The Jaynes-Cummings model of a two-level atom interacting with a single-mode radiation field is examined when the radiation is initially in a squeezed state with varying degrees of squeezing. The dynamical response is studied resorting to an exact integral representation valid for all mean photon numbers of the field, and using the saddle-point method to estimate the integral. Our results confirm and extend the predictions deduced from previous numerical studies.

We have shown that an energylike integral of motion for semiclassical Maxwell-Bloch equations that describe the dynamics of N identical two-level atoms interacting with a single-mode, self-consistent, classical electromagnetic field can be recast into the form of an autonomous Hamiltonian for a system with two degrees of freedom. A stochasticity criterion has been derived using Chirikov’s method of resonance overlap.

The mirrors of an interferometer may be rendered dynamically unstable by the radiation pressure of the sensing light. We assess the importance of this effect for optical cavities, concentrating in particular on proposed laser-interferometric gravitational wave detectors. Both broadband and narrow-band systems are considered. While the potential instabilities may well be important for cavities with weak suspensions, realistic gravitational wave detectors should not encounter any problems.

For many years there have been two expressions for the natural radiative line shape, depending on the form of the Hamiltonian assumed for the interaction of an atom with the radiation field. It is shown that this difference arises from artificial assumptions about the atom-field interaction, and that the same line shape is obtained from either form under the appropriate physical assumptions.

We study the radiative dynamics of a single charged particle in the fields of an oblique, rotating magnetic dipole and an attractive charge. We numerically find that there exists a class of solutions corresponding to bounded orbits at a distance greater than c/Ω, where Ω is the angular velocity of the magnetic dipole. In an independent-particle picture, particles started with different initial conditions within the basin of attraction of this class of orbits will eventually establish such a phase relationship with one another as to form a ring of particles around the rotational axis of the dipole. We also show the existence of phase-locked dynamics for this system. These results suggest a possible structure of the outer magnetosphere of a nonaligned pulsar.

By making use of nonlinear simulation, this paper investigates the influences of the initial parameters on the efficiency in a large-orbit nonwiggler free-electron laser (cyclotron-autoresonance-maser-like). It is found that the cyclotron-autoresonance condition does not prevail in the large-orbit regime. Simulation shows that this device may have quite attractive features compared to other sources of millimeter and submillimeter waves.

The laser with saturable absorber (LSA) with level structures in amplifier and absorber media has been modeled in a rate-equation approach introducing memory functions. This approach has been applied to vibrational structures in a ${\mathrm{CO}}_2$ medium and rotovibrational structures in molecular absorbers. Experimental results for the LSA regimes with inhomogeneously and homogeneously broadened absorbers are presented. The theoretical results for the laser threshold and the Hopf bifurcation are derived by the model through a fitting of the laser-absorber coupling parameters.

The inhibition of atomic phase decays by squeezed light, as first predicted by Gardiner [Phys. Rev. Lett. 56, 1917 (1986)], has yet to be confirmed experimentally. A major obstacle to such an experiment is the production of an effective squeezed-vacuum–atom coupling, so that the atom interacts only with squeezed modes of the radiation field. In this paper we propose the use of a microscopic plane-mirror Fabry-Pérot cavity to effect a strong selection of modes coupling to the atom. It is shown that a significant reduction in fluctuations experienced by the atom can be achieved in one quadrature, with an input squeezed beam of modest angular dimensions, provided that the phase (and to lesser extent the amplitude) characteristics of the input beam are suitably matched to the cavity.

We formulate a general description of the inelastic interaction between charged particles and a degenerate plasma in the presence of a strong laser field. The excitations in the plasma are described according to the random-phase-approximation formalism, in terms of the dielectric function of the medium, and including the effects of the laser field on the dynamical response. The energy exchange and the scattering rate of the particle in the plasma are modified by multiphoton processes. The formalism describes the excitation of plasmons and electron-hole pairs, with simultaneous emission or absorption of photons. We calculate the contribution of these processes to the energy-loss rate and to the mean free path of the particle in the range of solid-state densities. New effects due to the laser field are expected for intensities similar to those used in laser fusion experiments.

