Emission spectroscopy of solid nitrogen Elena Savchenko a, * , Ivan Khyzhniy a , Sergey Uyutnov a , Mikhail Bludov a , Galina Gumenchuk b , Vladimir Bondybey b a Institute for Low Temperature Physics & Engineering, NASU, Kharkiv 61103, Ukraine b Lehrstuhl für Physikalische Chemie II TUM, Garching b. München 85747, Germany highlights  Radiation effects in solid N 2 were studied by optical and current emission spectroscopy.  Cathodoluminescence and yields of TSL, NsL, PSL, TSEE, PSEE were measured.  Analysis of products of the electron-ion recombination reactions was performed.  New evidences of hole self-trapping with the cation N þ 4 formation were obtained.  “Fingerprints” of N  3 species were detected by the PSEE. article info Article history: Received 27 October 2015 Received in revised form 21 December 2015 Accepted 30 December 2015 Available online xxx Keywords: Thermally stimulated luminescence Thermally stimulated exoelectron emission Photon-stimulated luminescence Photon-stimulated exoelectron emission Self-trapped holes Solid nitrogen abstract Monitoring of the cathodoluminescence spectra temporal evolution and concurrent measurements of optical and current relaxation emissions revealed stabilization and accumulation of the radiation- induced charged species. New results in favor of hole self-trapping with the tetranitrogen cation N þ 4 formation are presented. “Fingerprints” of N  3 species are detected by the photon-stimulated exoelectron emission. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Nitrogen solids known for their bright luminescence gained general recognition as model molecular crystals. Interest in the research of these solids is associated with the prospect of their application as high energy-density materials (Nguyen, 2003; Zarko, 2010), their use as moderators (Ghandi and Miyake, 2011) and as matrices in radiation chemistry (Grigoriev and Trakhtenberg,1996). Investigations of nitrogen emission spectra were undertaken to ascertain the polar light nature (Kragh, 2010). These solids also attract much attention in astrophysical research because solid ni- trogen and nitrogen-containing “ices” are present in cosmic space (Clark et al., 2012). In all these fields of science radiation effects, energy storage, transformation and its release are the focus of studies. Until ricently radiation effects in solid N 2 were studied and discussed mostly in terms of neutral electronic excitations. The formation of N radicals in solid nitrogen grown from discharge or irradiated with an electron beam was detected in the first studies related to clearing up elements involved in polar light (Vegard, 1924; McLennan and Shrum, 1924). Later studies, e.g. (Bass and Broida, 1956; Oehler et al., 1977) revealed an interaction of N rad- icals with the surroundings. The laboratory studies of asrophysical “ices” detected the azid radical N 3 in solid nitrogen pre-irradiated by protons (Hudson and Moore, 2002), electrons (Jamieson and Kaiser, 2007) and synchrotron radiation (Wu et al., 2012). Despite a long history of solid N 2 spectroscopy the problem of charged (ionic) species generation, stability and their reactions is only beginning to be studied. The method of activation * Corresponding author. E-mail address: elena.savchenko@mytum.de (E. Savchenko). Contents lists available at ScienceDirect Radiation Measurements journal homepage: www.elsevier.com/locate/radmeas http://dx.doi.org/10.1016/j.radmeas.2015.12.044 1350-4487/© 2016 Elsevier Ltd. All rights reserved. Radiation Measurements xxx (2016) 1e5 Please cite this article in press as: Savchenko, E., et al., Emission spectroscopy of solid nitrogen, Radiation Measurements (2016), http:// dx.doi.org/10.1016/j.radmeas.2015.12.044