Thermal neutron scattering is a space-resolved spectroscopic technique which probes atomic motions at nanometric length scales and on time scales ranging from sub-picoseconds to about 10 nanoseconds. An important application is quasielastic neutron scattering (QENS) from proteins, which can be used to probe the internal stochastic motions in proteins. Since proteins contain a large amount of hydrogen atoms and incoherent scattering by the latter dominates by far all other contributions, QENS probes here essentially self-correlations in the dynamics of the hydrogen atoms. Each (hydrogen) atom in a protein participates in a variety of motions, ranging from fast local bond-vibrations to slow ``breathing motions’’ of the whole protein, which can be detected with flash photolysis and fluorescence techniques on time scales as long as seconds and even hours. As a result, the dynamics probed by QENS is characterized by power-law relaxation processes, leading to self-similarity in time, i.e. to an invariance under a change of the time scale.
G. R. Kneller, Franck-Condon picture of incoherent neutron scattering PNAS USA, 30 August (online) 2018
G. R. Kneller, Asymptotic neutron scattering laws for anomalously diffusing quantum particles J. Chem. Phys. 145(4), 044103–7, 2016 (Editor’s choice 2016)