Vibrational spectroscopy with neutrons

Mitchell, P.C.H., Parker, S.F., Ramirez-Cuesta, A.I., and Tomkinson, I., Vibrational Spectroscopy with Neutrons with Applications in Chemistry, Biology, Materials Science and Catalysis. World Scientific, Singapore, 2004. 

P. Mitchell, S. Parker, A. Ramirez-Cuesta and J. Tomkinson, Vibrational Spectroscopy With Neutrons With Applications in Chemistry, Biology, Materials Science and Catalysis , World Scientific Publishing, June 2005, Vol. 3. 

Vibrational dynamics are dominantly represented with normal modes that are coherent harmonic oscillations of all degrees of freedom at the same frequency [Wilson 1964 Califano 1981 Long 2002 Ferraro 2003], In the classical regime, normal coordinates - the eigenvectors of the dynamical matrix -are determined only to an arbitrary proportionality factor. In other words, the effective mass associated to a normal mode is arbitrary. This is of no consequence for optical spectroscopy techniques (infrared and Raman) that cannot probe masses, because of tiny momentum transfer values. Only recently, effective masses have been determined thanks to vibrational spectroscopy with neutrons [Ikeda 2002], The existence of well-defined (of course) effective masses should be included in further theoretical developments. 

An overview of basic physics necessary to understand neutron scattering experiments is presented below. This section is a brief introduction to vibrational spectroscopy with neutrons. More details can be found in Ref. [Lovesey 1984], Experienced readers should ignore this rather superficial introduction. 

Vibrational spectroscopy with neutrons is a spectroscopic technique in which the neutron is used to probe the dynamics of atoms and molecules in solids. In this introductory chapter we provide a descriptive account of the discovery and properties of the neutron, the development of neutron scattering, how inelastic neutron scattering spectroscopy compares with infrared and Raman spectroscopy and the benefits of using the neutron as a spectroscopic probe. 

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