Molecular inelastic neutron scattering

B.S. Hudson, A. Warshel R.G. Gordon (1974). J. Chem. Phys., 61, 2929-2939. Molecular inelastic neutron scattering computational methods using consistent force fields. 

Vibrational spectroscopy provides detailed infonnation on both structure and dynamics of molecular species. Infrared (IR) and Raman spectroscopy are the most connnonly used methods, and will be covered in detail in this chapter. There exist other methods to obtain vibrational spectra, but those are somewhat more specialized and used less often. They are discussed in other chapters, and include inelastic neutron scattering (INS), helium atom scattering, electron energy loss spectroscopy (EELS), photoelectron spectroscopy, among others. 

Highly energetic compounds with potential use in explosive devices must be characterized completely and safely, particularly as the explosive character may be linked directly to vibrational modes in the molecular structure, hence the application of computational methods to complement experimental observations. ANTA 5 has been the subject of various studies and, as an adjunct to one of these and to confirm the results of an inelastic neutron scattering experiment, an isolated molecule calculation was carried out using the 6-311G basis set <2005CPL(403)329>. 

Supplementary to other vibrational spectroscopies, inelastic neutron scattering (INS) spectroscopy is a very useful technique for studying organic molecules as it is extremely sensitive to the vibrations of hydrogen atoms. INS spectroscopy has been used to analyze the molecular dynamics of the energetic compound ANTA 5 <2005CPL(403)329>. 

The above molecular dynamics results have been confirmed by incoherent inelastic neutron scattering (IINS) measurements on xenon hydrate (Tse et al., 2001 Gutt et al., 2002). In earlier measurements on methane hydrate, the dominant... 

Other materials which have been characterized by inelastic neutron scattering include silver A and 13X zeolites. Measurements of the scattering from ethylene-H4 and its partially deuteriated derivatives adsorbed by silver 13X zeolite have revealed all the three molecular librations. These were assigned to their respective axes from the deuteriation shifts.87... 

Inelastic neutron scattering (INS) measurements have been successfully used to study dynamical phenomena such as molecular or lattice vibrations in pristine C60 [43] and a variety of fullerides [44-48]. When INS spectra are collected on instruments with a large energy window, it is possible to observe all phonon modes including the molecular vibrations and the generalised phonon density-of-states (GDOS) can be directly calculated. 

Figure 4.2. Temperature dependence of the rate constant of electron transfer (Icet) in myoglobin modified covalently by donor-acceptor groups (a) and the deviation of various dynamic quantities from normal harmonic behaviour obtained by molecular dynamic simulation, inelastic neutron scattering, MOssbauer spectroscopy and spectral broadening analysis (b). (Likhtenshtein et al., 2000). Reproduced with permission.

CCD = charge-coupled device IHIs = interligand hypervalent interactions ILL = Institut Lane-Langevin INS = inelastic neutron scattering IPNS = intense pulsed neutron source LINAC = linear accelerator MaNDi=macro-molecular neutron diffractometer NiMH=nickel-metal OPAL = open pool Australian light-water reactor hydride SANS = small-angle neutron scattering SNS = spallation neutron source. 

The picosecond internal dynamics of myoglobin was explored by measuring inelastic neutron scattering by Smith et al. [25]. At low temperatures they found the dynamics to be harmonic while at higher temperatures a considerable quasielastic scattering was detected. Agreement between the experimentally observed spectra and that calculated from molecular dynamics simulations also showed evidence for restriction of the conformational space sampled at 80 K relative to 300 K. On the basis of these results it was concluded that the protein is trapped in local minima at low temperatures in accord with the multiple substate model suggested by low temperature flash photolysis experiments and previous molecular dynamics simulations. Comparison of atomic fluctuation data sets collected at both 325 K and 80 K confirms that the room temperature... 

Chapter 12. Interpretation of inelastic neutron scattering spectra for water ice by lattice and molecular dynamic simulations 471... 

C. K. Loong et ai, High-Energy Oxygen Phonon Modes and Superconductivity in Bai j,Kj,Bi03 An Inelastic-Neutron-Scattering Experiment and Molecular-Dynamics Simulation, Phys. Rev. Lett. 62, 2628-2631 (1989). 

Inelastic neutron scattering (INS) is suitable to detect librations, low-energy rotational motions in solids. It was used to follow molecular reorientations as a function of temperature [25]. These reorientations should not be confused with pseudorotation as they involve actual displacements of atoms in the crystal they correspond to an abrupt change in the crystal field [4] and their intensity scales with the crystal field strength. 

Schimmel et al. [63] have conducted adsorption isotherm and inelastic neutron scattering studies of hydrogen adsorbed on various carbon adsorbents including SWNTs. By comparing the inelastic neutron scattering results for Hj on the SWNTs with those for interstitially loaded H2 on Cgg, they conclude that H2 cannot adsorb in the ICs of SWNTs. They explain that this occurs because the molecular size of H2 is too large to fit in the estimated size for the ICs. 

A.J. Ramirez-Cuesta, P.C.H. Mitchell, S.F. Parker P.M Rodger (1999). Phys. Chem. Chem, Phys., 1, 5711-5715. Dynamics of water and template molecules in the interlayer space of a layered aluminophosphate. Experimental inelastic neutron scattering spectra and molecular dynamics simulated spectra. 

J. Tomkinson (1988). Chem. Phys., 127, 445-449. The effect of recoil in the inelastic neutron scattering spectra of molecular vibrations. 

B.L. Mojet, J. Eckert, R.A. van Santen, A. Albinati R.E. Lechner (2001). J. Am. Chem. Soc., 123, 8147-8148. Evidence for chemisorbed molecular hydrogen in Fe-ZSM5 from inelastic neutron scattering. 

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