A chemical reaction between Sb and N2 was induced under high-pressure (32-35 GPa) and high-temperature (1600-2200 K) conditions, generated by a laser heated diamond anvil cell. The reaction product was identified by single crystal synchrotron X-ray diffraction at 35 GPa and room temperature as crystalline antimony nitride with Sb3N5 stoichiometry and structure belonging to orthorhombic space group Cmc21. Only Sb-N bonds are present in the covalent bonding framework, with two types of Sb atoms respectively forming SbN6 distorted octahedra and trigonal prisms and three types of N atoms forming NSb4 distorted tetrahedra and NSb3 trigonal pyramids. Taking into account two longer Sb-N distances, the SbN6 trigonal prisms can be depicted as SbN8 square antiprisms and the NSb3 trigonal pyramids as NSb4 distorted tetrahedra. The Sb3N5 structure can be described as an ordered stacking in the bc plane of bi-layers of SbN6 octahedra alternated to monolayers of SbN6 trigonal prisms (SbN8 square antiprisms). The discovery of Sb3N5 finally represents the long sought-after experimental evidence for Sb to form a crystalline nitride, providing new insights about fundamental aspects of pnictogens chemistry and opening new perspectives for the high-pressure chemistry of pnictogen nitrides and the synthesis an entire class of new materials.

Molecular dynamics calculations of inelastic collisions of atomic oxygen with molecular nitrogen are known to show orders of magnitude discrepancies with experimental results in the range from room temperature to many thousands of degrees Kelvin. In this work, we have achieved an unprecedented quantitative agreement with experiments even at low temperature, by including a non-adiabatic treatment involving vibronic states on newly developed potential energy surfaces. This result paves the way for the calculation of accurate and detailed databases of vibrational energy exchange rates for this collisional system. This is bound to have an impact on air plasma simulations under a wide range of conditions and on the development of Very Low Earth Orbit (VLEO) satellites, operating in the low thermosphere, objects of great technological interest due to their potential at a competitive cost.

The physics of vibrational kinetics in nitrogen-containing plasma produced by collisions with elec- trons is studied on the basis of recently derived cross sections and rate coefficients for the reso- nant vibrational-excitation by electron-impact. The temporal relaxation of the vibrational energy and of the vibrational distribution function is analyzed in a state-to-state approach. The electron and vibrational temperatures are varied in the range [0-50000] K. Conclusions are drawn with respect to the derivation of reduced models and to the accuracy of a relaxation time formalism. An analytical fit of the vibrational relaxation time is given.

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The vibrationally resolved partial ionization cross sections of the X, A and B states of N2+ in the photon energy range ~20-35 eV have been characterized by photoelectron spectroscopy. Vibrational intensity ratios of the X, A and B states have been determined. The vibrational intensity ratios of the X and B states show a wealth of both sharp and broad features. In accordance with previous experimental and theoretical studies, these structures have been assigned either to one-electron processes, like the interchannel coupling between the 3?g and 2?u ionization channels and the autoionization of excited Rydberg states, or to two-electron processes, like the recently observed non-Rydberg doubly excited resonances (NRDER). The present study provides direct information on the autoionization of the NRDER states and the experimental evidence of their predicted, but not yet verified, selective decay to the X, A and B states of N2+.