Deuterium fractionation of nitrogen hydrides: detections of NHD and ND2

ABSTRACT Although ammonia is an abundant molecule commonly observed towards the dense interstellar medium, it has not yet been established whether its main formation route is from gas-phase ion–molecule reactions or grain-surface hydrogen additions on adsorbed nitrogen atoms. Deuterium fractionation can be used as a tool to constrain formation mechanisms. High abundances of deuterated molecules are routinely observed in the dense interstellar medium, with the ratio between deuterated molecules and the main isotopologue enhanced by several orders of magnitude with respect to the elemental D/H ratio. In the case of ammonia, the detection of its triply deuterated isotopologue hints at high abundances of the deuterated intermediate nitrogen radicals, ND, NHD, and ND2. So far however, only ND has been detected in the interstellar medium. In this paper, to constrain the formation of ammonia, we aim at determining the NHD/NH2 and ND2/NHD abundance ratios, and compare them with the predictions of both pure gas-phase and grain-surface chemical models. We searched for the fundamental rotational transitions of NHD and ND2 towards the class 0 protostar IRAS16293−2422, towards which NH, NH2 and ND had been previously detected. Both NHD and ND2 are detected in absorption towards the source. The relative abundance ratios NH2:NHD:ND2 are close to 8:4:1. These ratios can be reproduced by our gas-phase chemical model within a factor of 2–3. Statistical ratios as expected from grain-surface chemistry are also consistent with our data. Further investigations of the ortho-to-para ratio in ND2 , both theoretical and observational, could bring new constraints to better understand nitrogen hydride chemistry.

Correlation of The Mechanical Properties of Silicon Oxynitride Films to Processing Parameters, Film Stoichiometry, and Hydride Bond Concentration

A selective range of hydrated silicon oxynitride thin films (SixOyNz:H) have been characterized in terms of their stress, hardness, and modulus in order to mechanically qualify them for use as an encapsulation layer for memory devices (e.g., Flash and EPROM memories). These films are analyzed by RBS and HFS for stoichiometry. The films exhibited stress values between 1.86 x 109 to -3.54 x 109 dyne/cm2 and showed a linear correlation with the hydride ratio (N-H/Si-H). An Ultra Micro-Indentation System (UMIS) measured hardness values between 10.5 GPa to 16.2 GPa while the elastic modulus varied between 119.1 to 141.2 GPa. The monatomic increase of modulus with hardness is attributed to increased amounts of nitrogen and nitrogen hydride bonding in the silicon oxynitride samples.

Wolfram-Carbonylkomplexe mit Stickstoff-Wasserstoff-Liganden [1] / Tungsten Carbonyl Complexes with Nitrogen Hydride Ligands [1]

Synthesis, properties and reactions of [(OC)5W]2N2H2, [(OC)5W]2N2H4, (OC)5WN2H4, (OC)5WNH3, [(OC)4PØ3W]2N2H4, [(OC)4PØ3WN2H4], [(OC)5W-N2H2-W(CO)4PØ3], [(OC)5W-N2H2-W(CO)4P(CH3)3] and [(OC)5WNHCH3NHC6H5] are reported. The hydrazine complexes are synthesized by ligand exchange from the corresponding tetra-hydrofuran complexes. Oxidation by various oxidizing agents yields the diazene complexes, in most cases very low yields. Substitution of CO by phosphanes leads to reduced stability of the compounds. All complexes undergo base catalysed H-D exchange yielding the corresponding ND derivatives; the diazene complexes show a much faster exchange than the corresponding hydrazine and ammonia complexes, which is explained by the higher acidity of the N2H2 protons. The diazene complexes disproportionate under base catalysis to hydrazine and dinitrogen compounds, the latter of which loose the N2 ligand immediately. The diazene ligand of [(OC)5W]2N2H2 cannot be alkylated by reactions with (CH3)2SO4, LiCH3 or CH2N2; instead, LiCH3 as well as CH2N2 cause disproportionation to N2H4 and N2 complexes. UV irradiation of [(OC)5W]2N2H2 in THF leads to substitution of CO by THF. The THF complexes can be converted to the phosphane substituted diazene complexes. The IR, UV-VIS and 1H NMR spectra of the (OC)5W complexes are nearly identical to those of the analogous Cr and Mo compounds. The unsymmetrical phosphane diazene complexes, however, show a quartet of the N2H2 protons in the 1H NMR spectra with coupling constants of 25-26 Hz for the protons on the NN double bond. This value points to a trans configuration of the diazene ligand and its complexes respectively.