Search results for "Relaxation rate"
showing 10 items of 10 documents
Low-temperature microwave response of heavy-fermion compounds
2009
The electrodynamic properties of heavy fermions are distinct from those of normal metals due to the reduced transport relaxation rate that goes hand in hand with the enhanced mass. Using broadband microwave spectroscopy on thin-film samples of the heavy-fermion materials UPd2Al3 and UNi2Al3, we find that the frequency-dependent conductivity of these compounds at low temperatures follows a simple Drude prediction. The observed relaxation rates in the GHz frequency range are extremely low for a metal.
Investigating Intermolecular Interactions in a DME-Based Hybrid Ionic Liquid Electrolyte by HOESY NMR
2019
The intermolecular interactions in a hybrid electrolyte based on various compositions of the ionic liquid N-methyl-N-propyl pyrrolidinium bis-fluorosulfonylimide (C3mpyrFSI), LiFSI salt and an ether-based additive, 1,2-dimethoxy ethane (DME), have been investigated using the HOESY (Heteronuclear Overhauser Effect SpectroscopY) NMR experiment. This NMR technique allows a quantification of the intermolecular interactions in ionic liquids (ILs) by measuring the cross-relaxation rate (σ) between different pairs of nuclei. Thereby, we compare the cross-relaxation rates between the cations, anions and DME in these hybrid electrolyte systems using 1H-7Li and 1H-19F HOESY experiments, and interpret…
Quantum Tunneling of Magnetization under Pressure in the High-Spin Mn12 Molecular System
2004
Experimental and theoretical investigations of quantum tunneling magnetization in the high-spin cluster [Mn 1 2 O 1 2 (CH 3 COO) 1 6 (H 2 O) 4 ].2CH 3 COOH.4H 2 O under pressure have been performed. The main observation is that the blocking temperature and hysteresis width decrease under the effect of pressure. However, the position of the steps in the magnetization versus field curve does not change noticeably as pressure increases. A theoretical examination of the pressure influence on the relaxation rate and magnetization has been carried out taking into consideration the quantum tunneling effects. The qualitative agreement between theory and experiment has been achieved both at atmosphe…
Mössbauer effect study of the temperature and pressure dependence of the singlet-quintet intersystem crossing dynamics in an iron(II) spin crossover …
1988
The lineshapes of Mossbauer spectra of the iron(II) spin crossover complex [Fe(6-mepy)3 tren] (PF6)2 are affected by the dynamics of the HS⇌LS equilibrium. The lineshapes are reproduced with a stochastic two-state-relaxation-model yielding rate constants similar to those determined for related complexes in solution. Application of an external pressure of 150 MPa increases the relaxation rate.
Quantitative modeling of spin relaxation in quantum dots
2011
Physics Department, Harvard University, 02138 Cambridge MA, USA(Dated: December 16, 2011)We use numerically exact diagonalization to calculate the spin-orbit and phonon-induced triplet-singlet relaxation rate in a two-electron quantum dot exposed to a tilted magnetic field. Our schemeincludes a three-dimensional description of the quantum dot, the Rashba and the linear and cubicDresselhaus spin-orbit coupling, the ellipticity of the quantum dot, and the full angular descriptionof the magnetic field. We are able to find reasonable agreement with the experimental results ofMeunier et al. [Phys. Rev. Lett. 98, 126601 (2007)] in terms of the singlet-triplet energy splittingand the spin relaxation …
Dynamics of heavy fermions: Drude response in and
2006
While the effective mass of heavy fermions governs their thermodynamics, the optical properties are dominated by the characteristic relaxation rate which is expected to scale inversely with the effective mass. At the relaxation rate clear features, the so-called Drude response occur in the real and imaginary parts of the complex conductivity. Conventional optical spectroscopy can only indirectly probe the Drude response; thus we use novel broadband microwave spectroscopy to directly measure the frequency-dependent conductivity of UPd2Al3 and UNi2Al3 in the relevant frequency range and unambiguously observe the full low-energy electrodynamics of the heavy fermions including the Drude respons…
Frequency-dependent relaxation rate in superconductingYBa2Cu3O6+δ
2000
The submillimeter-wave $3 {\mathrm{cm}}^{\ensuremath{-}1}l\ensuremath{\nu}l40 {\mathrm{cm}}^{\ensuremath{-}1}$ complex conductivity of the reduced ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6+\ensuremath{\delta}}$ film ${(T}_{C}=56.5 \mathrm{K})$ was investigated for temperatures $4 \mathrm{K}lTl300 \mathrm{K}$ and compared to the properties of the same film in the optimally doped state. The frequency dependence of the effective quasiparticle scattering rate $1/{\ensuremath{\tau}}^{*}(\ensuremath{\nu})$ was extracted from the spectra. $1/{\ensuremath{\tau}}^{*}$ is shown to be frequency independent at low frequencies and high temperatures. A gradual change to $1/{\ensuremath{\tau}}^{…
NMR relaxation times of trabecular bone—reproducibility, relationships to tissue structure and effects of sample freezing
2010
Nuclear magnetic resonance (NMR) spectroscopy provides a potential tool for non-invasive evaluation of the trabecular bone structure. The objective of this study was to determine the reproducibility of the NMR relaxation parameters (T(2), Carr-Purcel-T(2), T(1ρ)) for fat and water and relate those to the structural parameters obtained by micro-computed tomography (μCT). Especially, we aimed to evaluate the effect of freezing on the relaxation parameters. For storing bone samples, freezing is the standard procedure during which the biochemical and cellular organization of the bone marrow may be affected. Bovine trabecular bone samples were stored at -20 °C for 7 days and measured by NMR spec…
Data from: Noninvasive assessment of respiratory muscle strength and activity in Myotonic dystrophy
2018
Objective To evaluate sensitivity/specificity of the maximum relaxation rate (MRR) of inspiratory muscles, amplitude of electromyographic activity of the sternocleidomastoid (SCM), scalene (SCA), parasternal (2ndIS) and rectus abdominis (RA) muscles; lung function and respiratory muscle strength in subjects with Myotonic dystrophy type 1 (DM1) compared with healthy subjects. Design and methods Quasi-experimental observational study with control group. MRR of inspiratory muscles, lung function and amplitude of the electromyographic activity of SCM, SCA, 2ndIS and RA muscles during maximum inspiratory pressure (PImax), maximum expiratory pressure (PEmax) and sniff nasal inspiratory pressure (…