# Ionization spectra of highly Stark shifted rubidium Rydberg states

## TL;DR

This paper combines experimental measurements and numerical calculations to analyze ionization spectra of highly Stark-shifted rubidium Rydberg states, demonstrating good agreement and advancing understanding of their ionization behavior under strong electric fields.

## Contribution

It introduces a simplified numerical method using a complex absorbing potential with minimal free parameters and provides experimental validation for high principal quantum number Rydberg states.

## Key findings

- Good agreement between experimental and numerical spectra
- Effective reduction of free parameters in calculations
- Observation of ionization spectra at high electric fields

## Abstract

We report on the observation and numerical calculation of ionization spectra of highly Stark-shifted Rydberg states of rubidium beyond the classical ionization threshold. In the numerical calculations, a complex absorbing potential (CAP) allows us to predict the energy levels and ionization rates of Rydberg states in this regime. Our approach of adjusting the CAP to the external electric field reduces the number of free parameters from one per resonance to a single one. Furthermore, we have measured the ionization spectra of magneto-optically trapped rubidium atoms which are excited to principal quantum numbers of 43 and 70 at various electric fields. The emerging ions are detected using an ion optics. We find good agreement between the numerically and experimentally obtained spectra.