Quantum dynamics of atomic Rydberg excitation in strong laser fields.

Shilin Hu,Weidong Li,Hang Lv,Dajun Ding,Wilhelm Becker,Mingqing Liu,Haifeng Xu,Tianxiang Yang,Mingxing Jin,Xiaolei Hao,Qianguang Li,Jing Chen

doi:10.1364/oe.27.031629

Abstract

Neutral atoms have been observed to survive intense laser pulses in high Rydberg states with surprisingly large probability. Only with this Rydberg-state excitation (RSE) included is the picture of intense-laser-atom interaction complete. Various mechanisms have been proposed to explain the underlying physics. However, neither one can explain all the features observed in experiments and in time-dependent Schrödinger equation (TDSE) simulations. Here we propose a fully quantum-mechanical model based on the strong-field approximation (SFA). It well reproduces the intensity dependence of RSE obtained by the TDSE, which exhibits a series of modulated peaks. They are due to recapture of the liberated electron and the fact that the pertinent probability strongly depends on the position and the parity of the Rydberg state. We also present measurements of RSE in xenon at 800 nm, which display the peak structure consistent with the calculations.

Highlights

In strong-field atomic and molecular physics, Rydberg states attracted much attention in the 1990s [1–4] but thereafter have been ignored for a long time
Owing to the presence of the attractive Coulomb field of the ion, the electron may be left with negative energy at the end of the laser pulse, which corresponds to capture into a Rydberg state [8], known as frustrated tunneling ionization (FTI) [9]
Populations of Rydberg states with even or odd parity versus laser intensity calculated via time-dependent Schrodinger equation (TDSE) (a) and the quantum model (QM)(b) for an initial 1s state

Summary

Introduction

In strong-field atomic and molecular physics, Rydberg states attracted much attention in the 1990s [1–4] but thereafter have been ignored for a long time This is because, in an intense laser field, the atoms or molecules are so strongly disturbed that the electrons already in the ground state of the neutral atom or even the ion can be liberated very efficiently [5–7]. Our quantum model well reproduces all the features observed in a TDSE simulation, including the dependence on the parities of the initial and final states and the just-mentioned fact that the peaks in the RSE intensity dependence alternate in height. Our work provides a quantum picture of RSE in intense laser fields: first, the electron is pumped by the laser field into a continuum state

Methods

Results

Conclusion