Frank G. Baglin

Vibrational analysis of the infrared and Raman spectra of oxalyl bromide in the crystalline and fluid states

The vibrational spectrum of oxalyl bromide [COBr]2, has been recorded between 4000 and 33 cm−1. The infrared spectra of oxalyl bromide have been examined in the solid, liquid, and gaseous states, and the Raman spectra of the solid and liquid have been observed and qualitative depolarization ratios have been measured. The vibrational spectrum of the crystalline material has been interpreted on the basis of C2h molecular symmetry and C2h5 space group symmetry. Two of the three external lattice modes have been observed in the far‐infrared spectrum, and at least four of the six Raman active external lattice modes have also been observed. Six bands appear in the infrared and Raman spectra of the liquid/gaseous states which do not appear in the spectra of the solid. Thus, in the fluid states, molecules with both C2h and C2υ molecular symmetries appear to be present. The enthalpy difference between the two isomers was determined by a variable temperature study to be 2.9 ± 0.1 kcal/mol with the trans isomer being...

Characterization of Carlin-Type Gold Ore by Photoacoustic, Raman, and EPR Spectroscopy

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.

Interaction induced Raman spectroscopy of the dipole forbidden πu mode in neat CO2 and solutions with N2 as supercritical fluids

The interaction induced Raman spectra (IIRS) of 1:0, 1:1, and 1:3 CO2 :N2 solutions have been studied at 50 °C and 75 °C at densities up to 2.5 times the triple point density (90–3010 bars). M0, M2 , and M4 evaluations have been made upon the πu ν2 Raman dipole forbidden signal. In addition, the absolute Raman scattering cross sections have been evaluated for the 1:0 and 1:1 solutions. A broad low intensity high frequency shoulder was seen in the 1:0 data of ν2 and is identified with a CO2 oscillating on a large cluster of CO2 ; this perturbs the isolated ν2 frequency; the shoulder is not found in the 1:1 or 1:3 solutions. Significant many body cancellation has been observed in the 1:0 data at 50 and 75 °C at near solid densities of the fluid. The nature of the ν2 signal shows that there is a significant difference between the neat and N2 –CO2 solutions. In particular, depolarization measurements upon ν2 in the 1:0 and 1:3 solutions at 50 °C and 1255 bars of pressure showed very different behavior. This w...

Amino-Imino Interconversion in Crystalline 5-Aminotetrazole-Monohydrate

Abstract Laser Raman evidence is presented to support the existence of reversible interconversion of 5-aminotetrazole-H2O and 5-iminotetrazole·H2O in the solid state.

Isothermal density tuning of the depolarization ratios from the ν1 mode of methane

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 th...

High pressure Raman studies of molecular reorientation in supercritical ethane

Anisotropic Raman scattering from the symmetric C-C stretch vibration (υ3) of the ethane molecule is used to study the reorientational dynamics of supercritical fluid ethane. Experiments at constant temperatures, 50°C and 75°C, with densities ranging from 0·48 ρc to 2·8 ρc (ρc = critical density) as well as experiments at constant density, 2·0 ρc, in the temperature range from 50°C to 125°C were carried out. From the spectra, orientational correlation functions were calculated and compared with corresponding correlation functions of the J-diffusion model. The density dependence of the collision parameter β* (at constant temperature) as well as the temperature dependence of β* (at constant density) are given. Although the correlation functions derived from the J-diffusion model show systematic deviations from the experimental ones at high density, the experimental correlation times τθ correlate reasonably with the J-diffusion model. Comparison of the collision frequencies β* of ethane with results obtained...

A theoretical intensity study of the interaction induced Raman spectra of the ν2(πu) mode of CO2 between 100 and 3000 bars of pressure

The density dependent integrated intensities of the interaction induced (ii) dipole forbidden Raman spectra of the CO2 ν2(πu) mode have been calculated by the use of statistical mechanics based on the quadrupole–induced‐dipole (QID) mechanism. The calculated intensities were compared with experimentally determined intensities. The intensities examined were between 5.03 to 17.00×1021 molecules/cm3 and the temperatures examined were 50 and 75 °C. The results indicated that at densities up to approximately 2.5× the triple point density, the integrated intensities can be expressed as a function of the density squared. This density square dependence of the integrated intensity may be due to almost perfect cancellation between constructive intensity originated from (CO2)2 dimers and the destructive intensity of classical three body interactions which have also been calculated. In any case, extra intensity was present as a high frequency shoulder at all densities except the lowest and highest values and was not ...

Raman spectroscopic study of vibrational lifetimes of a tricyclic hydrocarbon system in the liquid state

The Fourier transformed spectra of a totally symmetric A1 vibration in a large organic molecule, C8H12, is reported and interpreted. Equivalence of the widely used Rakov‐Sykora deconvolution procedure to a purely experimental technique offered recently by Griffiths is discussed. Using Raman spectroscopy at various temperatures, a comparison of the intrinsic vibrational lifetimes and the reorientational relaxation times is effected that allows us to propose a mechanism for intramolecular energy transfer for this A1 normal coordinate of C8H12 in the liquid state.

Depolarization-density tuning in supracritical solutions of methane-carbon dioxide

The Raman depolarization ratios (RDRs) for a 10mol% solution of methane in carbon dioxide and the v 1 frequency shifts are reported under supracritical conditions. A striking difference was found between the earlier pure methane results and those reported here. The time correlation functions are interpreted to yield a picture of the methane interacting with the carbon dioxide even at lower densities. The mixture results are also discussed in terms of a theoretical RDR calculations and experiments on carbon tetrachloride. It is believed that the RDR against density (pressure) data reflect the interbody potential function and torques; the quantification has to date, not been achieved.

External Optic Phonons in Tetrazole

The laser Raman spectrum of polycrystalline tetrazole has been recorded at 300°K and at 95°K. The external optic phonon spectrum of tetrazole is shown to be consistent only with the P1 space group. High frequency shoulders have been observed on the three librational 0→1 transitions and have been assigned as quasi LO phonons. Relative infrared band intensity ratios have been calculated from these shoulders and are in agreement with experimental results. The N··· N distance has been calculated as 2.85 ± 0.02 A. The mean librational (torsional) displacements, harmonic force constants, and dipole derivatives have also been calculated. The three 0→1 phonons have been assigned by means of a linear lattice model.