Electron thermalization length in solid para-hydrogen at low-temperature

We report the first ever measurements of the thermalization length of low-energy electrons injected into solid para-hydrogen at a temperature T approximate to 2.8 K. The use of the pulsed Townsend photoinjection technique has allowed us to investigate the behavior of quasi-free electrons rather than of massive, slow negative charges, as reported in all previous literature. We have found an average thermalization length < z(0)> = 26.1 nm, which is three to five times longer than that in liquid helium at the same temperature.