  The dependence on applied electric field ($0 - 40$ kV/cm) of the
scintillation light produced by fast electrons and $\alpha$ particles stopped
in liquid helium in the temperature range of 0.44 K to 3.12 K is reported. For
both types of particles, the reduction in the intensity of the scintillation
signal due to the applied field exhibits an apparent temperature dependence.
Using an approximate solution of the Debye-Smoluchowski equation, we show that
the apparent temperature dependence for electrons can be explained by the time
required for geminate pairs to recombine relative to the detector signal
integration time. This finding indicates that the spatial distribution of
secondary electrons with respect to their geminate partners possesses a heavy,
non-Gaussian tail at larger separations, and has a dependence on the energy of
the primary ionization electron. We discuss the potential application of this
result to pulse shape analysis for particle detection and discrimination.
