# Measurement of hyperfine splittings and isotope shifts in the $8p$ excited states of $^{205}$Tl and $^{203}$Tl using two-step laser spectroscopy

## TL;DR

This study employs two-step laser spectroscopy to precisely measure hyperfine splittings and isotope shifts in the $8p$ excited states of $^{203}$Tl and $^{205}$Tl, revealing discrepancies with previous data and confirming hyperfine anomalies.

## Contribution

It introduces a refined two-step laser spectroscopy method for hyperfine and isotope shift measurements in thallium isotopes, providing more accurate and consistent data.

## Key findings

- Hyperfine anomaly in $8p_{3/2}$ state confirmed
- Discrepancies found with earlier isotope shift measurements
- Enhanced frequency calibration technique used

## Abstract

A two-step, two-color laser spectroscopy technique has been used to measure the hyperfine splittings of the $8p$ excited states in $^{203}$Tl and $^{205}$Tl, as well as the $7s - 8p$ transition isotope shifts. For the case of the $8p_{3/2}$ state, our results show a hyperfine anomaly consistent with our recent measurements of other hyperfine splittings, and in disagreement with older results for this state. Our measurement of the $8p_{1/2}$ isotope shift is also in disagreement with earlier work. In this series of experiments, a UV laser was locked to the first-step transition and directed through a heated vapor cell, while a second spatially overlapping red laser was scanned across the two second-step transitions. To facilitate accurate frequency calibration, radio-frequency modulation of the second-step laser was used to create sidebands in the Doppler-free absorption spectrum.