ELSEVIER Physica B 203 (1994) 116 128 Multiple scattering and inelasticity corrections in thermal neutron scattering experiments on molecular systems t j. Dawidowski a, t, J.R. G r a n a d a a'*' x, R.E. Mayer a, G.J. Cuello"' 2, V.H. Gillette a, M.-C. Bellissent-Funel b aComisibn Nacional de Energia Atbmica, Centro Atbmico Bariloche and Instituto Balseiro, 8400 Bariloche, Argentina b Laboratoire Lbon Brillouin (CEA-CNRS), CE-Saclay, 91191 Gi[2sur-Yvette cedex, France Received 26 October 1993; revised 24 April 1994 Abstract In this work we address the problem of multiple scattering and inelasticity corrections in neutrondiffraction measurements for structural studies of molecular systems. A variety of pulsed neutron and reactor experiments was performed on hydrogenous samples under different experimental conditions. Monte Carlo simulations were carried out on the basis of a Synthetic Model to describe the neutron-molecule interaction, and they allowed a simultaneou evaluation of multiple, inelastic and beam attenuation processes into the samples. A very good agreement between measurements and simulations was obtained in all cases, for our demanding choice of samples and experimental conditions. 1. Introduction Neutron scattering techniques are well estab- lished as a powerful tool for the investigation of condensed matter, providing in many cases unique information about its structural and dynamical properties. In particular, a great deal of experi- mental work, using those methods, has been done in recent years to elucidate some fundamental ques- tions about the structure of molecular liquids and amorphous systems. * Corresponding author. Also at Consejo Nacional de lnvestigaciones Cientificas y T~c- nicas (CONICET), Argentina. 2 Also at CRUB, Universidad Nacional del Comahue. *The material contained in this paper is part ofJ. Dawidowski's PhD thesis (Instituto Balseiro, May 1993). The high statistical accuracy achievable today in neutron scattering measurements performed with the use of powerful sources and sophisticated in- struments, does not guarantee by itself the attain- ment of reliable information about the system under study, if we consider that some unavoidable corrections must be applied to the observed spectra. However, the development of adequate procedures to treat them has not paralleled the evolution of source intensity and instrumental quality. In neutron scattering experiments where we seek structural parameters of molecular systems, the in- elastic contribution to the observed spectra con- forms to a pedestal over which the characteristic oscillations of the coherent component are super- imposed, and that pedestal will be, in general, quite 0921-4526/94/$07.00 © 1994 Elsevier Science B.V. All rights reserved SSDI O 9 2 1 - 4 5 2 6 ( 9 4 ) 0 0 1 7 1 - Q