715 research outputs found
Analyses of pyrimidine and purine bases by a combination of paper chromatography and time of flight mass spectrometry
Paper chromatography and mass spectrometry for analyses of pyrimidine and purine base
Electric Dipolar Susceptibility of the Anderson-Holstein Model
The temperature dependence of electric dipolar susceptibility \chi_P is
discussed on the basis of the Anderson-Holstein model with the use of a
numerical renormalization group (NRG) technique. Note that P is related with
phonon Green's function D. In order to obtain correct temperature dependence of
P at low temperatures, we propose a method to evaluate P through the Dyson
equation from charge susceptibility \chi_c calculated by the NRG, in contrast
to the direct NRG calculation of D. We find that the irreducible charge
susceptibility estimated from \chi_c agree with the perturbation calculation,
suggesting that our method works well.Comment: 4 pages, 4 figure
Pressure-tuning of the c-f hybridization in Yb metal detected by infrared spectroscopy up to 18 GPa
It has been known that the elemental Yb, a divalent metal at mbient pressure,
becomes a mixed-valent metal under external pressure, with its valence reaching
~2.6 at 30 GPa. In this work, infrared spectroscopy has been used to probe the
evolution of microscopic electronic states associated with the valence
crossover in Yb at external pressures up to 18 GPa. The measured infrared
reflectivity spectrum R(w) of Yb has shown large variations with pressure. In
particular, R(w) develops a deep minimum in the mid-infrared, which shifts to
lower energy with increasing pressure. The dip is attributed to optical
absorption due to a conduction c-f electron hybridization state, similarly to
those previously observed for heavy fermion compounds. The red shift of the dip
indicates that the - hybridization decreases with pressure, which is
consistent with the increase of valence.Comment: 2 pages, to appear in J. Phys. Soc. Jpn. Supp
Superconductor-insulator transition in nanowires and nanowire arrays
Superconducting nanowires are the dual elements to Josephson junctions, with
quantum phase-slip processes replacing the tunneling of Cooper pairs. When the
quantum phase-slip amplitude ES is much smaller than the inductive energy EL,
the nanowire responds as a superconducting inductor. When the inductive energy
is small, the response is capacitive. The crossover at low temperatures as a
function of ES/EL is discussed and compared with earlier experimental results.
For one-dimensional and two-dimensional arrays of nanowires quantum phase
transitions are expected as a function of ES/EL. They can be tuned by a
homogeneous magnetic frustration.Comment: 15 pages, 10 figure
Consistency of Lambda-Lambda hypernuclear events
Highlights of Lambda-Lambda emulsion events are briefly reviewed. Given three
accepted events, shell-model predictions based on p-shell Lambda hypernuclear
spectroscopic studies are shown to reproduce the Lambda-Lambda (LL) binding
energies of LL10Be and LL13B in terms of the LL binding energy of LL6He.
Predictions for other species offer judgement on several alternative
assignments of the LL13B KEK-E176 event, and on the assignments LL11Be and
LL12Be suggested recently for the KEK-E373 HIDA event. The predictions of the
shell model, spanning a wide range of A values, are compared with those of
cluster models, where the latter are available.Comment: Based on talk given by Avraham Gal at EXA 2011, Vienna, September
2011; Proceedings version prepared for the journal Hyperfine Interactions;
v2--slight changes, matches published versio
Faddeev calculations for the A=5,6 Lambda-Lambda hypernuclei
Faddev calculations are reported for Lambda-Lambda-5H, Lambda-Lambda-5He and
Lambda-Lambda-6He in terms of two Lambda hyperons plus the respective nuclear
clusters, using Lambda-Lambda central potentials considered in past non-Faddeev
calculations of Lambda-Lambda-6He. The convergence with respect to the
partial-wave expansion is studied, and comparison is made with some of these
Lambda-Lambda hypernuclear calculations. The Lambda-Lambda Xi-N mixing
effect is briefly discussed.Comment: submitted for publicatio
Measurement of the decay width of He
We have precisely measured decay width of \5LHe and
demonstrated significantly larger - overlap than expected
from the central repulsion - potential, which is derived from
YNG \Lambda$-nucleon interaction.Comment: 4 pages, 3 figure
Heavy-Electron Formation and Bipolaronic Transition in the Anharmonic Holstein Model
The emergence of the bipolaronic phase and the formation of the
heavy-electron state in the anharmonic Holstein model are investigated using
the dynamical mean-field theory in combination with the exact diagonalization
method. For a weak anharmonicity, it is confirmed that the first-order
polaron-bipolaron transition occurs from the observation of a discontinuity in
the behavior of several physical quantities. When the anharmonicity is
gradually increased, the polaron-bipolaron transition temperature is reduced as
well as the critical values of the electron-phonon coupling constant for
polaron-bipolaron transition. For a strong anharmonicity, the polaron-bipolaron
transition eventually changes to a crossover behavior. The effect of
anharmonicity on the formation of the heavy-electron state near the
polaron-bipolaron transition and the crossover region is discussed in detail.Comment: 11 pages, 13 figure
Resonant State in Helium-4 Lambda
In a recent experiment E906 at the BNL-AGS, a search for light S=-2
hypernuclei, strong evidence was found for the nuclide Hydrogen-4 double
Lambda. One of the most striking components of this data was the appearance of
a narrow low-momentum pi- line at k(pi-) = 104-105 MeV/c. This was ascribed to
the decay of Hydrogen-4 double Lambda into a resonant state in Helium-4 Lambda.
The existence of such a state is shown to be plausible and its characteristics
are delineated.Comment: 4 pages, 1 figur
Strong-Coupling Theory of Rattling-Induced Superconductivity
In order to clarify the mechanism of the enhancement of superconducting
transition temperature due to anharmonic local oscillation of a
guest ion in a cage composed of host atoms, i.e., {\it rattling}, we analyze
the anharmonic Holstein model by applying the Migdal-Eliashberg theory. From
the evaluation of the normal-state electron-phonon coupling constant, it is
found that the strong coupling state is developed, when the bottom of a
potential for the guest ion becomes wide and flat. Then, is
enhanced with the increase of the anharmonicity in the potential, although
is rather decreased when the potential becomes a double-well type
due to very strong anharmonicity. From these results, we propose a scenario of
anharmonicity-controlled strong-coupling tendency for superconductivity induced
by rattling. We briefly discuss possible relevance of the present scenario with
superconductivity in -pyrochlore oxides.Comment: 8 pages, 6 figure
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