Electron Spin-Lattice Relaxation of doped Yb3+ ions in YBa2Cu3Ox

The electron spin-lattice relaxation (SLR) times T1 of Yb3+‡ ions were measured from the temperature dependence of electron spin resonance linewidth in Y0.99Yb0.01Ba2Cu3Ox with different oxygen contents. Raman relaxation processes dominate the electron SLR. Derived from the temperature dependence of the SLR rate, the Debye temperature (Td) increases with the critical temperature Tc and oxygen content x. Keywords: EPR; ESR; Electron spin-lattice relaxation; Debye temperature; Critical temperatureComment: 5 Pages 4 Figure

Spin-hybrid-phonon resonance in anisotropic quantum dots

We have studied the absorption of electromagnetic radiation of an anisotropic quantum dot taking into account the spin-flip processes that is associated with the interaction of the electrons with optical phonons. It is shown that these processes lead to the resonance absorption. Explicit formula is derived for the absorption coefficient. The positions of the resonances peaks are found

Energy scales and magnetoresistance at a quantum critical point

The magnetoresistance (MR) of CeCoIn_5 is notably different from that in many conventional metals. We show that a pronounced crossover from negative to positive MR at elevated temperatures and fixed magnetic fields is determined by the scaling behavior of quasiparticle effective mass. At a quantum critical point (QCP) this dependence generates kinks (crossover points from fast to slow growth) in thermodynamic characteristics (like specific heat, magnetization etc) at some temperatures when a strongly correlated electron system transits from the magnetic field induced Landau Fermi liquid (LFL) regime to the non-Fermi liquid (NFL) one taking place at rising temperatures. We show that the above kink-like peculiarity separates two distinct energy scales in QCP vicinity - low temperature LFL scale and high temperature one related to NFL regime. Our comprehensive theoretical analysis of experimental data permits to reveal for the first time new MR and kinks scaling behavior as well as to identify the physical reasons for above energy scales.Comment: 7 pages, 6 figure

Helium Clustering in Neutron-Rich Be Isotopes

Measurements of the helium-cluster breakup and neutron removal cross sections for neutron-rich Be isotopes A=10-12,14 are presented. These have been studied in the 30 to 42 MeV/u energy range where reaction measurements are proposed to be sensitive to the cluster content of the ground-state wave-function. These measurements provide a comprehensive survey of the decay processes of the Be isotopes by which the valence neutrons are removed revealing the underlying alpha-alpha core-cluster structure. The measurements indicate that clustering in the Be isotopes remains important up to the drip-line nucleus 14^Be and that the dominant helium-cluster structure in the neutron-rich Be isotopes corresponds to alpha-Xn-alpha.Comment: 5 pages, 2 tables and 3 figure

Voronoi-Delaunay analysis of normal modes in a simple model glass

We combine a conventional harmonic analysis of vibrations in a one-atomic model glass of soft spheres with a Voronoi-Delaunay geometrical analysis of the structure. ``Structure potentials'' (tetragonality, sphericity or perfectness) are introduced to describe the shape of the local atomic configurations (Delaunay simplices) as function of the atomic coordinates. Apart from the highest and lowest frequencies the amplitude weighted ``structure potential'' varies only little with frequency. The movement of atoms in soft modes causes transitions between different ``perfect'' realizations of local structure. As for the potential energy a dynamic matrix can be defined for the ``structure potential''. Its expectation value with respect to the vibrational modes increases nearly linearly with frequency and shows a clear indication of the boson peak. The structure eigenvectors of this dynamical matrix are strongly correlated to the vibrational ones. Four subgroups of modes can be distinguished

Access to resonant states in (24)Mg using the (12)C((13)C,(4)He+(20)Ne)n reaction

A study of the (12)C((13)C,(20)Ne+alpha)n reaction has been performed at (13)C beam energies of 12.0, 13.5 and 20.0 MeV. The measurements were to explore the extent to which (24)Mg excited states could be populated in a quasi-free (12)C+(12)C ->(20)Ne+alpha reaction in which the last neutron in the (13)C beam acts as a spectator. Excited states in (24)Mg are found at 13.25 (0.20) and 14.25 (0.20) MeV. These states are found to be produced from the neutron evaporation from the (25)Mg compound nucleus. The kinematic region associated with the quasi-free condition is dominated by contaminants from the reactions associated with neutron decay of excited states in (21)Ne populated in the (12)C((13)C,(21)Ne)alpha reaction

Neutron decay of excited states in 21Ne populated in the 12C(13C,21Ne)4He reaction

International audienceThe 12C(13C,α)21Ne reaction has been measured with a 13C beam energy of 20 MeV. States in 21Ne have been populated between 0 and 12 MeV with a resolution of ~350 keV (FWHM). A coincidence experiment has been performed in which either the bound 21Ne nucleus or the 20Ne nucleus produced via neutron decay is detected. This permitted the 21Ne states undergoing gamma decay and neutron decay to the ground and first excited states in 20Ne to be determined. The current measurements suggest several errors in the current compilation for 21Ne

8^{8}Be + 14^{14}C break-up of 22^{22}Ne

The $^{12}$C($^{18}$O, $^{14}$C + $^{8}$Be)$^{8}$Be reaction was studied at a beam energy of 140 MeV. Two multi-element charged-particle telescopes were used to detect the decay of $^{22}$Ne states into $^{14}$C + $^{8}$Be. The reconstructed excitation energy spectrum indicates that two states at 24.14(20) and 26.89(20) MeV decay by $^{8}Be emission. These states may be linked to a$^{14}$C + 2$\alpha$cluster structure in$^{22}$Ne

alpha : 2n : alpha Molecular Band in Be-10

The 10.15 MeV resonance in $^{10}$Be has been probed via resonant $^{6}$He+$^{4}$He elastic scattering. It is demonstrated that it is the J$^{p}$i=4$^{+}$ member of a rotational band built on the 6.18 MeV 0$^{+ }$state. A Gammaalpha of 0.10–0.13 MeV and Gammaalpha/Gamma=0.35–0.46 were deduced. The corresponding reduced alpha width, gammaalpha2, indicates one of the largest alpha-cluster spectroscopic factors known. The deformation of the band, including the 7.54 MeV, 2$^{+}$ member, is large ([h-bar]2/2I=200 keV). Such a deformation and the significant degree of clusterization signals a well-developed alpha:2n:alpha molecular structure