No abstract

The infrared spectra of solid and matrix-isolated methylamine, methylamine-d2, methyl-d3-amine, and methyl-d3-amine-d2 have been recorded from 4000 to 250 cm−1. The Raman spectra of the four isotopic species have also been recorded and depolarization values measured. The elusive NH2 twisting vibration has been located in the solid-phase infrared spectra of CH3NH2 and CD3NH2, and the assignment is in agreement with both the product rule and earlier assignments for this normal mode in hydrazine. A temperature-dependent hydrogen-bonding study has been carried out and ΔH° for H-bond formation in methylamine-d2 was found to be −660 cal/mole.

The infrared spectra of crystalline hydrazine and hydrazine-d4 have been recorded from 33 to 400 cm−1. All spectral bands have been assigned to lattice vibrations according to whether they arose primarily from a translational motion or a librational mode. However, there is strong evidence that these two motions are coupled and thus may not be described accurately as one motion or the other. An attempt is made at correlation between the observed and calculated shifts upon deuteration and some simple force constant calculations have been made. Finally, the far-infrared spectrum distinguishes between the two proposed crystal structures (C2h2 and C22) and the results are consistent only with the C22 structure.

Pure methane and 10 mol % methane in Ar have been studied in the region of methane’s ν1 totally symmetric stretching mode near 2910 cm−1 (ω0, the signal maximum or zeroth spectral moment frequency). Densities from 0.0795 (3 bar) to 15.0 (2100 bar)×1021 mol/c.c. were examined using Ar+ laser illumination at 514.5 nm. Frequency shifts of ν1’s ω0, and the zeroth moment depolarization ratio, ρD, values as a function of pressure were recorded. Previous ω0 shifts vs density were generally confirmed and were extended to higher densities. This allowed a shallow minimum to be observed in this data. It was correlated with the ρD values. These latter values were examined to see whether or not they were as sensitive as the frequency shift results were to the local reorientational friction coefficient tensor fr (potential-energy interactions) in methane and the Ar/CH4 solutions. The initial (3.5–1000 bar data) depolarization results were interpreted with two models of methane in mind. The first, a conventional view that is based upon the concept that higher densities cause distortions in the molecular shape (lower symmetry), and the second, which makes use of the known fact that the symmetry of methane at low pressures is less than Td. Therefore, as the density and fr increase quantum rotation slows and the rotation-vibration interaction effectively ceases and causes the molecules to pack tightly and the well-known Td symmetry is achieved.

Low-grade carbonaceous gold ore (0.01 to 1.8 oz/ton of gold) from the Carlin mine in Elko county, Nevada, has been characterized by a variety of analytical and spectroscopic techniques with emphasis on vibrational spectroscopy. A particular concern was determining the nature of the carbon-containing material in the ore. It was found that in addition to the anticipated carbonate, finely disseminated elemental carbon is present in amounts ranging from 0.062 to 0.43 wt. %. Contrary to previous reports, no detectable amounts of humic acid materials or organic hydrocarbons are present in any of the samples investigated.