is similar to high harmonic generation (HHG). We present a method to analyze this dependence on ellipticity, deriving a probability distribution of Rydberg states that agrees closely with experimental (Nubbemeyer et al 2008 Phys. Rev. Lett. 101 233001) and numerical results. We show using analysis and numerics that most Rydberg electrons are ionized before the peak of the electric field and therefore do not come back to the parent ion. Our work shows, for the first time, the similarities and differences in the process that distinguishes formation of Rydberg electrons from electrons involved in HHG: ionization occurs in a different part of the laser cycle, but the post-ionization dynamics are very similar in both cases, explaining why the same dependence on ellipticity is observed.

Photoelectron spectra and high Rydberg states of lithium generated by intense lasers in the over-the-barrier ionization regime

“…The reason is similar to the observation that Freeman resonances are not formed in photoelectron spectra if circularly polarized IR lasers are used; see Bucksbaum et al [52]. Finally, the ellipticity dependence of Rydberg state formation reported in Nubbemeyer et al [36] has been explained recently by Landsman et al [47] using semiclassical simulation. They found that these Rydberg atoms are formed by electrons ionized before the peak of the laser field and that rescattering does not play any role.…”

“…In the RS model, the Rydberg states are formed by recombination of the returning electrons with the ion, at the end of the laser pulse. The RS model does not have to deal with Q2, but this model has been refuted [41,47], since a recombination would have to involve the emission of radiation which was not considered in the RS model according to [36,46]. In the IS model, Rydberg states are formed in the early part of the laser pulse (Q1); the survival of Rydberg states in the laser field (Q2) is explained (or modeled) by destructive interference of -type Raman transitions via the continuum states.…”

Interpreting electron-momentum distributions and nonadiabaticity in strong-field ionization

“…Clouds of 300 000 electrons simulated the ionized part of the wave function. For ellipticities <0.2, many electrons rescatter close to the parent ion [28], and quantum mechanical effects are expected to become important. Since these cannot be described in a classical framework, simulations were only performed for 0.2, and trajectories coming closer than 5 a.u.…”

Dependence of Rydberg Yield on Ellipticity in Strong Field Ionization

“…(1). The overall structure of the derivation of Rydberg yield is (see [4] for more detail): We show that the electrons end up far from the exit point, x e , after the laser pulse has passed. This imposes a zero a e-mail: landsmaa@phys.ethz.ch This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.…”

“…This bifurcation can be explained as resulting from the interaction of the drift momentum of the electron and the Coulomb correction. The value of the bifurcation was shown analytically to approximately coincide with the point where the drift velocity cancels the Coulomb correction [4].…”