Violation of the optical bloch equations in power broadening of an impurity-ion solid,ruby

Power broadening (PB) of the optical holes for the transition (-1/2)⁴A₂?(-1/2)ē(²E) in ruby R₁ line was studied in the magnetic field (0.5 k0e) along the c-axis. It was found that the PB was much narrower than that expected from the optical Bloch equations. A qualitative interpretation based on a nonstochastic model is given.     

Modified optical bloch equations in nonlocal systems of two-level atoms interacting with ultrashort light pulses

Modified optical Bloch equations for two-level atoms in the radiation field with the complex polarization vector, the complex amplitude, and the complex wave vector are derived. A specific case is considered in which a field of this kind acts on a separate atom of a nonlocal atomic system. The solution of the modified equations for the interaction of atoms with ultrashort light pulses is obtained.     

Derivation of bloch equations from the time convolutionless generalized master equation

The generalized Bloch equations (GBE) describing the temporal evolution of a single two-level atom interacting with a classical external field of arbitrary intensity and with a thermodynamic bath are obtained from the time convolutionless generalized master equation or equivalently from the Tokuyama-Mori identity. These GBE are then used to calculate the absorption spectrum of a single two-level atom with frequency modulated by dichotomic noise with time-dependent transition probability.     

Transition from bloch equations to rate equations for multiple photon excitation of polyatomic molecules

A novel form of phenomenological optical Bloch equations, with density matrix elements depending both on the number of laser quanta in the pumped molecular vibrational mode and on the number of quanta dumped into the thermal bath formed by the remaining vibrational modes, is used to derive rate equations for multiple photon excitation of polyatomic molecules.     

New bloch period for interacting cold atoms in 1D optical lattices

This paper studies Bloch oscillations of ultracold atoms in an optical lattice, in the presence of atom-atom interactions. A new, interaction-induced Bloch period is identified. Analytical results are corroborated by realistic numerical calculations.     

Dynamical aspects of nucleus-nucleus collisions

This is an extension of the macroscopic theory of nucleus-nucleus reactions described by Swiatecki. The fusion or reseparation of two colliding nuclei is treated according to a schematic model based on the “chaotic regime dynamics” (liquid-drop potential energy plus one-body dissipation). Attention is focused on three hurdles or “milestone configurations” that a colliding system may be faced with: the touching configuration, the conditional saddle-point configuration at frozen mass asymmetry, and the unconditional saddle-point configuration. Semi-empirical formulae are derived for the “extra push” (the extra energy needed in some situations to carry the system from the first to the second hurdle) and for the “extra-extra push” (the energy needed to carry the system from the first to the third hurdle). The theoretical formulae are confronted with measurements of fusion and evaporation-residue cross sections. A discussion of the implications for super-heavy-element reactions is given, using the production of element 107 in the bombardment of ²⁰⁹Bi with ⁵⁴Cr as a calibrating reaction.     

Dynamical aspects of the adsorption hysteresis phenomenon

Equilibrium and nonequilibrium transport properties of adsorbates in mesoporous Vycor porous glass have been experimentally studied using nuclear magnetic resonance techniques. With the known geometrical characteristics of porous glass and with measured self-diffusivities, transient sorption curves have been quantitatively compared to those predicted within a Fick's law model. This model correctly describes data outside a hysteresis region. In contrast, in the hysteresis region, a two-step mechanism of density relaxation is required to explain the behavior. These two mechanisms are identified as diffusion at early stages and activated density redistribution at later stages of adsorption. The latter mechanism, being intrinsically slow in nature, is anticipated to prevent the system from reaching equilibrium.     

Dynamical oscillations in nonlinear optical media

The spatial dynamics of pulses in Kerr media with parabolic index profile are examined. It is found that when diffraction and graded-index have opposite signs propagating pulses exhibit an oscillatory pattern, similar to a breathing behavior. Furthermore, if the pulse and the index profile are not aligned the pulse oscillates around the index origin with frequency that depends on the values of the diffraction and index of refraction. These oscillations are not observed when diffraction and graded-index share the same sign.     

Dynamical aspects of fluctuations in linear conductors

A model is presented which describes the effect of a finite correlation length of the Peierls distortion on optical properties, width and position of the Raman line from the amplitude mode, and Knight shift in linear conductors. A canonical transformation to amplitude and phase variables is used which generalizes the linear transformation of Lee, Rice and Anderson. The non-linear effects are shown to be essential for the interpretation of experimental data in KCP.     

Dynamical aspects of intermediate-energy nucleus-nucleus collisions

Central collisions of heavy nuclei are investigated within the limit of selfconsistent independent single-particle motion in terms of the Wigner transform of the one-body density matrix in space and time. The energy regime considered extends from roughly 15 MeV/u to 150 MeV/u. Special attention is devoted to the relation between energy and momentum of the nucleons in the collision zone of the two nuclei. An initial average energy-momentum distributionf(k;E) is determined within the fully quantal approach which proves to be vital for our understanding of energetic particle production in the very early stage of the heavy-ion reaction. A comparison with related classical quantities shows the peculiar features of quantum dynamics for finite size fermion systems far from equilibrium.     

