# Electron Correlation in the Lanthanides: $4f^2$ spectrum of Ce$^{2+}$

## TL;DR

This paper investigates electron correlation effects in lanthanide ions, specifically Ce$^{2+}$ with a $4f^2$ configuration, using advanced multireference methods to improve atomic property predictions.

## Contribution

It introduces an effective approach for calculating wave functions in lanthanides, emphasizing the importance of higher-order methods for accuracy.

## Key findings

- Electron correlation significantly affects lanthanide spectra.
- Multireference methods improve prediction accuracy.
- Higher-order methods yield more reliable results.

## Abstract

Atoms and ions of Lanthanides have multiple opens shells along with an open $4f^k$ subshell. This paper studies the effect of electron correlation in such systems and how wave functions can be determined for the accurate prediction of atomic properties in the case of Ce$^{2+}$ where $k=2$, using the multireference single- and double-excitation method. An efficient higher-order method is recommended for more reliable results.