Neutron vibrational spectra

The calculations with empirical potentials of the structure and dynamics of paraffin molecules adsorbed on graphite are presently being extended (27) to include the intermolecular interaction. This work together with elastic neutron diffraction experiments on deuterated paraffin films (see Sec. Ill) should provide a sounder basis for interpreting the inelastic neutron vibrational spectra. 

D. Inelastic neutron spectroscopy applied to molecules chemisorbed on catalytic substrates, tne model system considered in the previous section is of interest in demonstrating the degree to which neutron vibrational spectra can be interpreted on a well-characterized substrate. Unfortunately from the standpoint of this symposium, the graphite substrates in these experiments are not chemically active. Therefore, in this section, we wish to... 

A more realistic analysis of the neutron vibrational spectra must include the intermolecular interactions present in the solid state. We now proceed to introduce these forces in a systematic manner. 

Before discussing the adsorbed butane vibrational spectrum, we first describe the inelastic neutron spectrometer used in this experiment. 

In the case of the ethane (45) and butane (46) monolayers adsorbed on graphite, it has been possible to analyze the neutron diffraction patterns using all three Euler angles of the molecule as orientational parameters. Here we limit discussion to the butane monolayer which we have taken as a model system and whose vibrational spectrum was discussed in Sec. II. 

Two of the more direct techniques used in the study of lattice dynamics of crystals have been the scattering of neutrons and of x-rays from crystals. In addition, the phonon vibrational spectrum can be inferred from careful analysis of measurements of specific heat and elastic constants. In studies of Bragg reflection of x-rays (which involves no loss of energy to the lattice), it was found that temperature has a strong influence on the intensity of the reflected lines. The intensity of the scattered x-rays as a function of temperature can be expressed by I (T) = IQ e"2Tr(r) where 2W(T) is called the Debye-Waller factor. Similarly in the Mossbauer effect, gamma rays are emitted or absorbed without loss of energy and without change in the quantum state of the lattice by... 

M. Plazanet, N. Fukushima, M.R. Johnson, A.J. Horsewill, H.P. Trommsdorff (2001). J. Chem. Phys., 115, 3241-3248 The vibrational spectrum of crystalline benzoic acid Inelastic neutron scattering and density functional theory calculations. H.B. Burgi S.C. Capelli (2000). Acta Cryst., A56 403-412. Dynamics of molecules in crystals from multi-temperature anisotropic displacement parameters. I Theory. 

The incident energy is selected stepwise across the spectrum and, since the final energy is fixed below 40 cm, the energy transfer is obtained. This is the working principle of the spectrometer INlBeF [16] at the ILL, which was, for many years, the best spectrometer for neutron vibrational speetroscopy. 

J. Eckert, C.E. Webster, M.B. Hall, A. Albinati L.M. Venanzi (2002). Inorg. Chim. Acta, 330, 240-249. The vibrational spectrum of Tp(3,5-Me)RhH2(H2)] a computational and inelastic neutron scattering study. 

J. Howard, T.C. Waddington C.J. Wright (1978). Chem. Phys. Lett., 56, 258-62. The vibrational spectrum of hydrogen adsorbed on palladium black measured using inelastic neutron scattering spectroscopy. 

S.F. Parker, P.H. Dallin, B.T. Keiller, C.E. Anson U.A. Jayasooriya (1999). Phys. Chem. Chem. Phys., 1,2589-2592. An inelastic neutron scattering study and re-assignment of the vibrational spectrum of [Os3(CO)9(p,2 CO)(ji3 tl C2H2)], a model compound for chemisorbed ethyne. 

E. Kemner, I.M. de Schepper, G.J. Kearley U.A. Jayasooriya (2000). J. Chem. Phys., 112, 10926-10929. The vibrational spectrum of solid ferrocene by inelastic neutron scattering. 

B.S. Hudson, D.A. Braden, S.F. Parker H. Prinzbach (2000). Angew. Chem. Int. Ed., 39, 514-516. The vibrationally inelastic neutron scattering spectrum of dodecahedrane Experiment and DFT simulation. 

Chem. Phys., 261, 239-247. Vibrational analysis of the inelastic neutron scattering spectrum of pyridine. 

A. Navarro, M. Femdndez-G6mez, J.J. L6pez-GonzdIez, M.P. Paz Femdndez-Liencres, E. Martinez-Torres, J. Tomkinson G.J. Kearley (1999). J. Phys. Chem. A. 103, 5833-5840. Inelastic neutron scattering spectrum and quantum mechanical calculations of the internal vibrations of pyrimidine. 

H.G. Schimmel, M.R. Johnson, G.J. Kearley, A.J. Ramirez-Cuesta, J. Huot F.M. Mulder (2004). Materials Science and Engineering B-Solid State Materials for Advanced Technology, 108, 38-41. The vibrational spectrum of magnesium hydride from inelastic neutron scattering and density functional theory. 

F. Partal, M. Femdndez-Gomez, JJ. L6pez-Gonz41ez, A. Navano GJ. Kearley (2000), Chem. Phys., 261, 239-247. Vibrational analysis of the inelastic neutron scattering spectrum of pyridine. 

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