Dynamical aspects of intermediate-energy nucleus-nucleus collisions

The Uehling-Uhlenbeck collision term is derived from coupled equations of motion for the one-body density matrix and the two-body correlation function as obtained from the density-matrix hierarchy. The respective approximations introduced are related with energy and momentum conservation in single nucleon-nucleon collisions and found numerically to be approximately valid for energetic nucleon-nucleon collisions in case of intermediate energy heavy-ion reactions. Primary collision times of nucleons in the dinuclear reaction zone are calculated for various laboratory energies and the approach to local equilibrium is followed in time. Average relaxation times for highly excited finite nuclear systems are found to be considerably shorter than for related infinite nuclear matter problems, however, still too large as to allow for the formation of hot spots in nuclei.     

Dynamical aspects of precursor state kinetics

An examination of precursor adsorbed states from a dynamical viewpoint reveals that two commonly used models of precursor kinetics are not generally applicable. For the case of molecular chemisorption, simple, linear rate laws may not be valid unless the adsorbate-solid system meets certain dynamical criteria. On the other hand, for dissociatively chemisorbed species, a serious error can be made in estimating the effect of temperature on the adsorbate dissociation rate if one ignores, as is usually done, the temperature dependence of the initial sticking probability of the molecule.     

Dynamical aspects of the photoinduced phase transition in spin-crossover complexes

We report a dynamical study on the photoinduced cooperative changes of the spin configurations in single crystals of the organometal spin-crossover complex. In the photoswitching process between low- and high-spin states, nonlinear characteristics such as thresholdlike behavior, incubation period, and phase separation have been observed. These results demonstrate that the cooperative intersystem crossing mediated by spin-lattice interaction plays a key role in the driving process of a new class of nonequilibrium phenomena so called photoinduced phase transition.     

A circular system of coupled waveguides and an optical analogue of bloch oscillations

The process of light propagation in a nonuniform system of tunnel-coupled waveguides is studied. The nonuniform system of waveguides is realized by making a circular system of waveguides on the inner wall of a supporting tube with the help of the SPCVD technology, which is designed for the synthesis of preforms of optical fibers. It is shown that the waveguide light beam propagates in such a system along a wavelike trajectory and partially radiates outwards at the crests of this trajectory. The oscillation period of the trajectory is measured, and it is shown that it is possible to input radiation into the waveguide mode by the process that is inverse to the process of light emission from the structure.     

Dynamical coupling in the differential equations approach to atom-diatom exchange reactions

The atomic exchange reaction A + BC → AB + C is investigated quantum mechanically employing a coupled differential equations approach. The relative motion in reactant and product channels is described in the common coordinate R ₃ (the AC nuclear separation) and is developed in three-dimensional space. The total wave functions of the system are expressed as a superposition of valence bond electronic states of the initial (A, BC) and final (AB, C) configurations, with the coefficients describing the relative and internal (vibrational, rotational) nuclear motions. Choosing convenient trial functions with the appropriate boundary conditions and using the Kohn variational principle, a set of differential (rather than the usual integro-differential) equations is obtained for the relative motion wave functions in R ₃. The potential matrix elements turn out to be dynamical in that they depend on the initial k ₁ and final k ₂ wave vectors. Two-state coupled channel calculations of the differential and integral cross sections for the isotopic species D + H₂, H + H₂ and D + D₂ are presented for collision energies up to 0·8 eV.     

Dynamical aspects of large angle heavy-ion scattering

The recent data on large-angle scattering of heavy ions are reviewed. Typical features of these data are anomalously large cross sections in the backward hemisphere, strongly oscillatory angular distributions, and highly regular gross structures modulated by much narrower structures in excitation functions. A critical evaluation is presented of the different models proposed to understand various aspects of the data. Independent of these models, all the data show that the nuclear surface is more transparent than previously thought. The presence in the excitation functions of both narrow and broad structures indicates that there is an interplay of various reaction times, ranging from the lifetime of the compound nucleus to the time associated with shape resonances in the ion-ion potentials. Partly because of this apparently very complex reaction mechanism, there is at present no quantitative all-encompassing understanding of the physical origin of the observed phenomena. Promising avenues for future theoretical and experimental investigations are pointed out.     

On the bloch wall motion in multilayer films

A Bloch wall is considered which is pinned along its intersection line with the film surface and bent due to the action of an external field. It can be shown that beyond a critical field the wall starts to move irreversibly. In film systems consisting of hard and soft films the pinning may be caused by the connection between the walls in the different films. In this case the calculation of the critical field gives a value which is the flux-weighted average of the coercive fields of the hard and soft films in agreement with previous experimental results of Crowther.     

Dynamical equations of quantum information and Gaussian channel

A subdynamic based kinetic equation (SKE) for quantum information density (QID) is presented and using this is shown that the Liouville equation, Master equation and Fokker–Planck equation for QID all share the same formalism as the density operator. This allows one to directly use QID for studying quantum communication and to construct a quantum Gaussian channel. The channel is described by a quantum Fokker–Planck equation, which permits harmonic oscillator encoded information to transmit quantum signals with quantum parallelism. The quantum dynamical mutual information for this channel is also calculated.