Search results for "Names"
showing 10 items of 6843 documents
The bound state in the spectrum of the Lee–Friedrichs Hamiltonian
2000
Abstract The spectrum of the Lee–Friedrichs Hamiltonian, describing a two-level system embedded in a continuum, is considered. An appropriate discretization of the field modes is performed before taking the continuum limit. It is shown that the existence of an eigenstate with negative energy (bound state) is related to the nonanalyticity of the Friedrichs spectral representation. This negative energy state is a dressed state and its physical properties are studied in some significant cases.
Spin Transition in Iron Compounds
1984
First-row transition metal complexes with d4 up to d7 electron configuration in octahedral ligand fields (and d8 electron configuration in six-coordinate complexes of lower symmetry) may undergo temperature dependent high spin (HS) ⇌ low spin (LS) transition, provided the ligand field strength (Δ), including low symmetry contributions, becomes comparable in magnitude with the mean spin pairing energy (P). At a critical field strength Δcrit = P, the energy levels of the two spin states cross. This is illustrated in Fig. 1, where a simplified Tanabe-Sugano type energy level diagram for d6 systems (e.g. Fe2+, Co3+) is shown as an example. For weak ligand fields, Δ Δcrit, the LS state1A1g(Oh) b…
Measurements and calculations of Stark broadening parameters for the N I multiplet (1D)3s2D–(1D)3p2Do
2014
Calculations of line broadening parameters of a doubly excited N I transition, based on atomic structure data (taken from the literature), are reported. The obtained results were used for a critical analysis of formerly published experimental data, based on spectra measured in our laboratory. These measured spectra were then again analyzed and new broadening parameters were determined and compared with results of calculations.
Ionization energy ofLi6,7determined by triple-resonance laser spectroscopy
2007
Rydberg level energies for $^{7}\mathrm{Li}$ were measured using triple-resonance laser excitation, followed by drifted field ionization. In addition to the principal $n\phantom{\rule{0.2em}{0ex}}^{2}P$ series, weak Stark mixing from residual electric fields allowed observation of $n\phantom{\rule{0.2em}{0ex}}^{2}S$ and hydrogenic Stark manifold series at higher $n$. Limit analyses for the series yield the spectroscopic ionization energy ${E}_{I}(^{7}\mathrm{Li})=43\phantom{\rule{0.2em}{0ex}}487.159\phantom{\rule{0.2em}{0ex}}40(18)\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$. The $^{6,7}\mathrm{Li}$ isotope shift (IS) was measured in selected $n\phantom{\rule{0.2em}{0ex}}^{2}…
Stark broadening of hydrogen spectral lines with fine structure effects
2004
Formalism and numerical code have been elaborated for calculation of hydrogen line profiles in conditions of plasma in which Stark broadening and fine energy splitting are comparable and it is not possible to neglect either of them. It corresponds to the range of electron densities $10^{11} < N_e ({\rm cm}^{-3}) < 10^{15}$ . Lamb shift and spontaneous emission effects have also been included. Computer simulation method was applied in the calculations. Final results have been compared with experimental and theoretical findings by other authors.
Stark-Broadening Studies of N(I) Multiplet 3p 4P o–3d 4D at 1052.630 nm
2020
Stark-broadening studies of the N(I) multiplet 3p 4P o –3d 4D are reported. Our experimental electron impact widths of spectral lines are compared with the results of our calculations: (i) according to the standard impact theory of Griem with modification, (ii) using a computer simulation method which is based on numerical N-body code (CSM). Line shape measurements were performed using a wallstabilized arc. The radiation of the plasma emitted from homogenous plasma layers was measured using a grating spectrometer equipped with a two-dimensional detector.
Preparation of coherent superposition in a three-state system by adiabatic passage
2004
We examine the topology of eigenenergy surfaces associated to a three-state system driven by two quasi-resonant fields. We deduce mechanisms that allow us to generate various coherent superposition of two states using an additional field, far off resonances. We report the numerical validations in mercury atoms as a model system, creating the coherent superpositions of two excited states and of two states coupled by a Raman process.
Quasienergy states of trapped ions
2000
The quantum models for a single trapped ion are extended to the description of the collective dynamics for systems of ions confined in quadrupole electromagnetic traps with cylindrical symmetry. A class of quantum Hamiltonians with suitable axial and radial interaction potentials given by homogeneous functions of degree (-2) and invariant under translations and axial rotations are introduced. The considered axial and radial quantum Hamiltonians for the center-of-mass and relative motions are described by collective dynamical systems associated to the symplectic group \(\). Discrete quasienergy spectra are obtained and the corresponding quasienergy states are explicitly realized as \(\) cohe…
The Action Principles in Mechanics
2001
We begin this chapter with the definition of the action functional as time integral over the Lagrangian \(L(q_{i}(t),\dot{q}_{i}(t);t)\) of a dynamical system: $$\displaystyle{ S\left \{[q_{i}(t)];t_{1},t_{2}\right \} =\int _{ t_{1}}^{t_{2} }dt\,L(q_{i}(t),\dot{q}_{i}(t);t)\;. }$$
Exchange Interactions II: Spin Hamiltonians
1996
In Part I the physical mechanism of exchange interactions have been discussed. In this part we introduce the general concept of spin-hamiltonian. Isotropic exchange hamiltonian for many-electron polynuclear clusters (Heisenberg-Dirac-van Vleck-HDVV model [1-6]) will be derived. Spin-hamiltonian approach allows to separate the full exchange problem into two independent ones: 1) evaluation of the energy levels of the exchange system considering Jij as a set of semiempirical parameters, and 2) quantum mechanical calculation of exchange parameters with the aim of elucidation of the main physical mechanisms of the exchange coupling. In this part we shall focus on the problem of calculation of sp…