Inelastic neutron scattering temperature dependence

Also known for some time is a phase transition at low temperature (111K), observed in studies with various methods (NQR, elasticity measurement by ultrasound, Raman spectrometry) 112 temperature-dependent neutron diffraction showed the phase transition to be caused by an antiphase rotation of adjacent anions around the threefold axis ([111] in the cubic cell) and to lower the symmetry from cubic to rhombohedral (Ric). As shown by inelastic neutron scattering, this phase transition is driven by a low-frequency rotatory soft mode (0.288 THz 9.61 cm / 298 K) 113 a more recent NQR study revealed a small hysteresis and hence first-order character of this transition.114 This rhombohedral structure is adopted by Rb2Hg(CN)4 already at room temperature (rav(Hg—C) 218.6, rav(C—N) 114.0 pm for two independent cyano groups), and the analogous phase transition to the cubic structure occurs at 398 K.115... 

The phonon branch that is suspected to interact strongly with the charge by the ARPES measurement, namely the zone-boundary Cu-0 bondstretching LO phonon branch (Fig. 1), was found by inelastic neutron scattering to show unusual temperature dependence [8],... 

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.

M. Barthes, H.N. Bordallo, J. Eckert, O. Maurus, G. de Nunzio J. L6on (1998). J. Phys. Chem. B, 6177-6183. Dynamics of crystalline N-methylacetamide Temperature dependence on infrared and inelastic neutron scattering spectra. 

For the experimental determination of the phonon dispersion relations S2(K), inelastic neutron scattering is by far the most powerful method, but it also requires the most effort Important complements to this method are however Raman scattering of light and infrared absorption spectroscopy. In particular, Raman scattering permits a precise determination of the frequencies of the Raman-active optical phonons with wavevectors K 0. It is thus particularly well suited to the evaluation of pressure and temperature dependences, which are especially prominent in the case of the soft organic molecular crystals. 

First we discuss the magnetic properties. Inelastic neutron scattering experiments to study the temperature dependence of the magnetic response of CeSnj have been... 

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