We describe the coherence properties of light emitted by driven atoms in terms of dressed-atom survival amplitudes. Such amplitudes can be used to construct analytic expressions for the function describing the delay between successive photon emissions and used to construct the appropriate radiation correlation functions. This approach is used to calculate the radiative dynamics of three-level atoms appropriate to recent quantum-jump experiments. We contrast our simple approach to that normally employed which relies on the numerical solutions of density-matrix equations of motion followed by the application of the quantum-regression theorem.

The behavior of the dipole moment of a three-level atom interacting with cavity fields of arbitrary detunings is investigated. The time evolution and squeezing conditions of the components and correlation function of the dipole moment are calculated for three cases: one-mode field and a Ξ-type atom initially in the upper state, two-mode field and a Λ-type atom initially in the upper state, and two-mode field and a Λ-type atom initially in one of the lower states. A number of interesting features are found and discussed.

A quantum theory of a two-level single-mode laser with injected atomic coherence is developed by generalizing the Scully-Lamb laser theory to a form appropriate for the analysis of a coherently pumped laser. We assume that the active atoms are prepared initially in a coherent superposition of the upper and lower levels, and we derive the master equation for the field density operator by treating the interaction of the laser field with many active atoms simultaneously. It is shown that the photon-number distribution can be exactly Poissonian. The laser operation is analyzed in terms of the Fokker-Planck equation for the laser field. Both the intensity and phase diffusion coefficients are phase sensitive and, for stable laser operation, become much smaller than those of an ordinary laser. Consequently, the injected atomic coherence reduces both the photon-number noise and phase noise simultaneously. The intensity diffusion coefficient can vanish exactly, and at the same time the phase diffusion coefficient can become very small. This leads to spontaneous-emission noise quenching in the photon-number distribution, and the laser field can become very close to a coherent state. A scheme to generate the proper form of the initial atomic coherence necessary for the quantum noise quenching is proposed and analyzed.

We study the steady-state operation and noise properties of a laser (or maser) exhibiting phase locking when an ordinary vacuum is replaced by a squeezed vacuum. Such a phase-sensitive laser can be realized by preparing the active medium initially in a coherent superposition of levels involved in the laser transition. We develop a general formalism to treat number-phase fluctuations and quadrature fluctuations. When applied to a one-photon laser with injected atomic coherence, we find that not only is a complete quenching of the (spontaneous-emission) quantum noise possible, but the field can actually be in a squeezed state. The variance in either amplitude or phase quadrature can be below the vacuum noise level by a factor of 2 (50%) at the expense of enhanced fluctuations in the other quadrature.

We make a comparative study of various quasiprobability distributions in phase-sensitive quantum-optical systems. Starting from a general, linear master equation for the field, which emerges in different models of correlated-emission lasers, we derive the Fokker-Planck equations in the Glauber-Sudarshan P, the antinormal ordering Q, the Wigner W, the complex P, and the positive P representations and find the steady-state solutions for the five distributions. Simple relations between the complex and positive P functions are discovered for the first time. Various moments calculated by using these distributions are found to be identical, as expected. An application of these distributions to the two-photon correlated-emission laser shows that the intracavity field can be near-perfectly squeezed in the phase quadrature and the maximum quadrature squeezing is reached when the mean laser amplitude vanishes.

We present a general formalism for the description of gas-kinetic effects of light in a single-component gas, by elimination of rapid variables in the evolution equations. These equations contain both Boltzmann terms describing velocity-changing collisions and radiative transitions. The general result is a set of generalized Navier-Stokes equations for the density, the temperature, and the hydrodynamic velocity. The effects of the incident radiation on the transport properties of the gas are illustrated by deriving explicit transport equations in a simple model case. This shows that both the intensity and the intensity gradient serve as a thermodynamic force.

Since experimentally feasible configurations of laser-assisted Thomson scattering are quasiclassical, and since semiclassical calculations tend to be lengthy and—in view of the numerous approximations required—lead to results that are difficult to assess, it is demonstrated that the corresponding classical cross section can be derived not only much more simply but also essentially exactly. This cross section, valid for arbitrary intensities of the ‘‘assisting’’ laser field and for arbitrary electron-injection energies, is then graphically compared with semiclassical results from the literature. It shows a published nonrelativistic result to be essentially correct, but its relativistic generalization to be incorrect. As for sum rules, which in the semiclassical literature have only been obtained by recourse to drastic approximations, it is shown that the classical approach straightforwardly yields exact cross sections for the overall laser-assisted Thomson scattering, which again are valid for arbitrary laser intensities and arbitrary electron-injection energies.

