Raman Addition Spectroscopy with a Rotating Cell

Abstract

A new technique is described for obtaining quantitative relative intensity measurements, in the study of solution equilibria by laser-Raman spectroscopy, without the necessity for adding an internal standard to the sample. A rotating cylindrical double cell with separate compartments for sample and reference is used to superimpose the Raman spectra of sample and reference and hence avoid any uncertainties arising from the displacement of the equilibrium by reference substance addition.

Device for Raman Difference Spectroscopy

“…The detection of the Raman signals of the samples in the two compartments of the cell was triggered by the rotation frequency of the cell (>1000 rpm) and readout with a PM. This very useful setup was later slightly modified (e.g., by use a four-compartment cell) and successfully applied to study, e.g., small wavenumber shifts in binary mixtures. ,− Because a PM can be read out very quickly (>1000 rpm), the time elapsing between the detection of the two Raman signals of the two rotating cell compartments is short enough to rule out environmental perturbations (thermal drifts of the apparatus, laser fluctuations, etc.) of one of the Raman signals compared to the other.…”

Thermodynamics of Preferential Solvation of Electrolytes in Binary Solvent Mixtures

“…Therefore, comparing Equations 31 and 30, AG,-0 = AGps 0 /n -RT ln [(n + 1 -i)/i] (32) or in the form of equilibrium constants (33) be formulated as the weighted average of the chemical shifts arising from all possible arrangements of solvent around the ion (13). Hence, if the ith species has an intrinsic shift of 6t, the observed shift 6 is given by…”

Raman spectroscopy

“…The rotating cell developed by Kiefer and Bernstein for preventing the destruction of absorbing species (1) has generated several useful possibilities. A variation has been designed to obtain gas phase spectra at high temperatures (50), and several workers have used split rotating cells for measurements of small frequency shifts and/or difference spectra (51, 52), or for the superimposition of external standard spectra (53). A second approach to obtaining difference spectra, using two cells, has also been described (54), as has a universal mount for a rotating cell for liquids and solids.…”