We develop and test a direct method for computing two-particle excess entropies in the canonical ensemble. The method is based on a systematic expansion of the entropy into one-body, two-body, three-body, etc., contributions. Unlike earlier canonical ensemble methods the resulting expressions for the entropy are local. It is shown that, at liquid densities, the three-body (and higher) terms are small but not negligible. The largest discrepancies are found at intermediate densities.

Following a brief review of the analytic solution for the relativistic motion of a single electron in a pulse of very strong plane-wave radiation, numerical simulations are presented that probe the effects of space-charge forces and spatial inhomogeneity of the radiation upon the one-electron dynamics. The nonlinearities introduced by relativistic effects can lead to irregular dynamics. For pulses with a smoothly varying temporal envelope the behavior of electrons that are ionized during the pulse can be very different from that of ambient electrons. The calculations support the use of short-pulsed lasers to produce high-energy electrons and incoherent x rays, but reveal possible difficulties in the formation of cold overionized plasmas suitable for recombination lasers.

The formation of a distribution of various size droplets is a characteristic feature of many systems from thin films and breath figures to fog and clouds. In this paper we present the results of our investigations of the kinetics of droplet growth and coalescence. In general, droplet formation occurs either by spontaneous nucleation or by growth from heterogeneously distributed nucleation centers, such as impurities. We have introduced two models to describe these two types of processes. In the homogeneous nucleation model droplets can form and grow anywhere in the system. The results of the simulations of the model are presented and it is shown that the droplet size distribution has a bimodal structure consisting of a monodispersed distribution of large droplets superimposed on a polydispersed distribution of smaller droplets. A scaling description for the evolution of the time-dependent droplet size distribution and its moments is presented and it is found that the scaling predictions are in excellent agreement with the simulations. A rate-equation similar to the Smoluchowski equation is also introduced for describing the kinetics of homogeneous droplet growth. The results of the simulations of the homogeneous nucleation model are also compared with the experiments on droplet growth in thin films obtained by vapor deposition of tin on sapphire substrate. It appears that this model captures the essential features of the distribution of droplets in the vapor deposition experiments. We also introduce a heterogeneous nucleation model for studying processes in which droplets only form and grow at certain nucleation centers which are initially chosen at random. Simulations, scaling theory, and a kinetic equation approach for describing the heterogeneously nucleated droplet growth model are also presented. The theoretical predictions are found to be in excellent agreement with the simulations.

The five-moment method in gaseous electronics is based on a model velocity distribution function with position-dependent parameters, such as density (one moment), average velocity (three moments), and average energy (one moment). Temporal and spatial dependence of these parameters is determined by solution of velocity moments of the Boltzmann equation, which are coupled, partial differential equations in time and space. In this paper velocity moments of the Boltzmann equation, including moments of the collision integral for elastic and inelastic collisions, are given for two model distribution functions—shifted Maxwellian and shifted shell—and solved for the case of a planar Townsend discharge in helium, including nonequilibrium regions near electrodes. Based on a comparison between calculated and measured values of α/N versus E/N, it is concluded that five-moment theory based on a shifted Maxwellian distribution is superior to either the five-moment theory based on a shifted shell distribution, or the two-moment theory based on a monoenergetic beam distribution.

The dynamical evolution away from an unstable steady state is studied for the two-sided symmetric model in two dimensions by means of numerically solving the interface equations of motion. Evidence is presented for the appearance of a regime of self-similar growth in which the pattern is characterized by a single length scale R(t). The asymptotic time dependence of such a length is R(t)∼t. The results also show that the local deviation of the interface from planarity, the local normal growth velocity, and the power spectrum of the interface satisfy scaling relations. In addition, by assuming the existence of such a scaling regime, we are able to derive from dimensional and heuristic arguments a power-law growth with exponents in accord with those found in the numerical solution.

