Information content of an INS spectrum

To make the most of the INS technique and to avoid pitfalls some knowledge of the physics of neutron scattering is desirable. The theory of neutron scattering can be presented at various levels of sophistication. In the classic texts [14, 15] the formalism and the accompanying symbolism can look formidable indeed. In this book, while the presentation of the necessary theory is accurate and rigorous, our concern is the information content of the equations rather than their derivation. Our aim is to acquaint the reader with the basic concepts of neutron scattering, to make the connection between theory and experiment and to show how useful information can be extracted from the experimental data. 

The INS technique can be simply summarised. The observed positions of the transitions (the eigenvalues) are a function of the molecule s structure and the intramolecular forces, as in optical spectroscopy, and correspond to the energies lost by the neutron. The strength of the observed transition is a function of the atomic displacement occurring during that vibration (the eigenvector) and the momentum lost by the neutron. The atomic displacements are again determined by the molecule s structure and the intramolecular forces but 

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