# High-precision ab initio calculations of the spectrum of Lr$^{+}$

## TL;DR

This paper provides high-precision theoretical calculations of the electronic spectrum of Lr$^+$, aiding future experimental searches for optical resonances in lawrencium by offering accurate energy levels and transition data.

## Contribution

It introduces the first large-scale, systematic ab initio calculations of Lr$^+$ spectra using advanced relativistic methods, validated against the homologue Lu$^+$.

## Key findings

- Calculations closely match experimental data for Lu$^+$.
- Predicted energy levels for Lr$^+$ are expected to be highly accurate.
- Results will guide future experimental investigations of Lr$^+$.

## Abstract

The planned measurement of optical resonances in singly-ionised lawrencium (Z = 103) requires accurate theoretical predictions to narrow the search window. We present high-precision, ab initio calculations of the electronic spectra of Lr$^+$ and its lighter homologue lutetium (Z = 71). We have employed the state-of-the-art relativistic Fock space coupled cluster approach and the AMBiT CI+MBPT code to calculate atomic energy levels, g-factors, and transition amplitudes and branching-ratios. Our calculations are in close agreement with experimentally measured energy levels and transition strengths for the homologue Lu$^+$ , and are well-converged for Lr$^+$ , where we expect a similar level of accuracy. These results present the first large-scale, systematic calculations of Lr$^+$ and will serve to guide future experimental studies of this ion.