Column: Molecular Spectroscopy Workbench

David Tuschel is a Raman applications manager at Horiba Scientific in Edison, New Jersey, where he works with Fran Adar. David is sharing authorship of the "Molecular Spectroscopy Workbench" column with Fran.

Articles

Raman spectroscopy is extremely useful for characterizing crystalline materials.

Raman Crystallography and the Effect of Raman Polarizability Tensor Element Values

Fran Adar is the Worldwide Raman Applications manager for Horiba Jobin Yvon.

Low frequency Raman scattering measurements can be used to predict
physical properties of polymers and the crystalline polymorphic form of
active pharmaceutical ingredients (APIs). These measurements are made by recording the Stokes and anti-Stokes side of the laser line with the laser centered on the detector. Spectra of polyethylene and linear alkanes were recorded down to 4 cm-1.

Very Low Frequency Measurements of Linear Alkanes

Raman imaging provides detailed crystal orientation information for two-dimensional MoS2 prepared by chemical vapor deposition on silicon substrates. These two-dimensional crystals consist of individual atomic layers of sulfur, molybdenum, and sulfur atoms.

Effect of Layer Number and Crystal Stacking Orientation on the Raman Spectra of Two-Dimensional MoS2

Raman microscopy, combined with X-ray fluorescence, can provide detailed information about extractables and leachables from medically implantable devices.

Use of Raman Microscopy to Characterize Extractables and Leachables

Raman measurements can be used to infer the temperature of a material based on the Stokes and anti-Stokes band signal strengths, and by applying a predefined mathematical relationship. In reality, the temperature, Raman shift, and laser excitation wavelength all interact, and should be considered to better understand these measurements.

Raman Thermometry: Understanding the Mathematics to Better Design Raman Measurements

Raman 2D-COS spectral data provide information on conformational changes of polymers. Here, Raman spectra of ethylene vinyl acetate and vinyl acetate copolymer are measured and interpreted, enabling a description of morphological changes related to the vinyl acetate group.

Raman Analysis of Ethylene Vinyl Acetate Copolymers–Using 2D-COS for Identifying Structural Changes

When stress is applied to an object, it can produce strain. Strain can be detected through changes in peak position and bandwidth in Raman spectra. Here, we show examples of how strain in technologically impor tant materials appears in
the Raman spectra.

Stress, Strain, and Raman Spectroscopy

The spectral behavior of water is studied using Raman with an NIR spectrograph and dual wavelength lasers for measurements of both the fingerprint and the OH stretching regions. Raman spectra are recorded between 5 ⁰C and 80 ⁰C, and treated with both band-fitting and the 2D-COS algorithm revealing improved insights into the spectral behavior of water.

Measurement of the Temperature Dependence of Water Using a Near-Infrared Raman Spectrograph

The differentiation of polymorphs is important, particularly in the pharmaceutical industry. We demonstrate the practicality of using Raman spectroscopy to differentiate crystal forms for polymorph characterization and screening, and explain aspects of chemical bonding and solid state structure that affect the Raman spectra of crystal lattice vibrational modes.

Raman Spectroscopy and Polymorphism

Two-dimensional correlation spectroscopy (2D-COS) can reveal subtle chemical interactions that are difficult to discern when analyzing individual spectra. A demonstration
of the subtleties of this technique can be seen in the analysis of ethanol–water and ethanol–methanol mixtures.