Nucleation, solvation and boiling of helium excimer clusters

TL;DR

This study investigates helium excimer clusters' formation, solvation, and boiling in helium's gas and liquid phases, revealing phase coexistence and cluster behavior through fluorescence spectroscopy under varying temperature and pressure.

Contribution

It provides new insights into the nucleation, solvation, and boiling processes of helium excimer clusters using fluorescence spectroscopy across different phases and conditions.

Findings

Identification of phase coexistence and separation of excimer-helium mixtures.

Pressure-dependent merging of rotational lines indicating cluster behavior.

Detailed understanding of nucleation and boiling of He$_2^*$-He$_n$ clusters.

Abstract

Helium excimers generated by a corona discharge were investigated in the gas and normal liquid phases of helium as a function of temperature and pressure between 3.8 and 5.0 K and 0.2 and 5.6 bar. Intense fluorescence in the visible region showed the rotationally resolved $d^3\Sigma_u^+ \rightarrow b^3\Pi_g$ transition of He$_2^*$. With increasing pressure, the rotational lines merged into single features. The observed pressure dependence of linewidths, shapes and lineshifts established phases of coexistence and separation of excimer-helium mixtures, providing detailed insight into nucleation, solvation and boiling of He$_2^*$-He$_n$ clusters.