Spectral measurements along the path of N ions impinged into dense He gas (400 Torr and 5.2 K). I. Emission spectra and decay measurements

Emission spectra and decay from 4 MeV/amu N-ion impinged dense helium gas (400 Torr, 5.2 K) were measured in a wavelength range from 3500 to 8000 A. Most emission peaks can be assigned to He excimers except for new triplet bands at 4599, 4587, and 4575 A. An excimer--dimer is proposed to interpret the triplet. All the emission bands have a fast initial-rise component which is completed within a N-ion pulse duration (2 ns). Emission peaks can be classified into two groups regarding their decays. Group I has a fast decay component with a lifetime of a few tens of nanoseconds and a very slow component corresponding to the afterglow. The fast decay component was explained as being caused by reproducing of the excimer by excimer--excimer reactions, analogous to the known reactions between the metastable a3(2ssigma 3Σ+/sub u/). On the other hand, group II has a much faster decay component of lifetime of a few nanoseconds and gives no afterglow. In this case, the regenerating reactions were negligible