We report measured Stark widths and shifts of the neutral helium lines 3889 and 5876 Å in hydrogen-helium, pure helium, and argon-helium plasmas. A pulsed low-pressure arc is used as a plasma source. Electron densities of (2–10)×${10}^{16}$ ${\mathrm{cm}}^{\mathrm{-}3}$ are measured by laser interferometry, electron temperatures in the range from 31 000 to 42 000 K are determined from the intensity ratio of O ii impurity lines, and the gas temperature is determined from the Doppler component of the O ii line profile. Experimental Stark widths and shifts are compared with theoretical results obtained from three sets of semiclassical calculations of Stark-broadening parameters using quasistatic and ion-dynamic treatment of the ions. Inclusion of ion dynamics in the calculation of widths and shifts considerably improves the agreement between theory and experiments. The results of the comparison show a constant systematic discrepancy between three semiclassical calculations and the experiment. These results suggest the possibility of plasma-electron-density diagnostics with a precision in the range 3–5 %.

In this paper we determine the contributions to the Rayleigh line for a noncritical binary liquid mixture in a temperature gradient using the technique of fluctuating hydrodynamics in a uniform-pressure approximation. The steady-state temperature gradient induces a steady-state concentration gradient in the liquid mixture. We predict a large enhancement to the Rayleigh line from concentration fluctuations that depends upon the square of the concentration gradient. The occurrence of two gradients within the liquid also gives rise to additional cross-coupling gradient contributions.

In a multiple-keV-temperature deuterium plasma such as that in the Joint European Torus (JET), C vi emission arises from excitation processes that, in the absence of neutral-hydrogen-beam heating, occur near the plasma boundary. Distortion to the C vi Lyman decrement, such as the Ly-β:Ly-γ:Ly-δ ratio, and enhancement of high series members (around 1s-12p) are observed. In this situation, large influxes of ${\mathrm{D}}^0$ atoms are anticipated at the plasma boundary when the plasma is limited by the carbon inner wall. The intensities of the Lyman-series members are interpreted in terms of electronic excitation of ${\mathrm{C}}^{5+}$ ions in their ground state as well as charge-exchange collisions between ${\mathrm{C}}^{6+}$ ions and thermal ${\mathrm{D}}^0$ atoms, either in their ground state or in their excited states (up to the collision limit). The line-of-sight emission is modeled using an impurity-ion transport code requiring knowledge of the electron temperature, electron density, and ${\mathrm{D}}^0$ radial profiles. Comparison of the observed relative intensities of the C vi Lyman series Ly-β, Ly-γ, Ly-δ, etc., with the model calculations allows plausible corrections to be made to the effective charge-exchange rate coefficients as a function of the principal quantum number. The observations offer a potential method of measuring local ${\mathrm{D}}^0$ concentrations near the boundary in high-temperature, high-${\mathrm{D}}^0$-concentration recycling plasmas.

Hamiltonian or variational formulations of the Maxwell-Vlasov equation naturally yield expressions for the free energy available upon perturbation of an equilibrium. The noncanonical Hamiltonian, Hamilton-Jacobi, and Lagrangian formulations are used to obtain such expressions. It is concluded that all interesting equilibria are either linearly unstable or possess negative-energy modes.

A FTHETA-pinch light source has been used to observe the spectrum of krypton ionized four times (Kr v) in the vacuum-ultraviolet region (432–2000 Å), and 50 lines have been identified as combinations between levels of the 4$s^2$4$p^2$, 4s4$p^3$, and 4$s^2$4p4d configurations. For 19 of the lines the classification is new. All but four of the 27 levels that belong to the configurations have been determined. The energy parameters were obtained using Hartree-Fock calculations. The configurations are interpreted by fitting the theoretical energy expressions to the observed levels using least-squares techniques. Isoelectronic comparisons along the Ge i isoelectronic sequence have been used to support the experimental results.

A theory of the magnetic field diffusion is developed in order to explain high-energy x-ray emission observed in vacuum spark plasmas. The acceleration mechanism is based on the intense induced electric field due to an abrupt inductance change when the plasma column expands from its pinch radius to a large radius. According to this magnetic field diffusion model, high-energy electrons are well collimated at the axis. In addition, the electron energy in this collimated flux can be easily more than 20 times the electrode voltage, which generates high-energy x-ray radiation by interaction with the dense plasma.