Search results for "Ham"
showing 10 items of 2612 documents
Microscopic description of dissipative dynamics of a level-crossing transition
2011
We analyze the effect of a dissipative bosonic environment on the Landau-Zener-Stuckelberg-Majorana (LZSM) level crossing model by using a microscopic approach to derive the relevant master equation. For an environment at zero temperature and weak dissipation our microscopic approach confirms the independence of the survival probability on the decay rate that has been predicted earlier by the simple phenomenological LZSM model. For strong decay the microscopic approach predicts a notable increase of the survival probability, which signals dynamical decoupling of the initial state. Unlike the phenomenological model our approach makes it possible to study the dependence of the system dynamics…
Electric field controllable magnetic coupling of localized spins mediated by itinerant electrons: a toy model
2017
In this paper, we propose a toy model to describe the magnetic coupling between the localized spins mediated by the itinerant electron in partially delocalized mixed-valence (MV) systems. This minimal model takes into account the key interactions that are common for all such systems, namely, electron transfer in the valence-delocalized moiety and magnetic exchange between the localized spins and the delocalized electrons. The proposed descriptive model is exactly solvable which allows us to qualitatively and quantitatively discuss the main features of the whole class of partially delocalized MV systems. In the case of relatively strong exchange coupling, the combined action of these two int…
Simultaneous Determination of Force Constants and Dipole Moment Derivatives of Methane.
1998
The expressions of the effective Hamiltonian and dipole moment spectroscopic parameters in the tetrahedral formalism are used simultaneously to fit the force field and dipole moment derivatives of the methane molecule. Data, the so-called "observed parameters," are the values of the spectroscopic parameters determined from the frequencies and line strengths analyses. The ambiguities of most parameters (in the polyad scheme) are treated consistently with the Hamiltonian reduction chosen in the frequency analyses. As an illustration, the method is applied to the tetrahedral XY4 isotopic species only. The quadratic and cubic force field constants have been determined in addition to the linear …
Development of the Hamiltonian and transition moment operators of symmetric top molecules using the O(3)⊃C∞v⊃C3v group chain
2005
Abstract We present a development of the Hamiltonian, dipole moment, and polarizability operators for XY3Z molecules. These rovibrational operators are written with the aid of a tensorial formalism derived from the one already used in Dijon and adapted to the XY3Z symmetric tops in a recent paper [A. El Hilali, V. Boudon, M. Loete, J. Mol. Spectrosc. 234 (2005) 166–174]. We use the O (3) ⊃ C∞v ⊃ C3v group chain. Expressions for the matrix elements are derived for these operators.
Spectroscopy of XY5Z (C4v) Molecules: Development of the Hamiltonian and the Transition Moment Operators Using a Tensorial Formalism
2000
We present a development of the Hamiltonian, dipole moment, and polarizability operators of XY(5)Z (C(4v)) molecules using a tensorial formalism derived from the one developed previously in Dijon for XY(6) molecules. These operators are involved in the calculation of the energies and intensities of rovibrational transitions and are essential for spectrum simulations. Expressions for the matrix elements are derived for all these operators. Copyright 2000 Academic Press.
The Ramsey method in high-precision mass spectrometry with Penning traps: Theoretical foundations
2007
Abstract This paper presents in a quantum mechanical framework a theoretical description of the interconversion of the magnetron and modified cyclotron motional modes of ions in a Penning trap due to excitation by external rf-quadrupole fields with a frequency near the true cyclotron frequency. The work aims at a correct description of the resonance line shapes that are observed in connection with more complicated excitation schemes using several excitation pulses, such as Ramsey’s method of separated oscillating fields. Quantum mechanical arguments together with the “rotating wave approximation” suggest a model Hamiltonian that permits a rigorous solution of the corresponding Heisenberg eq…
A Symmetry Adapted Approach to the Dynamic Jahn-Teller Problem
2011
In this article we present a symmetry-adapted approach aimed to the accurate solution of the dynamic Jahn-Teller (JT) problem. The algorithm for the solution of the eigen-problem takes full advantage of the point symmetry arguments. The system under consideration is supposed to consist of a set of electronic levels \({\Gamma }_{1},{\Gamma }_{2}\ldots {\Gamma }_{n}\) labeled by the irreducible representations (irreps) of the actual point group, mixed by the active JT and pseudo JT vibrational modes \({\Gamma }_{1},{\Gamma }_{2}\ldots {\Gamma }_{f}\) (vibrational irreps). The bosonic creation operators b +(Γγ) are transformed as components γ of the vibrational irrep Γ. The first excited vibra…
The RICH counter in the CERN hyperon beam experiment
1992
Abstract The hyperon beam experiment WA89 at the CERN-SPS uses a ring imaging Cherenkov counter (RICH) for identification of secondaries from ∑ − N reactions. Cherenkov photons are generated in a 5 m long radiator volume filled with nitrogen at atmospheric pressure and detected in drift chambers. The drift chambers cover an active surface of 1.6 × 0.75 m 2 , with a maximum drift path of 41 cm. Photoelectrons are counted on 1280 wires with a pitch of 2.54 mm, equipped with multihit TDCs. The counting gas is ethane saturated with TMAE at 30°C. The counter was operated in two beam periods in 1990 and 1991. The spatial resolution of the chambers is better than 2 mm and under normal running cond…
Kohn–Sham energy decomposition for molecules in a magnetic field
2018
We study the total molecular electronic energy and its Kohn–Sham components within the framework of magnetic-field density-functional theory (BDFT), an alternative to current-dependent density-functional theory (CDFT) for molecules in the presence of magnetic fields. For a selection of closed-shell dia- and paramagnetic molecules, we investigate the dependence of the total electronic energy and its Kohn–Sham components on the magnetic field. Results obtained from commonly used density-functional approximations are compared with those obtained from Lieb optimizations based on magnetic-field dependent relaxed coupled-cluster singles-and-doubles (CCSD) and second-order Moller–Plesset (MP2) den…
Remarks on quadratic Hamiltonians in spaceflight mechanics
2006
A particular family of Hamiltonian functions is considered. Such functions are quadratic in the moment variables and arise in spaceflight mechanics when the averaged system of energy minimizing trajectories of the Kepler equation is computed. An important issue of perturbation theory and averaging is to provide integrable approximations of nonlinear systems. It turns out that such integrability properties hold here.