# High-resolution spectroscopy of gaseous $^\mathrm{83m}$Kr conversion electrons with the KATRIN experiment

## TL;DR

This paper reports the first high-resolution spectroscopic measurements of gaseous $^{83m}$Kr conversion electrons using the KATRIN experiment, marking a key milestone for neutrino mass measurement calibration.

## Contribution

It demonstrates the full KATRIN beamline's capabilities and achieves unprecedented precision in measuring conversion electron line widths from $^{83m}$Kr decay.

## Key findings

- Successful calibration measurement with KATRIN
- Determined line widths with ~1% precision
- Validated KATRIN's energy resolution of ~1 eV

## Abstract

In this work, we present the first spectroscopic measurements of conversion electrons originating from the decay of metastable gaseous $^\mathrm{83m}$Kr with the Karlsruhe Tritium Neutrino (KATRIN) experiment. The results obtained in this calibration measurement represent a major commissioning milestone for the upcoming direct neutrino mass measurement with KATRIN. The successful campaign demonstrates the functionalities of the full KATRIN beamline. The KATRIN main spectrometer's excellent energy resolution of ~ 1 eV made it possible to determine the narrow K-32 and L$_3$-32 conversion electron line widths with an unprecedented precision of ~ 1 %.