Role of Electron Bubbles on Laser Induced Breakdown in LiquidHe4

Recent experimental results on laser-induced breakdown of liquid ${\mathrm{He}}^4$ have been interpreted by assuming that unbound electrons collide mainly with thermal rotons between the $\lambda$ temperature and 1.5°K. Previous experimental results on the behavior of hot electrons injected into liquid helium suggest that the collision frequency $\nu$ of the unbound electrons and their lifetime $\tau$ before they are trapped into bubbles are relatively temperature-independent between 4.2 and 1.35°K in contrast to the above-mentioned assumption. An alternative explanation is offered to the recent results based on an assumed temperature-dependent ejection of electrons from the bubbles.