Surface location of sodium atoms attached to He-3 nanodroplets

TL;DR

This study combines experimental laser spectroscopy and density functional theory calculations to determine that sodium atoms attach to the surface of helium-3 nanodroplets, forming a dimple structure similar to that on helium-4 droplets.

Contribution

It provides the first combined experimental and theoretical evidence for the surface location of sodium on helium-3 nanodroplets, including a microscopic description of the dimple.

Findings

Sodium atoms reside on the surface of helium-3 droplets.

Spectroscopic data are similar for Na on helium-3 and helium-4 droplets.

Density functional calculations support the surface attachment and describe the dimple structure.

Abstract

We have experimentally studied the electronic $3p\leftarrow 3s$ excitation of Na atoms attached to $^3$He droplets by means of laser-induced fluorescence as well as beam depletion spectroscopy. From the similarities of the spectra (width/shift of absorption lines) with these of Na on $^4$He droplets, we conclude that sodium atoms reside in a ``dimple'' on the droplet surface. The experimental results are supported by Density Functional calculations at zero temperature, which confirm the surface location of sodium on $^3$He droplets, and provide a microscopic description of the ``dimple'' structure.