Every element and molecule absorbs or emits light in a unique pattern or spectrum. That makes spectroscopy one of the most widely used and effective methods for studying matter. Raman and IR absorption spectroscopies, for example, are used to identify specific molecules and reveal their structural information. Visible, UV, and fluorescence spectroscopies work similarly and can sometimes even measure single molecules.
NMR spectroscopy measures the absorption of electromagnetic radiation at radio frequencies. It’s increasingly being used in the biological and medical sciences because of its extraordinary ability to determine the structure and behavior of proteins and other exceptionally complex molecules. NMR spectroscopy uses a very different approach that’s based on forming coherences.1 A coherence is a quantum mechanical superposition state that consists simultaneously of two states, just like Erwin Schrödinger’s famous cat. Although it may seem strange, such a situation is possible in quantum mechanics, where things are described...
