Thermal and Electron-Induced Reactions of Hydrazoic Acid (HN₃) Adsorbed on Gold and Ice

Abstract

The chemistry of hydrazoic acid (HN 3 ) on polycrystalline gold and amorphous ice was studied as a function of HN 3 exposure, temperature, and X-ray irradiation using reflection absorption infrared spectroscopy (RAIRS) and X-ray photoelectron spectroscopy (XPS). On Au, HN 3 was found to adsorb molecularly at 100 K. In contrast, at 100 K the reaction of HN 3 with ice was dominated initially by deprotonation and the formation of azide ions (N 3 -). At higher HN 3 exposures on ice, RAIRS data was consistent with molecular adsorption, although a distinct, more strongly bound molecular state was also observed that is attributed to hydrogen bonding between H 2 O and HN 3 . Annealing HN 3 adsorbed on Au resulted in predominantly molecular HN 3 desorption while in the HN 3 /ice system molecular desorption was accompanied by the production of ammonium azide (NH 4 + N 3 -). In contrast, NH 4 + N 3was not observed on the Au surface during annealing experiments. The formation of NH 4 + N 3is postulated to derive from the reactions of NH radicals, formed as a result of NN-NH bond cleavage, within the adsorbate layer. In both the HN 3 /ice and HN 3 /Au systems, secondary electrons generated by X-ray irradiation induced NH 4 + N 3formation and nitrogen desorption, which are consistent with the following net reaction: 4HN 3(a) f NH 4 + N 3(a)-+ 4N 2(g) v

Formation of Nitrogen and Hydrogen‐bearing Molecules in Solid Ammonia and Implications for Solar System and Interstellar Ices

“…Aside from the absorption features of hydrazine, we also observed a peak at 2023 cm À1 . That peak is most likely due to the formation of AgN 3 on the silver substrate, similar to that observed on the gold surface (Carlo et al 2001). At 190 K, all reactants and products sublimed or decomposed.…”

“…The new feature at 1514 cm À1 can be assigned to the 2 bending of the amino radical ( NH 2 ), that at 2088 cm À1 to hydrogen azide (N=N=NH; Shimanouchi1977). It should be mentioned that the latter absorption could also originate from ammonium azide (NH 4 N 3 ; Carlo et al 2001). Note that Gerakines et al (1996) observed a similar peak at 2115 cm À1 .…”

Reactions of Hydrazoic Acid and Trimethylindium on TiO2 Rutile (110) Surface: A Computational Study on the Formation of the First Monolayer InN

“…In the HN 3 /TiO 2 system, both the molecular (HN 3 (a)) and dissociated adspecies, N 3 (a) and H(a), with different adsorption structures, such as end-on and side-on configurations, were observed by FTIR spectroscopy under the conditions of high HN 3 dosage at room temperature and have been confirmed by the optimized structures computationally. Similar results have been reported in some other systems involving HN 3 (a) on polycrystalline gold, amorphous ice 13 and C(100) surfaces with similar experimental conditions. Upon UV irradiation or at higher surface temperatures, only the atomic N-adsorbates can ultimately survive on the TiO 2 surface; this is also similar to the behavior of HN 3 on GaAs, Si(100)-2 × 1, , Si(111)-7 × 7 and Al(111) surfaces.…”

Low-Temperature Oxidation of Nitrided Iron Surfaces

“…Substrates were mounted on dedicated UHV manipulators (McAllister Technical Services) with capabilities for precision xyz translation, rotation, and sample cooling as well as direct sample heating. In chamber-1, polycrystalline iron samples were mounted onto a tantalum foil that was spot-welded via copper rods to a ceramic feed-through coupled to a UHV manipulator, as previously described . In chamber-2, an iron mirror (1 cm diameter) was spot welded via Ta strips onto the copper rods.…”