J. Wuttke

FAST RELAXATION IN A FRAGILE LIQUID UNDER PRESSURE

The incoherent dynamic structure factor of ortho-terphenyl has been measured by neutron time-of-flight and backscattering technique in the pressure range from 0.1 MPa to 240 MPa for temperatures between 301 K and 335 K. Tagged-particle correlations in the compressed liquid decay in two steps. The alpha-relaxation lineshape is independent of pressure, and the relaxation time proportional to viscosity. A kink in the amplitude f_Q(P) reveals the onset of beta relaxation. The beta-relaxation regime can be described by the mode-coupling scaling function; amplitudes and time scales allow a consistent determination of the critical pressure P_c(T). alpha and beta relaxation depend in the same way on the thermodynamic state; close to the mode-coupling cross-over, this dependence can be parametrised by an effective coupling Gamma ~ n*T**{-1/4}.

Prospects of resonance spin echo

Abstract We want to review the applications of high-frequency-flippers in neutron spin echo and related fields: Two separated flippers of this type can replace a homogenous static magnetic field in a spin-echo spectrometer. We describe the spin-echo instruments at Saclay and Berlin relying on such flippers and present some measurements. By tilting these coils with respect to the beam axis, one can determine line widths of phonons with unprecedented precision. First experiments are shown. With two flippers driven at different frequencies one can realise an instrument (“MIEZE”), where the intensity at the detector is modulated with a frequency up to several MHz. Its use for high-resolution quasielastic scattering from protonated samples is demonstrated. The high-frequency signal may be used for “neutron computer holography” – we discuss a possible realisation.

Propylene carbonate reexamined: Mode-couplingβscaling without factorization?

The dynamic susceptibility of propylene carbonate in the moderately viscous regime above

Brillouin-scattering study of propylene carbonate: An evaluation of phenomenological and mode coupling analyses

T_{\rm c}

Vibrational states of glassy and crystalline orthoterphenyl

is reinvestigated by incoherent neutron and depolarised light scattering, and compared to dielectric loss and solvation response. Depending on the strength of

Wavenumber dependence of structural \(\) relaxation in a molecular liquid

\alpha

Calcium rubidium nitrate: mode-coupling beta scaling without factorization.

relaxation, a more or less extended

Improved sample holder for multidetector neutron spectrometers

\beta

Two-step relaxation in a viscous metallic liquid

scaling regime is found. Mode-coupling fits yield consistently

Self-absorption coefficient for tubular samples: – Erratum and Addendum to Physica B 266 (1999) 112

\lambda=0.72