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

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Abstract
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 Å. Most emission peaks can be assigned to He excimers except for new triplet bands at 4599, 4587, and 4575 Å. 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(2sσ 3Σ+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.