High-resolution photoabsorption spectra of copper and silver are reported in the d-subshell excitation region that reveal well-resolved level structure for the 3${\mathit{d}}^9$4s6p, 3${\mathit{d}}^9$4s4f, 4${\mathit{d}}^9$5s7p, and 4${\mathit{d}}^9$5s4f configurations. A consistent set of level assignments is suggested within the framework of the ${\mathit{J}}_{\mathit{c}}$K coupling scheme. The fine-structure splittings in the 4f excited levels are reported.

The near-K-edge x-ray photoabsorption spectrum of xenon was measured using synchrotron radiation. Several simultaneous two-electron excitation features were detected. Their identification is supported by nonrelativistic and relativistic energy-level calculations. The relative cross sections extracted from the data are consistent with previous measurements on Kr. Relativistic sudden-approximation-shake-theory cross sections are found to overestimate the measured ones by factors of 2–3, but closely follow level-dependent trends in the measured data.

In a recently published perturbation theory study of multiphoton-ionization cross sections of ${\mathrm{H}}^{\mathrm{-}}$ [S. Geltman, Phys. Rev. A 43, 4930 (1991)], a serious discrepancy was reported between the model-based results and previous ab initio Floquet-theorem-based coordinate rotation results [M. Crance, J. Phys. B 23, L285 (1990)]. We present two-and three-photon ionization cross sections from many-electron, many-photon-theory nonperturbative calculations, which essentially agree with Geltman’s results. This finding supports our earlier conclusions on the physics of photodetachment without or with an external static field.

We study the resonant interaction of a two-level atom with one mode of the electromagnetic field. We calculate the entropy associated with the atomic state evolving from arbitrary initial conditions. We show that pure atomic states can be generated from an arbitrary initial mixed atomic state. Also, we observe and discuss a significant difference in the long-time behavior of the entropy for an initial number state and a coherent state.

Fluctuations of the square of the field amplitude inside and outside a degenerate parametric oscillator are investigated. It is shown that a large reduction of the noise of the square of the field amplitude can be achieved outside the cavity while the maximum amplitude-squared squeezing inside the cavity is only by 50%. This situation is similar to that for normal squeezing.

Some of the general properties of the power spectrum are presented, and sum rules for spectrum analysis stated.

We use generalized dimensions to compare the dynamics of an optically pumped ${\mathrm{NH}}_3$ ring laser with that of the Lorenz model. While for pure single-mode emission we find excellent agreement between dimension spectra of the laser and the Lorenz attractor, for conditions of existence of a second counterpropagating mode, dimensions are found to be higher. Thus the dimension spectra reflect the larger phase space occupied by the attractor. As a further result of that comparison, we find that the frequently used correlation dimension ${\mathit{D}}_2$ as an estimate for the Hausdorff dimension ${\mathit{D}}_0$ can differ substantially from ${\mathit{D}}_0$, and shows little sensitivity to attractor changes.

We have studied the phase properties of coherent light in the M-photon Jaynes-Cummings model using the Hermitian phase operator of Pegg and Barnett [Europhys. Lett. 6, 483 (1988)] and have found the collapse and revival phenomenon about the long-time behavior of the phase variance of the field. Also, we have given a reasonable interpretation of the phenomenon.

In a recent paper Martin et al. [Phys. Rev. A 42, 6570 (1990)] report on wavelength measurements in two- and three-electron krypton ions. Their results for the 1${\mathit{s}}^2$2s ${}_{}{}^2{}_{}{}^{}$${\mathit{S}}_{1/2–}$1${\mathit{s}}^2$2p ${}_{}{}^2{}_{}{}^{}$${\mathit{P}}_{1/2,3/2}$ transitions in lithiumlike Kr xxxiv are in disagreement with our previous measurements [B. Denne, E. Hinnov, J. Ramette, and B. Saoutic, Phys. Rev. A 40, 1488 (1989)]. Martin et al. suggest that this difference could be due to Doppler shifts affecting our measurements. In this Comment we disprove this explanation and further show that there is a discrepancy between the beam-foil measurements of Martin et al. for Kr and Xe and the isoelectronic trend established from tokamak measurements of the 2s-2p transition wavelengths in the lithium sequence.

