Analytical Theory

Continuing the theory and practice themes from previous columns, the theory portion of this column will be a discussion of the proper way of handling the infrared spectral interpretation of mixtures. In my opinion, mixtures are the biggest obstacle to interpreting infrared spectra, and I will share with readers five tried-and-true techniques for dealing with them. The practice portion of the column will give the answer to the last installment’s problem, and complete the spectral analysis of straight chain alkanes.

Polarized Raman spectra are presented along with a discussion of the association of the symmetry species of the normal vibrational mode and the depolarization ratio of Raman scattering.

Mid-infrared quantum cascade lasers, recently developed and commercialized, have unique properties that advance the analytical capabilities of IR spectroscopy in many ways. Bernhard Lendl of Vienna University of Technology in Austria explains these developments.

An interview with Rohit Bhargava, the winner of the 2012 FACSS/SciX Innovation Award.

The field of mid-infrared (mid-IR) imaging has made significant developments in recent years, but the theory has not kept pace. Rohit Bhargava, an associate professor of engineering at the University of Illinois at Urbana-Champaign and the associate director of the University of Illinois Cancer Center, recently undertook studies to address that gap. Spectroscopy spoke to him recently about that work.

The connection between the mathematics of classical least squares and the graphical displays used to present it is examined in further detail.

The authors continue their ongoing discussion of classical least squares with a look at spectroscopic theory.

Here, we continue our treatment of symmetry and group theory by introducing a very useful mathematical tool in group theory. It has two names in common use, but thankfully they both have the same acronym: GOT.

The authors continue their discussion of the classical least squares approach to calibration.

In this month's installment of "Chemometrics in Spectroscopy," the authors begin a new subseries with the goal of explaining the classical least squares algorithm.

In the third part of this series, David Ball starts getting into the mathematical aspects of group theory, aspects that ultimately become useful in spectroscopy.

In the previous installment of this column, David Ball introduced the five types of symmetry elements that are important in physical science. Here, he discuss why it’s called "group" theory in the first place.

Group theory is the field of mathematics that includes, among other things, the treatment of symmetry. Well, it turns out that molecules have symmetry, so group theoretical principles can be applied to molecules. Because spectroscopy uses light to probe the properties of molecules, it might not be surprising that group theory has some application to spectroscopy. Here, we start a multipart discussion of symmetry and group theory.

In this tutorial, the authors explain how naturally occurring stable isotopes contribute to experimentally determined mass spectra and how this information can be exploited in quantitative experiments, structural elucidation studies, and tracer methodologies. The first installment of this series focuses on the theoretical aspects of stable isotopes and the calculation of their distribution patterns.

Theory of Raman Spectroscopy