Nucleation, solvation and boiling of helium excimer 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 $d^3{\Sigma }_u^{+}\to b^3{\Pi }_g$ transition of He${}_2^{\ast }$. 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${}_2^{\ast }$-He${}_n$ clusters.

5 pages, 5 figures