Liquid and solid argon, and nitrogen-doped liquid and solid argon scintillators

Abstract

The scintillation decay of nitrogen-doped liquid and solid argon excited by 207Bi internal conversion electrons has been studied by a single-photon counting technique. Two exponential decays are observed for [N2] < 103 ppm in liquid and solid, which result from transition Ar2★(3Σu+) → 2Ar + hν(uv) and Ar2★(3Σu+) → 2Ar + hν(uv). The Ar2★(3Σu+) state are quenched by doped nitrogen in liquid argon but not in the solid phase for [N2] < 500 ppm. The scintillation intensity excited by alpha particle decreases with increasing [N2]. The second positive emission N2★(C3Πu) → N2★(B3Πg) + hν (visible) which is the main emission in an argon-nitrogen gas scintillator, has not bbeen observed for 5 ppm ⪅ [N2] ⪅ 13% nitrogen in liquid or solid argon.