Emission spectra from pulsed discharges in liquid helium

The time-resolved emission spectra from high-voltage pulsed discharges in liquid helium below 4.2 K, 1 atm, and cryogenic helium gas near 4.2 K, 1 atm, have been measured in the visible spectral range. In addition to the well known atomic lines, which exhibit strong and broadened profiles with continua at an early stage, some strong spectral features are observed near 23300 cm(-1) (similar to 430 nm) and 25500 cm(-1) (similar to 395 nm). The former can be assigned to He-2 transition (g(3) Sigma(g)(+) - a(3) Sigma(u)(+)), and the latter is not observed in previously reported works. These features disappear in 77 K and 300 K, 1 atm. He gas under the same experimental conditions.