On the paradigm

Structural characterization of the NO(X2Π)-N2O complex with mid-infrared laser absorption spectroscopy and quantum chemical calculations

Both positive and negative ions of N₃O₂ have been observed in various experiments. The neutral N₃O₂ was predicted to exist either as a weakly bound NO·N₂O complex or a covalent molecule. The rovibrational spectrum of the NO(X²Π)-N₂O complex has been measured for the first time in the 5.3 µm region using distributed quantum cascade lasers to probe the direct absorption in a slit-jet supersonic expansion. The observed spectrum is analyzed with a semi-rigid asymmetric rotor Hamiltonian for a planar open-shell complex, giving a bent geometry with an a-axis-NO angle of about 21.9°. The vibrationally averaged ²A'-²A″ energy separation is determined to be ε = 144.56(95) cm^-1 for the ground state, indicating that the electronic orbital angular momentum is partially quenched upon complexation. Geometry optimizations of the complex restricted to a planar configuration at the RCCSD(T)/aug-cc-pVTZ level of theory show that the ²A″ state is more stable than the ²A' state by about 110 cm^-1 and the N atom of NO points to the central N atom of N₂O at the minimum of the ²A″ state.

Kinetic stability and propellant performance of green energetic materials

A thorough theoretical investigation of four promising green energetic materials is presented. The kinetic stability of the dinitramide, trinitrogen dioxide, pentazole, and oxopentazole anions has been evaluated in the gas phase and in solution by using high-level ab initio and DFT calculations. Theoretical UV spectra, solid-state heats of formation, density, as well as propellant performance for the corresponding ammonium salts are reported. All calculated properties for dinitramide are in excellent agreement with experimental data. The stability of the trinitrogen dioxide anion is deemed sufficient to enable synthesis at low temperature, with a barrier for decomposition of approximately 27.5 kcal mol(-1) in solution. Oxopentazolate is expected to be approximately 1200 times more stable than pentazolate in solution, with a barrier exceeding 30 kcal mol(-1), which should enable handling at room temperature. All compounds are predicted to provide high specific impulses when combined with aluminum fuel and a polymeric binder, and rival or surpass the performance of a corresponding ammonium perchlorate based propellant. The investigated substances are also excellent monopropellant candidates. Further study and attempted synthesis of these materials is merited.

Further evidence for resonant photoelectron-solvent scattering in nitrous oxide cluster anions

The effects of anion solvation by N(2)O on photoelectron angular distributions are revisited in light of new photoelectron imaging results for the NO(-)(N(2)O)(n), n = 0-4 cluster anions at 266 nm. The new observations are examined in the context of the previous studies of O(-) and NO(-) anions solvated in the gas phase by nitrous oxide [Pichugin; et al. J. Chem. Phys. et al. 2008, 129, 044311.; Velarde; et al. J. Chem. Phys. et al. 2007, 127, 084302.]. The photoelectron angular distributions collected in the three separate studies are summarized and analyzed using bare O(-) and NO(-) as zero-solvation references. Solvent-induced deviations of the angular distributions from the zero-solvation reference are scaled by solvation number (n) to yield solvent-induced anisotropy differentials. These differentials, calculated identically for the O(-)(N(2)O)(n) and NO(-)(N(2)O)(n) cluster series, show remarkably similar energy dependences, peaking in the vicinity of a known electron-N(2)O scattering resonance. The results support the conclusion that the solvation effect on the photoelectron angular distributions in these cases is primarily due to resonant interaction of photoelectrons with the N(2)O solvent, rather than a solvent-induced perturbation of the parent-anion electronic wave function.