High-pressure transformation of N 2 ∕ O 2 mixtures into ionic compounds

We report the neutral-ionic transformation of ${\mathrm{N}}_{2}∕{\mathrm{O}}_{2}$ mixtures above $5\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ at $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The reaction is photoinduced with a Nd:YAG laser irradiation. The ionic compounds are characterized by Raman and infrared spectroscopic and synchrotron x-ray diffraction measurements. We show by Raman analysis that the $\mathrm{N}{\mathrm{O}}^{+}\mathrm{N}{\mathrm{O}}_{3}^{\ensuremath{-}}$ compound can trap a large fraction of ${\mathrm{O}}_{2}$ molecules, thus forming an ${\mathrm{O}}_{2}$ clathrate. But no ${\mathrm{N}}_{2}$ molecule can be included in this nitrosonium nitrate compound. We propose an orthorhombic unit cell with 10 $\mathrm{N}{\mathrm{O}}^{+}\mathrm{N}{\mathrm{O}}_{3}^{\ensuremath{-}}$ in it.