VESUVIO: a novel instrument for performing spectroscopic studies in condensed matter with eV neutrons at the ISIS facility

A combined INS and DINS study of proton quantum dynamics of ice and water across the triple point and in the supercritical phase

“…Recent DINS and INS experiments on ice and liquid water have been performed on the VESUVIO spectrometer at the ISIS spallation neutron source (UK) [4] on an attosecond time scale (i.e. 10 À15 s-10 À16 s) -at T = 271 K [10], T = 285 K [14] and T = 673 K [22] and on the time-of-flight neutron Chopper spectrometer SEQUOIA at the Spallation Neutron Source (SNS) -at T = 271 K and T = 285 K [2] -using an incident neutron energy of the chopper of E i = 600 meV, respectively.…”

“…The picture proposed is that this effect arises from a competition between anharmonic quantum fluctuations of intermolecular bond bending and intramolecular covalent bond stretching, where the latter fluctuations tend to strengthen H-bonds whereas the former to weaken H-bonds. Quantum effects, such as those associated with the breaking and distortion of hydrogen bonds are uniquely revealed by using Deep Inelastic Neutron Scattering (DINS), also called Neutron Compton Scattering (NCS) [3][4][5], measuring the proton momentum distributions, n(p), and mean kinetic energy, hE K i. In parallel novel simulation techniques have been also employed to calculate the n(p), using state of the art open path integral simulations [6,7] implemented with first principles molecular dynamics [8] within the Path Integral Car-Parrinello Molecular Dynamics (PICPMD) framework [9].…”

The quantum nature of the OH stretching mode in ice and water probed by neutron scattering experiments

“…Currently, this technique is available a) Electronic mail: roberto.senesi@uniroma2.it only at the VESUVIO beam line operating at the ISIS neutron facility. [13][14][15] Measurements were carried out on ice and liquid water, in stable and metastable phases, in a wide temperature range, 269 K <T < 673 K. Experimental results showed a remarkably diverse behavior of the mean proton kinetic energy E K and of n(p) as a function of T. 4,11,12,[16][17][18] While a quantitative agreement between experiments and theoretical predictions, using independent DINS data analyses, was found for the proton momentum distributions in ice 18 and supercritical water, 19 discrepancies were reported for liquid water at room temperatures and below. Of particular significance is the excess of E K observed across the density maximum at 277 K and across the supercooled phase at 272 K, 16 whose interpretation is still the subject of debate.…”

YAP scintillators for resonant detection of epithermal neutrons at pulsed neutron sources

“…VESUVIO usually operates with the filter difference technique 15 where the detection of the scattered neutrons is performed by 6 Li glass scintillators located in both back-and forward-scattering positions. 14 In the present experiment the instrument was, instead, set up to operate in the resonance detector (RD) configuration. In this case, scattered neutrons were recorded by a suitable detection system consisting of a combination of an analyzer foil and a photon detector.…”