123 research outputs found
Two-photon decay in silver and hafnium atoms
The decay of silver and hafnium atoms with a vacancy in the K shell by the emission of photon pairs which continuously share the transition energy was studied. Radioactive decay of 109Cd and of 179Ta was used to generate K-shell vacancy states in silver and hafnium atoms, respectively. A pair of germanium detectors in a 180° geometry and a fast-slow coincidence system with a (128×512×512)-channel three-parameter pulse-height analyzer were used in the measurements. Two-dimensional spectra of numbers of events as functions of amplitudes of coincident pulses from the two detectors were analyzed. Surface fitting of two-dimensional spectra and curve fitting of sum spectra were applied to deduce the number of events. The differential transition probabilities of 2s→1s, 3s→1s, 3d→1s, and 4sd→1s two-photon decay per decay of a K-shell vacancy have been determined. For silver they are compared with the results of relativistic self-consistent-field calculations of Mu and Crasemann [Phys. Rev. A 38, 4585 (1988)] and of Tong, Li, Kissel, and Pratt [Phys. Rev. A 42, 1442 (1990)]. The results for silver and hafnium are compared with the results of nonrelativistic calculations for hydrogenic silver and hafnium ions. The 3d→1s two-photon decays show the resonance effect, in accordance with the theoretical predictions
Hypersatellite and satellite transitions in xenon atoms
Decay of double-K-shell-vacancy states in xenon atoms, created in the decay of 131Cs, was investigated. The measurements were performed with a pair of germanium detectors, a fast-slow coincidence system, and a three-parameter pulse-height analyzer. In the analysis of the two-dimensional E1-E2 spectrum, improved least-squares routines were applied
Hole-depletion of ladders in SrCuO induced by correlation effects
The hole distribution in SrCuO is studied by low
temperature polarization dependent O K Near-Edge X-ray Absorption Fine
Structure measurements and state of the art electronic structure calculations
that include core-hole and correlation effects in a mean-field approach.
Contrary to all previous analysis, based on semi-empirical models, we show that
correlations and antiferromagnetic ordering favor the strong chain
hole-attraction. For the remaining small number of holes accommodated on
ladders, leg-sites are preferred to rung-sites. The small hole affinity of
rung-sites explains naturally the 1D - 2D cross-over in the phase diagram of
(La,Y,Sr,Ca)CuOComment: 6 pages, 8 figure
Resonant inelastic x-ray scattering probes the electron-phonon coupling in the spin-liquid kappa-(BEDT-TTF)2Cu2(CN)3
Resonant inelastic x-ray scattering at the N K edge reveals clearly resolved
harmonics of the anion plane vibrations in the kappa-(BEDT-TTF)2Cu2(CN)3
spin-liquid insulator. Tuning the incoming light energy at the K edge of two
distinct N sites permits to excite different sets of phonon modes. Cyanide CN
stretching mode is selected at the edge of the ordered N sites which are more
strongly connected to the BEDT-TTF molecules, while positionally disordered N
sites show multi-mode excitation. Combining measurements with calculations on
an anion plane cluster permits to estimate the sitedependent electron-phonon
coupling of the modes related to nitrogen excitation
Covariant and Heavy Quark Symmetric Quark Models
There exist relativistic quark models (potential or MIT-bag) which satisfy
the heavy quark symmetry (HQS) relations among meson decay constants and form
factors. Covariant construction of the momentum eigenstates, developed here,
can correct for spurious center-of-mass motion contributions.Proton form factor
and M1 transitions in quarkonia are calculated. Explicit expression for the
Isgur-Wise function is found and model determined deviations from HQS are
studied. All results depend on the model parameters only. No additional ad hoc
assumptions are needed.Comment: 34 pages (2 figures not included but avaliable upon request), LATEX,
(to be published in Phys.Rev.D
Ground State of the Quasi-1D \bvs\ resolved by Resonant Magnetic X-ray Scattering
Resonant-magnetic x-ray scattering (RMXS) near the vanadium
-absorption edges has been used to investigate the low temperature
magnetic structure of high quality \bvs\ single crystals. Below = 31 K,
the strong resonance revealed a triple-incommensurate magnetic ordering at wave
vector (0.226 0.226 ) in the hexagonal notation, with = 0.033. The
simulations of the experimental RMXS spectra with a time-dependent density
functional theory indicate an antiferromagnetic order with the spins polarized
along in the monoclinic structure.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let
The ferroelectric Mott-Hubbard phase of organic (TMTTF)2X conductors
We present experimental evidences for a ferro-electric transition in the
family of quasi one- dimensional conductors (TMTTF)2X. We interpret this new
transition in the frame of the combined Mott-Hubbard state taking into account
the double action of the spontaneous charge disproportionation on the TMTTF
molecular stacks and of the X anionic potentials
Properties of the massive Thirring model from the XYZ spin chain
We consider here the massive Thirring model regularized with the XYZ spin
chain. We numerically calculate the mass ratios of particles which lie in the
discrete part of the spectrum and obtain results in accordance with the DHN
formula and in disagreement with recent calculations in the literature based on
the numerical Bethe ansatz and infinite momentum frame methods. We also analyze
the short distance behavior of these states and evaluate the conformal
dimensions. This paper, taken together with the previous one for the
sine-Gordon model, confirms the duality relation between two models formulated
by Klassen and Melzer [Int. J. Mod. Phys. A 8, 4131 (1993)].Comment: 11 pages, 6 figures, to be published in Phys. Rev. D 6
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