Search results for "Energy Levels"
showing 10 items of 245 documents
Orbital-selective Mott transitions in the 2-band J_z-model: a high-precision quantum Monte Carlo study
2005
Using high-precision quantum Monte Carlo (QMC) simulations within the framework of dynamical mean field theory (DMFT), we show that the anisotropic degenerate two-orbital Hubbard model contains two consecutive orbital-selective Mott transitions (OSMTs) even in the absence of spin-flip terms and pair-hopping processes. In order to reveal the second transition we carefully analyze the low-frequency part of the self-energy and the local spectral functions. This paper extends our previous work to lower temperatures. We discuss the nature - in particular the order - of both Mott transitions and list various possible extensions.
Controlled Observation of a Nonequilibrium Ising-Bloch Transition in a Nonlinear Optical Cavity
2004
We describe the controlled observation of the nonequilibrium Ising-Bloch transition in a broad area nonlinear optical cavity, namely, a quasi-1D single longitudinal-mode photorefractive oscilator in a degenerate four-wave mixing configuration. Our experimental technique allows for the controlled injection of the domain walls. We use cavity detuning as control parameter and find that both Ising and Bloch walls can exist for the same detuning values within a certain interval of detunings, i.e., the Ising-Bloch transition is hysteretic in our case. A complex Ginzburg-Landau model is used for supporting the observations.
On the theoretical analysis of the lowest many-electron states for cyclic zigzag graphene nano-ribbons
2014
We have calculated the optical and magnetic properties of the four lowest many-body states for cyclic zigzag graphene nano-ribbons (GNRs). The results have been obtained within the semi-empirical restricted frozen Hartree?Fock approximation. Firstly, we obtained one-determinant numerical and analytical coincident results. We detected the existence of two degenerate open-shell molecular orbitals (MOs) o, o?. Due to this degeneracy, some of the mentioned results do depend on any (arbitrary) orthogonal transformation between these two MOs. We have improved these preliminary results by using linear combinations of two determinants, which are eigenfunctions of the operators, which commute with t…
A Tensorial Formalism Adapted to the Rovibronic Couplings in the Colored Hexafluorides: Application to the nu(5)(F(2g)) and nu(3)(F(1u)) Modes.
2000
A tensorial formalism adapted to the case of transition-metal hexafluorides in a degenerate electronic state has been developed on the basis of preceding works about spherical-top molecules in a nondegenerate electronic state. We have introduced electronic operators constructed using group theory features and some physical considerations. Vibronic couplings (Jahn-Teller effect, etc.) have been reviewed for the triply degenerate vibrational modes nu(5)(F(2g)) and nu(3)(F(1u)) leading to the identification of the main vibronic parameters. For the first time, an effective rovibronic Hamiltonian as well as the effective transition moment operators (dipole moment and polarizability) for rovibron…
Electron Capture Processes in Intermediate Mass stars
2015
Intermediate mass stars develop a degenerate core constituted of O, Ne and Mg during their evolution. As the density in the core increases electron capture sets in igniting Ne and O burning. Particularly important is electron capture on 20Ne that has been found recently to be dominated by a second forbidden transition from the 0+ ground state of 20Ne to the 2+ ground state of 20F. We have performed shell–model calculations to determine the transition strength and provide an updated value of the electron capture rate and the expected branching ratio to the corresponding β–decay process. peerReviewed
Isomer Spectroscopy in90216Th126and the Magicity of92218U126
2001
Excited states in (216)Th were investigated via prompt and delayed gamma decays and the recoil-decay tagging method. The decay schemes of the I(pi) = (8+), t(1/2) = 128(8) micros, the I(pi) = (11-), t(1/2) = 615(55) ns, and the I(pi) = (14+), t(1/2) > or = 130 ns isomers were established. The configuration pi h(9/2)f(7/2) is assigned to the I(pi) = (8+) isomer, which implies that the h(9/2) and f(7/2) states are nearly degenerate. This is ascribed to increased binding of the f(7/2) orbital by its coupling to a low-lying I(pi) = (3-) state at E(x) = 1687 keV. The role of octupole and pairing correlations for a Z = 92 shell closure prediction is discussed on the basis of shell model calculati…
Calculations of Stark-broadened line shapes in phase-conjugate degenerate four-wave mixing laser spectroscopy
2005
The Stark-broadened line shapes for phase-conjugate degenerate four-wave mixing (PCDFWM) laser spectroscopy are studied. The line profiles are calculated for high-density $({N}_{e}g{10}^{21}\phantom{\rule{0.3em}{0ex}}{\mathrm{m}}^{\ensuremath{-}3})$ plasma conditions and for different contributions of the Doppler broadening. Calculations are performed in the limit of low laser intensities using the perturbation approach. The theoretical model takes into account the Stark effect together with the ion dynamics, the electron collisions, and the Doppler effect. The resultant PCDFWM spectral profiles are significantly less broadened and less asymmetric than the emission profiles but shifted by s…
The algebra eigenstates method for some systems with spin-like interactions
2006
International audience; An extension of the algebra eigenstates formalism is proposed to solve the eigenvalue equation for a class of problems involving "spin interactions". The method is detailed for the harmonic oscillator, su(2) and su(1, 1) algebras. Special emphasis is given to the resolution of problems in vibronic spectroscopy involving doubly degenerate electronic states.
Multiphase patterns in a degenerate nonlinear oscillator
2017
Degenerate four-wave mixing (DFWM) oscillators are phase-bistable devices. In such systems, two equivalent states, of equal intensities but opposite phases can be generated. When the cavity Fresnel number is large, different regions of the beam transverse section can have different phases, leading to phase patterns like phase fronts (or domain walls), i.e. ID structures separating regions with opposite phase that manifest as dark lines (as the phase jumps by π across the wall), phase domains, and phase solitons, among others.
Analysis of the "Unusual" Vibrational Components of Triply Degenerate Vibrational Mode nu(6) of Mo(CO)(6) Based on the Classical Interpretation of th…
2001
Rotational structure of the triply degenerate vibrational state nu(6)(F(1u)) of the octahedral molecule Mo(CO)(6) is analyzed qualitatively on the basis of classical mechanics. We show that the energy level redistribution between the vibrational components of nu(6)(F(1u)) occurs due to rotational excitation and is related to the formation of singular points of classical rotational energy surfaces. The singularity is stable under small variations of parameters of the effective rovibrational Hamiltonian. Parameters responsible for the persistence of this phenomenon are specified. Comparison with quantum calculations demonstrates the high qualitative and quantitative accuracy of our classical …