# Frequency measurement of the clock transition of an indium ion sympathetically-cooled in a linear trap

## TL;DR

This paper reports a precise measurement of the indium ion's clock transition frequency using sympathetic cooling with calcium ions in a linear trap, enhancing accuracy in optical frequency standards.

## Contribution

It introduces a method for measuring the indium ion's clock transition frequency with high precision using sympathetic cooling and optical frequency comb referencing.

## Key findings

- Frequency measured as 1,267,402,452,901,049.9 Hz
- Achieved measurement uncertainty of 6.9 Hz
- Demonstrated effective sympathetic cooling in a linear rf trap

## Abstract

We report frequency measurement of the clock transition in an 115In+ ion sympathetically-cooled with Ca+ ions in a linear rf trap. The Ca+ ions are used as a probe of the external electromagnetic field and as the coolant for preparing the cold In+. The frequency is determined to be 1 267 402 452 901 049.9 (6.9) Hz by averaging 36 measurements using an optical frequency comb referenced to the frequency standards located in the same site.