The generalized exchange local-spin-density-functional theory with self-interaction correction and correction of the statistical exchange potential was used to calculate the electron affinities of alkaline-earth and actinide elements. The effect of relativistic correction by the mass velocity and Darwin terms and correlation correction on the electron affinities is discussed. The calculation of the negative ions shows that, although the correlation correction to the potential is very small, it is essential for obtaining converged values for most of the negative ions. The calculated results predict stable negative ions for the alkaline-earth elements Ca, Sr, Ba, and Ra, supporting the calculations of Vosko et al. [Phys. Rev. A 39, 446 (1989)] and Fischer [Phys. Rev. Lett. 59, 2263 (1987); Phys. Rev. A 39, 963 (1989)]. Estimated electron affinities for the actinide elements are given.

We study the influence of noise on the delay experienced by a steady bifurcation point involving a zero or constant solution when the control parameter is swept in time starting in the vicinity of the stable constant solution. This study is realized by a direct analysis of the moment equations rather than via a Fokker-Planck equation with an emphasis on analytical results. We treat separately multiplicative and additive noise sources and the noise can be white or colored. Furthermore, we analyze the case where the noise is added during the sweep but is absent during the preparation of the system and compare it with the case where noise is already present during the preparation of the system. In general, noise reduces the delay even to the extent that the bifurcation point can occur before the static bifurcation point. However, when the initial condition is noisy the delay may increase beyond the deterministic value in the limit of strongly colored noise.

We have measured variations of Saffman-Taylor flows by changing dimensionless surface tension B alone and by changing B in conjunction with changes in dimensionless viscosity contrast A. Our low-aspect-ratio cell permits close study of the linear- and early nonlinear-flow regimes. Our critical binary-liquid sample allows study of very low values of A. The predictions of linear stability analysis work well for predicting which length scales are important, but discrepancies are observed for growth rates. We observe an empirical scaling law for growth of the Fourier modes of the patterns in the linear regime. The observed front propagation velocity for side-wall disturbances is constantly 2±1 in dimensionless units, a value consistent with the predictions of Langer and of van Saarloos. Patterns in both the linear and nonlinear regimes collapse impressively under the scaling suggested by the Hele-Shaw equations. Violations of scaling due to wetting phenomena are not evident here, presumably because the wetting properties of the two phases of the critical binary liquid are so similar; thus direct comparison with large-scale Hele-Shaw simulations should be meaningful.

An external field coupled with the two-body density distribution function leads to a generalization of the density-functional theory in which the free energy is regarded as a functional not only of the density but also of the two-body distribution function. The generalized formalism is applied to the liquid-structure theory in the presence of a weak three-body potential. In the first-order calculation, the three-body effects are fully taken into account through modification of the pair potential; the structure of the pair-potential theory remains intact. Such a renormalizability, which was proven diagrammatically, is ascribed to the variational property of the free-energy functional. An approximate expression for the nonadditive correction which is amenable to the numerical computations is obtained within the hypernetted-chain theory.

The effect of Coulomb screening on the inverse bremsstrahlung heating process in a plasma illuminated by two laser fields is discussed. It is shown that, although the screening effect actually lowers the Coulomb interaction, one might accomplish a reduction of the weakening effect and consequently an enhancement of the collisional plasma heating, by illuminating the plasma with the two electromagnetic waves having a difference in frequency close to the plasma frequency.

It is shown that a scheme of beam-beam collisions which makes a head-on collision in a transversely boosted frame is applicable to storage-ring colliders. This scheme allows a large crossing angle at the collision point without an excitation of synchrotron-betatron resonances, and will give merits in designing high-luminosity colliders.

Discontinuous (first-order) anchoring transitions are shown to occur as a function of water adsorption at the nematic-liquid-crystal(E9)–gypsum and E9-mica interfaces. The transitions involve growth of domains with an anchoring a’ making a finite angle with the direction a of the parent anchoring. The growth proceeds by motion of walls separating the domains with the new anchoring a’ from the matrix with the parental anchoring a. A Landau-type expression for the interfacial energy is proposed and used to classify the anchoring transitions and to explain the behavior of the domains during the first-order anchoring transitions.

