# Study of even-parity Rydberg and autoionizing states of lutetium by laser resonance ionization spectroscopy

## TL;DR

This study used laser resonance ionization spectroscopy to identify and analyze even-parity Rydberg and autoionizing states of lutetium, revealing new levels and comparing results with previous research.

## Contribution

It reports new Rydberg and autoionizing state levels of lutetium and applies relativistic multichannel theory for state assignment, advancing spectroscopic knowledge of lutetium.

## Key findings

- Identified 51 new levels in the $6s^2nd$ $^2D_{5/2}$ series.
- Identified 52 new levels in the $6s^2ns$ $^2S_{1/2}$ series.
- Observed six autoionization series converging to specific ionic states.

## Abstract

Multi-step laser resonance ionization spectroscopy of lutetium (Lu) has been performed at TRIUMF's off-line laser ion source test stand. The even-parity Rydberg series $6s^2nd$ $^2D_{3/2}$, $6s^2nd$ $^2D_{5/2}$ and $6s^2ns$ $^2S_{1/2}$ were observed converging to the 6s$^2$ ionization potential. The experimental results has been compared to previous work. 51 levels of Rydberg series $6s^2nd$ $^2D_{5/2}$ and 52 levels of Rydberg series $6s^2ns$ $^2S_{1/2}$ were reported new. Additionally six even-parity autoionization (AI) series converging to Lu ionic states $5d6s$ $^3D_1$ and $5d6s$ $^3D_2$ were observed. The level energies of these AI states were measured. The configurations of the AI states were assigned by relativistic multichannel theory (RMCT) within the framework of multichannel quantum defect theory (MQDT).