[en] We have measured the incoherent scattering function of liquid para-hydrogen, pure and mixed with neon, in various thermodynamic conditions, using inelastic neutron scattering. The experiments were carried out on TOSCA-II, a time-of-flight, inverse-geometry, crystal-analyzer spectrometer. After an accurate data reduction, the low-energy parts of neutron spectra recorded in forward scattering have been analyzed in the framework of the Gaussian approximation and fitted through a Levesque-Verlet model for the velocity auto-correlation function. Despite the excellent quality of these fits, the velocity auto-correlation function derived from the forward-scattering data appears totally unable to properly describe the backward-scattering ones. These findings prove a clear breakdown of the Gaussian approximation in these semi-quantum liquids

[en] From the data of a transmission experiment we have extracted the total neutron cross-section of a sample of gaseous hydrogen (T=75.03 K, p=84.8 bar, n=8.42 nm^-3) with a thermodynamic equilibrium ortho-para content (48% ortho, 52% para). The experiment was carried out on the PEARL instrument operating at the ISIS pulsed neutron source. After an accurate data reduction, the neutron spectra have been analyzed in the framework of the Modified Young and Koppel (MYK) theory, which is a successful extension to interacting fluids of the original Young and Koppel model valid for a dilute gas of hydrogen molecules. The total cross-section calculated with MYK theory, whose unique unknown parameter - the mean kinetic energy of the molecular centre of mass - was obtained through an independent path integral Monte Carlo simulation, shows a satisfactory agreement with the experimental results

[en] Following a first demonstration on the potentials of time-of-flight neutron diffraction in the microstructural characterisation of archaeological bronzes, we present here the results of a further systematic study on the topic. The experiments were performed on standardised specimens and original archaeological bronze findings at the powder diffractometer ROTAX. The possibility to achieve various metallographic data concerning alloy composition, homogeneity, dendritic structure, metal and mineral phases, as well as the effects of hardening, annealing, and re-crystallisation processes was successfully demonstrated. Furthermore, we also report a texture analysis on a Roman coin, which provided a clear striking fingerprint thus demonstrating a powerful authentication method

[en] These proceedings represent papers presented at the 13th International Conference on Spectral Line Shapes which was held in Firenze,Italy from June 16-21, 1996. The topics covered a wide range of subjects emphasizing the physical processes associated with the formation of line profiles: high and low density plasma; atoms and molecules in strong laser fields, Dopple-free and ultra-fine spectroscopy; the line shapes generated by the interaction of neutrals, atoms and molecules, where the relavant quantities are single particle properties, and the interaction-induced spectroscopy. There were 131 papers presented at the conference, out of these, 6 have been abstracted for the Energy Science and Technology database

[en] Single-wall carbon nanotube structure has been investigated by neutron diffraction using the SANDALS time of flight diffractometer (at R.A.L.). The Q range of the detector allows for the determination of single the tube diameter, diameter distribution, and mean number of tubes in the bundle. Results are compared to theoretical predictions

[en] The structure factor of deuterium gas has been measured, close to the critical region, by S.N. Ishmahev et al. and by M. Zoppi et al. by means of neutron scattering. The results, qualitatively similar, show discrepancies which are above the estimated experimental accuracies, however. The different scattering angles used in the two experiments (22-135deg for the former and 5-20deg for the latter), and the consequently different inelastic scattering corrections, are probably responsible for the inconsistency. Simple considerations show that using small scattering angles gives a better reliability of the results. (orig.)

No abstract available

[en] The design of a neutron spectrometer for inelastic scattering with inverse geometry configuration is presented. The main new characteristics of the proposed design are the use of a Venetian blind arrangement for the crystal analysers and the insertion of a para-hydrogen filter for the suppression of higher-order reflections. Based on this design, a prototype arm was built and tested at ISIS Spallation Neutron Source (UK). The results of the test measurements, showing the performances of the system, are presented and discussed

[en] The inelastic neutron scattering spectra of LiH and NaH have been measured at low temperature. After an accurate evaluation of multiple scattering and multiphonon contributions, the proton-projected density of phonon states has been extracted for both samples. The NaH spectrum was previously totally unknown, while, as far as LiH is concerned, the present result substantially improves old neutron measurements, showing a better agreement with the existing lattice dynamics calculations. The proton mean kinetic energy in LiH, derived from the density of phonon states, is compared to new deep inelastic neutron scattering results

[en] A quantum model, consisting of a rotating harmonic oscillator, has been developed for the neutron scattering cross section of a homonuclear diatomic molecule. The translationaldynamics of the molecular centers of mass is also accounted for. The model is developed in particular for the case of the integral neutron cross section of the hydrogen isotopes. It is shown that, to the lowest-order approximation, the picture reduces to that of a rigid-rotor model modulated by a Debye-Waller factor. However, the accurate results shows a nonnegligible correction that should be taken into account if a proper analysis of the experimental diffraction data is to be performed. (orig.)