We study pair correlations in a plasma of two repulsive components at different temperatures and a neutralizing background. The validity of the polarization approximation and the hypernetted-chain approximation is examined by comparing with computer simulations for weak and strong coupling, respectively. We find that a separation of space and momentum correlations is favored if the coupling between the components takes place at low frequencies or if the frequent collisions at high densities suppress the dynamical polarization.

The novel technique of point-projection backlighting is used to probe a laser-produced plasma. A spatially restricted source of x rays is created by irradiating a fiber which is used to backlight a plasma. Temporal resolution of the absorption spectrum is obtained by creating the backlight with a pulse that is delayed in time from the main, plasma-producing, laser. The backlight can also be of shorter duration than the main laser pulse providing for enhanced time resolution and therefore less temporal averaging. The results for low-Z aluminum and silicon targets are presented. The low-Z absorption spectra using both low-Z (e.g., aluminum) and high-Z (e.g., molybdenum) elements for backlighting are studied. A description of this technique and the analysis of the data obtained is presented.

By means of the two-fluid model of Braginskii [Reviews of Plasma Physics, edited by M. A. Leontovich (Consultants Bureau, New York, 1965), Vol. I, p. 205], this paper derives a set of nonlinear differential equations governing the dynamics of fully toroidal low-frequency electromagnetic waves in an inhomogeneous electron-ion plasma immersed in a nonuniform magnetic field. The effects of equilibrium electron and ion pressure gradients, magnetic drifts caused by the nonuniform magnetic field, as well as the contribution of heat fluxes in the particle-energy transport equations are incorporated. In the linear limit, expressions for the ion and electron number-density perturbations together with a new dispersion relation for fully toroidal electromagnetic waves are obtained. A new long-wavelength electromagnetic drift wave instability is shown to exist in a nonuniform magne- tized electron plasma. The formation of dipolar vortices in the two-dimensional ion-temperature-gradient-driven electrostatic drift wave turbulence has been demonstrated.

Extended thermodynamics of heat-conducting fluids is used to give explicit formulas for non- equilibrium energy density of ideal gas expressed as functions of classical variables and the diffusive entropy flux (a nonequilibrium variable). A Lagrangian density associated with the energy density is used to obtain the components of energy-momentum tensor and corresponding conservation laws on the basis of Hamilton’s principle of stationary action and Noether’s theorem. The heat flux appears naturally as a consequence of a free entropy transfer (independent of mass transfer) and a momentum transport is associated with tangential stresses resulting from this entropy transfer. The compatibility of the present description with the kinetic theory is shown. Hamilton’s principle is extended so that the flux of entropy as well as the fluxes and densities of mass are varied independently. The concept of thermal momentum as the derivative of the kinetic potential with respect to the entropy flux is introduced; this quality plays a fundamental role in the extension of Gibbs’s equation to describe a nonequilibrium fluid with heat flux.

Starting from any two finite expectation values, rigorous bounds to quantities of D-dimensional many-particle systems, depending on the single-particle density ρ(r) in the form F${\rho }^n$$d^D$r, n∈${\mathrm{openR}}^{+}$ (the set of positive real numbers), are explicitly given. Similar bounds are also valid in momentum space. The resulting expressions are used to rigorously bound the kinetic ($T_0$,D) and Dirac exchange ($K_0$,D) energies of fermionic systems in the plane-wave approximation (e.g., the Thomas-Fermi approach). As a numerical illustration, very accurate upper bounds to the Dirac exchange energy of atomic systems are found by means of 〈$r^{\mathrm{-}1}$〉 and 〈$r^{\mathrm{-}2}$〉. The limit of large dimensionality is also considered; in particular, it is found that $T_0$,D≥${\mathrm{D}}^2$〈${\mathrm{r}}^{\mathrm{-}2}$〉/2${\mathrm{e}}^2$ and $K_0$,D≤-2〈${\mathrm{r}}^{\mathrm{-}1}$〉/πe, where e=2.718 28. In addition rigorous lower bounds to the exact kinetic energy of real (D=3) fermionic systems are given.

In this paper a laser Doppler velocimetry (LDV) experiment with a water flow is performed to show that the experimental results for the Fourier transform of the two-photon time-interval probability $Q_F$(ν) agree with the theoretical results derived in previous papers. The conclusions of these papers can therefore be applied to a real LDV experiment. It is concluded that by using this technique for small scattered intensities the velocities can be obtained with much more accuracy than by measuring the autocorrelation function $g^{\mathrm{}\left(2\right)\mathrm{}}$(τ). The values of the intensity and of the Doppler frequencies that can be used are discussed.