Relaxation (NMR)

About: Relaxation (NMR) is a research topic. Over the lifetime, 29342 publications have been published within this topic receiving 689851 citations.

Progress in the non-equilibrium vibrational kinetics of hydrogen in magnetic multicusp H - ion sources

Abstract: The non-equilibrium vibrational kinetics of H 2 in multicusp magnetic discharges has been studied by improving a previous model developed by our groups. In particular, a complete set of V-T (vibrational translation) rates involving H-H 2 ( v ) collisions, calculated by using a three-dimensional dynamics approach, has been inserted into our self-consistent model for better representing the corresponding relaxation. Different experimental situations are simulated with special emphasis on the temporal scales necessary for the different distributions (electron energy and vibrational distributions) to reach stationary values. Finally, a comparison between theoretical and experimental quantities such as vibrational temperature, electron temperature, electron number density and concentration of negative ions (H − ) shows a satisfactory agreement, thus indicating the basic correctness of our model.

Modifying the properties of 4f single-ion magnets by peripheral ligand functionalisation

Abstract: We study the ligand-field splittings and magnetic properties of three ErIII single-ion magnets which differ in the peripheral ligand sphere but exhibit similar first coordination spheres by inelastic neutron scattering (INS) and SQUID magnetometry. The INS spectra of the three compounds are profoundly different pointing at a strong response of the magnetic behavior to minor structural changes, as they are e.g. encountered when depositing molecules on surfaces. The observation of several magnetic excitations within the J = 15/2 ground multiplet together with single-crystal magnetic measurements allows for the extraction of the sign and magnitude of all symmetry-allowed Stevens parameters. The parameter values and the energy spectrum derived from INS are compared to the results of state-of-the-art ab initio CASSCF calculations. Temperature-dependent alternating current (ac) susceptibility measurements suggest that the magnetisation relaxation in the investigated temperature range of 1.9 K < T < 5 K is dominated by quantum tunnelling of magnetisation and two-phonon Raman processes. The possibility of observing electron paramagnetic resonance transitions between the ground-state doublet states, which can be suppressed in perfectly axial single-ion magnets, renders the studied systems interesting as representations of quantum bits.

Time-resolved two-photon photoemission from Cu(100): Energy dependence of electron relaxation.

Abstract: A time-domain measurement of the relaxation time of photoexcited electrons as a function of excitation energy at a single-crystal Cu(100) surface has been made with time-resolved two-photon photoemission. The relaxation lifetime of the excited electrons is found to decrease rapidly with the amount of excitation energy above the Fermi level, and we compare the measured lifetimes with a calculation based on Fermi-liquid theory. The results reveal a qualitative agreement with the theory, and indicate that effects due to transport of the electrons away from the surface and into the bulk are important.

Dipolar interactions in two- and three-dimensional magnetic nanoparticle arrays

Abstract: Uniform, organically functionalized, 8.5-nm-diameter nanocrystals of ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$ were synthesized and assembled into close-packed monolayer as well as multilayer arrays using the Langmuir-Blodgett technique. The ac and dc magnetic susceptibility measurements on arrays in comparison with isolated particles indicate strong dipolar interactions and a spin-glass-like slowing down of relaxation times. Differences in magnetic characteristics between monolayer to multilayer arrays were observed, such as larger remanent magnetization and a higher blocking temperature in the two-dimensional system.