Red Emission from Pulse Irradiated H2 O Ice

Luminescence was emitted in the 600-800 nm region by crystalline ice irradiated with pulsed 0.53 MeV electrons at 88 K. Superimposed on a broad continuum which decreased to long wavelengths was a narrow (Δλ < 0.5 nm) Balmer α emission from atomic hydrogen at 656.25 nm and a weaker, less resolved (Δλ < 2 nm) peak at 778 nm which was probably due to the $3p^{5}P\rightarrow 3s^{5}S^{0}$ transition of atomic oxygen. The Balmer α emission was formed with a radiolytic yield of $9.7\times 10^{-7}$ photons/100 eV, and, unlike the continuum emission, it decreased in intensity with decreasing crystallite size. The Balmer α emission decayed according to second-order kinetics.