Physical and chemical effects on crystalline H₂ O₂ induced by 20 keV protons

We present laboratory studies on radiation chemistry, sputtering, and amorphization of crystalline H₂ O₂ induced by 20 keV protons at 80 K. We used infrared spectroscopy to identify H₂ O, O₃, and possibly HO₃, measure the fluence dependence of the fraction of crystalline and amorphous H₂ O₂ and of the production of H2 O and destruction of H₂ O₂. Furthermore, using complementary techniques, we observe that the sputtering yield depends on fluence due to the buildup of O₂ radiation products in the sample. In addition, we find that the effective cross sections for the destruction of hydrogen peroxide and the production of water are very high compared to radiation chemical processes in water even though the fluence dependence of amorphization is nearly the same for the two materials. This result is consistent with a model of fast cooling of a liquid track produced by each projectile ion rather than with the disorder produced by the formation of radiolytic products.