* Corresponding author. Fax: #54-2944-445299. E-mail address: javier@cab.cnea.gov.ar (J. Dawidowski) Physica B 271 (1999) 212}222 Exploration of the dynamics of condensed matter through neutron total cross-section measurements J. Dawidowski*, J.R. Santisteban, J.R. Granada Comisio & n Nacional de Energn % a Ato & mica and CONICET, Centro Ato & mico Bariloche and Instituto Balseiro, 8400 S.C. de Bariloche (RN), Argentina Received 3 May 1999; accepted 28 June 1999 Abstract We present a novel procedure to extract dynamical information from the inelastic incoherent part of the experimental neutron total cross section. The coherent elastic and inelastic components must be subtracted in order to isolate the incoherent inelastic part. We show how to obtain the one-phonon downscattering component from it, and use this result to evaluate its derivative with respect to the incident neutron wave vector. This provides a function, which serves as an input for the algorithm to extract the density of the states that is presented in this paper. We have applied this method in the case of three metal hydrides: zircaloy, magnesium and niobium, whose total cross sections were measured at a low-#ux neutron source. Those results are in agreement with the inelastic scattering experiments performed at high-#ux sources over the range from 40 to 250 meV.  1999 Elsevier Science B.V. All rights reserved. PACS: 78.70.N; 63.50; 28.20.Cz Keywords: Total neutron cross section; Metal hydrides; Phonon spectra; Optical modes; Debye}Waller factor 1. Introduction Neutron scattering techniques devised to explore the dynamics of condensed matter have attained a high degree of development, and nowadays large facilities with a great variety of spectrometers are available, where the high neutron #uxes allow to obtain good statistics in relatively short times. However, there are situations in which there is still some degree of di$culty in obtaining the informa- tion from such experiments, notably, the non-trivial corrections that have to be performed such as those due to the multiple-scattering and multiphonon e!ects, on which much e!ort was devoted and con- siderable progress has been attained recently [1], or the di$culties that arise when an absolute scale is required for the results [2]. Furthermore, when densities of vibrational states must be extracted from the experimental data, serious di$culties arise if an absolute normalization is required, due to the limited dynamic range in which the experiment is performed. In all those cases an unavoidable amount of corrections have to be performed on the experimental data, and therefore additional experi- mental information to check up the results will always be desirable. 0921-4526/99/$ - see front matter  1999 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 9 9 ) 0 0 2 1 6 - 1