We report a study of the intensity and time dependence of scintillation produced by weak $\alpha$-particle sources in superfluid helium in the presence of an electric field (0–45 kV/cm) in the temperature range of 0.2 to 1.1 K at the saturated vapor pressure. Both the prompt and the delayed components of the scintillation exhibit a reduction in intensity with the application of an electric field. The reduction in the intensity of the prompt component is well approximated by a linear dependence on the electric field strength with a reduction of 15$\%$ at 45 kV/cm. When analyzed using the Kramers theory of columnar recombination, this electric field dependence leads to the conclusion that roughly 40$\%$ of the scintillation results from species formed from atoms originally promoted to excited states and 60$\%$ from excimers created by ionization and subsequent recombination with the charges initially having a cylindrical Gaussian distribution about the $\alpha$ track of 60 nm radius. The intensity of the delayed component of the scintillation has a stronger dependence on the electric field strength and on temperature. The implications of these data on the mechanisms affecting scintillation in liquid helium are discussed.

• Received 3 October 2011

DOI:https://doi.org/10.1103/PhysRevA.85.042718