# Zero-phonon lines in the spectra of dysprosium atoms in superfluid helium

## TL;DR

This study investigates the zero-phonon line in the absorption spectrum of dysprosium atoms in superfluid helium, revealing temperature-dependent broadening due to phonon scattering and a significantly increased intrinsic spectral width.

## Contribution

The paper provides the first experimental observation of ZPL broadening in Dy atoms within superfluid helium and links it to phonon scattering effects and rapid quenching mechanisms.

## Key findings

- Temperature-dependent ZPL broadening observed
- Intrinsic spectral width is 2300 times larger than free atom linewidth
- Fast radiationless quenching of the excited state identified

## Abstract

We present an experimental study of a zero-phonon line (ZPL) in the absorption spectrum of Dy atoms solvated in superfluid He. The dopants reside in nanometer-sized spherical cavities known as atomic bubbles. We observe a temperature-dependent broadening of ZPL in the absorption spectrum. The effect is attributed to the scattering of thermal phonons on the atomic bubble that leads to the dephasing of the Dy transition dipole. The extrapolated ZPL intrinsic spectral width at zero temperature is 2300 times larger than the natural linewidth in a free atom. This can be assigned to a fast radiationless quenching of the upper state of the studied transition.