The use of direct geometry spectrometers in molecular spectroscopy

The advantages and disadvantages of the use of direct geometry spectrometers for molecular spectroscopy and catalysis studies are described. We show that both direct and indirect geometry INS spectrometers are important tools for the study of industrially relevant areas such as catalysis, proton conductors and gas separation. We propose a novel hybrid instrument, Cerberus, that would offer high sensitivity and high-to-reasonable resolution across the entire ‘mid-infrared’ spectral range that would effectively advance research in these areas. 1. Inelastic neutron scattering spectroscopy Inelastic neutron scattering (INS) spectroscopy [1] is a form of vibrational spectroscopy that is complementary to the conventional methods of infrared and Raman spectroscopies. Its usefulness derives from the properties of the neutron, which is a neutral particle of mass 1.00866 amu, almost identical to that of the hydrogen atom, 1.00794. The neutron has a magnetic moment, which has resulted in it becoming an essential tool for fundamental studies of magnetism [2]. Neutrons are scattered by atomic nuclei via the strong force and since the nucleus is only ~0.1% of the diameter of the atom, neutrons are highly penetrating. The nuclear scattering also means that there are no symmetry-based selection rules, so in principle all modes are allowed in INS spectroscopy. The intensity, S, of an INS transition is given by [1]: