  The study of proportional electroluminescence in two-phase argon is relevant
in the field of noble-gas liquid detectors for dark matter search and
low-energy neutrino experiments. In this work, we continued to study
proportional electroluminescence (EL) in two-phase argon doped with a minor (9
ppm) admixture of nitrogen, in the VUV, UV and visible spectral ranges. We
confirmed the effect of enhancement of the EL yield, as well as the presence of
non-VUV component in addition to that of VUV, in proportional
electroluminescence in two-phase Ar. On the other hand, the contribution of
non-VUV component determined here within the model of N2 emission in the UV,
turned out to be insufficient to explain the EL yield enhancement effect.
Accordingly, the problem of proportional electroluminescence in two-phase Ar
remains unresolved.
