Electronic excitation by short X-ray pulses: From quantum beats to wave packet revivals

TL;DR

This paper introduces a straightforward method to accurately determine wave packet periodicities in quantum systems from energy differences, enhancing understanding of phase shifts and revivals especially in low quantum number regimes.

Contribution

It presents a new approach to directly calculate classical periods and revival times from energy differences, improving accuracy over traditional methods for low n states.

Findings

More accurate period and revival time calculations for low n states.

Clarification of phase shift origins in wave packet maxima.

Application to highly charged ions excited by short X-ray pulses.

Abstract

We propose a simple way to determine the periodicities of wave packets in quantum systems directly from the energy differences of the states involved. The resulting classical periods and revival times are more accurate than those obtained with the traditional expansion of the energies about the central quantum number n, especially when n is low. The latter type of wave packet motion occurs upon excitation of highly charged ions with short XUV or X-ray pulses. Moreover, we formulate the wave packet dynamics in such a form that it directly reveals the origin of phase shifts in the maxima of the autocorrelation function. This phenomenon, so far poorly understood since it is not prominent in the high n regime, becomes a dominant feature in low n wave packet dynamics.