The vibrational spectrum and lattice dynamics of polycrystalline ammonium hydrosulfide

Abstract

The infrared spectra of NH4HS and ND4DS have been recorded from 200 to 4000 cm−1 at liquid nitrogen temperatures, and the Raman spectra of these substances have been recorded from 0 to 4000 cm−1 over the temperature range 83–390°K. No evidence of a second solid phase was obtained. Internal and external fundamentals were assigned, in detail, based on selection rules, isotopic frequency shifts, and analogy with other structurally similar salts. Barriers to anion and cation reorientation of 3.8 and 1.9 kcal/mole, respectively, have been calculated from librational assignments. The implications of the infrared spectrum of NH4HS for the possible spectroscopic detection of this substance in the atmosphere of the planet Jupiter are discussed.

Giant-planet chemistry: Ammonium hydrosulfide (NH4SH), its IR spectra and thermal and radiolytic stabilities

“…See Fig. 1 of Bragin et al (1977) for an illustration of the unit cell of crystalline NH 4 SH based on the work of West (1934). Several observations argue for a high purity of our NH 4 SH ices.…”

“…The earliest IR work appears to be that of Bragin et al (1977) who showed a single spectrum at 98 K of the crystalline solid. Aside from it having a few small extra absorptions at 1750-1500 cm À1 , and showing traces of trapped NH 3 , that spectrum agrees with our Fig.…”

“…1) are in qualitative agreement with the three published spectra, one for the amorphous solid and two for the crystalline, but a more quantitative comparison is desirable. Unfortunately, the IR spectrum of Bragin et al (1977) has a vertical axis with a numerical scale, but no ice thicknesses were provided, while the spectra of Ferraro et al (1980) are accompanied with ice thicknesses, but no vertical scales with numbers. Therefore, quantitative comparisons of our NH 4 SH spectra with these earlier ones are impossible.…”

“…Vapor pressure measurements of NH 4 SH were first reported by Isambert (1881), a melting point was published by Briner (1906), and crystallographic studies were done by West (1934). The first published infrared (IR) spectra of solid NH 4 SH were from Bragin et al (1977), who identified the strongest mid-IR absorptions as being near 3000, 1830, 1400, and 470 cm À1 ($ 3.3, 5.5, 7.1, and 21 lm) for the crystalline solid near 100 K. A different NH 4 SH ice was reported to have broad IR absorptions, and subsequent work by Ferraro et al (1980) identified this solid as amorphous NH 4 SH, with the amorphous-to-crystalline phase change being near 160 K. Nearly 30 years later the IR optical constants of NH 4 SH were published by Howett et al (2007). Work in other spectral regions is limited to the electronic spectra of Lebofsky and Fegley (1976), who reported that the ultraviolet-visible reflectance spectrum of NH 4 SH is relatively featureless and flat, albeit with a slight rise from 300 to 1000 nm (slight red slope).…”

Uranus deep atmosphere revealed

“…But as noted above most of the uncertainty in the measurements is in AS for the reaction. The other possible source of error in extrapolation would be a phase change in NH4SH, but Bragin et al (1977) did not see evidence for one down to 83 K. In view of all of the above, we favor our calculations with the strongly enriched mixing ratios, reserving our doubts about Kp until improved laboratory data become available.…”