The Analysis of Vibrational Spectra: Past, Present and Future.

Vibrational spectroscopy can be said to have started with the seminal work of Coblentz in the 1900s, who recorded the first recognisable infrared spectra. Today, vibrational spectroscopy is ubiquitous and there are many ways to measure a vibrational spectrum. But this is usually only the first step, almost always there is a need to assign the resulting spectra: "what property of the system results in a feature at this energy"? How this question has been answered has changed over the last century, as our understanding of the fundamental physics of matter has evolved. In this Perspective, I will present my view of how the analysis of vibrational spectra has evolved over time. The article is divided into three sections: past, present and future. The "past" section consists of a very brief history of vibrational spectroscopy. The "present" is centered around ab initio studies, particularly with density functional theory (DFT) and I will describe how this has become almost routine. For the "future", I will extrapolate current trends and also speculate as to what might come next.