	In the “Molecular Spectroscopy Workshop” column, we have been trying to provide hands-on advice and easy-to-implement tips for analysts who have the responsibility to use spectra to derive answers to questions as quickly as possible. Very often the identity of an unknown is of ultimate importance, and very few analytical chemists coming out of graduate programs have been taught to systematically analyze spectra in order to infer the identity of the source. In addition, it is rare that an industrial environment will provide resources for analysts to be educated in this field. Thus, the availability of any means to provide spectral identification will make the difference between success and failure-acquiring a spectrum is useless if one cannot identify it. In this column, I discuss some of the fundamentals of spectral interpretation, illustrate the use of searching software, including mixture analysis, and show how sometimes the software can provide spectral interpretation.

Articles

Articles in this Issue

Introduction to Interpretation of Raman Spectra Using Database Searching and Functional Group Detection and Identification

	The use of Raman spectroscopy to produce material images whose contrast is derived from chemical or crystallographic species has been quite useful since the introduction of the Raman microscope in 1976, but particularly with the more recent development of more-sensitive and easier-to-use instruments.	 	Read more 

Raman Mapping of Spectrally Non-Well-Behaved Species

	Photoluminescence can provide information about the composition and solid-state structure of a material. The high spectral resolution of a Raman spectrometer can be useful in performing photoluminescence spectroscopy of solid-state materials, particularly when the emission spectra consist of narrow bands or even lines. Having the capability to perform photoluminescence and Raman spectroscopies simultaneously with the same instrument is advantageous, especially when studying two-dimensional (2D) crystals. When used to perform photoluminescence spectroscopy, the Raman spectrometer becomes two instruments in one.

Photoluminescence Spectroscopy Using a Raman Spectrometer

	Raman spectroscopy can be used to determine the temperature of a material when other more direct means are either impractical or not possible. The material’s temperature can affect the peak position of Raman bands. When a Raman band shifts significantly with temperature, the monitoring of the peak position can be the most straightforward manner of determining temperature provided the Raman spectrometer has sufficient spectral resolution. Another method is to determine the temperature from the ratio of the Stokes and anti-Stokes signal strengths of a given Raman band. The latter method requires the ability to detect light at wavelengths longer and shorter than that of the laser and an accurate measurement of the wavelength-dependent instrument response function.

Raman Thermometry

	Here, we examine the problem of photoluminescence from the material being analyzed and the substrate on which it is supported. We describe how to select an excitation wavelength that does not generate photoluminescence, reduces the noise level, and yields a Raman spectrum with a superior signal-to-noise ratio. Furthermore, we discuss the phenomenon of resonance Raman spectroscopy and the effect that laser excitation wavelength has on the Raman spectrum.

Selecting an Excitation Wavelength for Raman Spectroscopy

	Raman spectra of celluloses modified for use in the pharmaceutical, food, and materials industries are compared and analyzed, with the goal of determining spectroscopic features that can be of use in aiding in the determination of physical and chemical properties.
	 

Spectroscopy E-Books-12-01-2016

Introduction to Interpretation of Raman Spectra Using Database Searching and Functional Group Detection and Identification

Raman Mapping of Spectrally Non-Well-Behaved Species

Photoluminescence Spectroscopy Using a Raman Spectrometer

Raman Thermometry

Selecting an Excitation Wavelength for Raman Spectroscopy

Characterizing Modified Celluloses Using Raman Spectroscopy