Spontaneous optical flashes in proton-irradiated solid deuterium

Samples of solid deuterium, cooled below 4.2 K, and irradiated by 15 MeV protons, will spontaneously flash. The flash-spectrum occurs in the near infrared with a maximum close to 920 nm. The flash intensity is two to three orders of magnitude greater than a steady-state emission observed in the same spectral region. The flash frequency is 1 every 1 to 3 min after several hours of irradiation of 10 nA/cm2. Heat pulses have been detected accompanying many of the flashes and both can be stimulated by the application of external heat triggers. Following the optical flash, the steady-state emission intensity decreases by an amount that is wavelength dependent. While it is thought that these flashes are caused by atomic association in the solid, the species responsible for the optical emission is uncertain as is the transition itself.