Reiss [Phys. Rev. A 42, 1476 (1990)] has argued that Volkov states exist unambiguously only in relativistic theory, and that ${\mathbf{A}}^2$ must be retained in strong-field theory even after the nonrelativistic and dipole approximations are made. We show that these arguments and their conclusions are incorrect.

Milonni [preceding Comment, Phys. Rev. A 45, 2138 (1992)] raises objections to my work [Phys. Rev. A 42, 1476 (1990)] on Keldysh-like methods in photoionization. His results are shown to follow from procedures that are inappropriate to the strong-field environment of the Keldysh method. These procedures lead to physical inconsistencies. My technique is verified to be rigorous and unique.

We show that for a subfamily of Hénon maps, all having the same Jacobian determinant J, the largest Lyapunov exponent has a minimum negative value ${\lambda }_{\mathit{L},\mathrm{m}\mathrm{i}\mathrm{n}}$=lnJ/2, which occurs when a periodic orbit of any period N is the attractor, and the linear eigenvalues at any period N stable fixed point are complex. We discuss the sizes of the parameter regions in which this effect occurs.

We model the self-organizing dynamics of two-dimensional magnetic-domain patterns. Using a random-neighbor approximation, avalanches of topological rearrangements and domain destruction are easily simulated numerically, and asymptotic forms for distributions of avalanche sizes and lifetimes can be given analytically. Recent experimental results for such distributions are found to obey these asymptotic forms, which permits us to classify the self-organized state observed in experiments as subcritical.

We begin the development of a thermodynamic and stochastic theory of electrical circuits approaching nonequilibrium stationary states containing linear or nonlinear capacitors, resistors, and inductors. We restrict ourselves to circuits with only point attractors. The theory centers around a function φ, and we show that: (1) it is the macroscopic driving force to a stationary state, (2) it is a global Liapunov function, (3) it provides necessary and sufficient conditions for the existence and stability of stationary states, (4) its time derivative is a component of the total dissipation, (5) it is an excess work of moving the circuit away from the stationary state, and (6) it determines a stationary probability distribution of a Fokker-Planck equation. The generalization from linear to nonlinear circuits is made with the concept of an instantaneous mapping from the nonlinear circuit to a thermodynamically and kinetically equivalent linear circuit. A translation of chemical to electrical networks holds at the thermodynamic but not stochastic level of description.

The evolutionary history of elastic materials subjected to the shear stress and the high confining pressures encountered in seismological applications is simulated by a set of avalanche models. Some models exhibit bimodal fracture-size distributions reminiscent of a first-order phase transition, while others have scaling behavior. We argue that this scaling behavior arises as a consequence of the high degree of self-generated roughness. In all models the scaling region broadens as surface roughness is increased. An epidemic growth model, closely related to the avalanche models, is introduced to understand the statistical properties obtained in the simulations. By means of these alternative formulations we interpret the scaling in the size distributions of the avalanche models as a finite-size effect; the system self-organizes, tuning itself to a size-dependent steady state which exhibits an apparent criticality. A value for the scaling exponent, determined from the epidemic model by way of correlated percolation theory, is in good agreement with the numerical result. These problems have relevance to sandpile and earthquake models and to aspects of self-organized criticality.

Several problems in the theory of photon migration in a turbid medium suggest the utility of calculating solutions of the telegrapher’s equation in the presence of traps. This paper contains two such solutions for the one-dimensional problem, the first being for a semi-infinite line terminated by a trap, and the second being for a finite line terminated by two traps. Because solutions to the telegrapher’s equation represent an interpolation between wavelike and diffusive phenomena, they will exhibit discontinuities even in the presence of traps.

The effects of correlations in deposition processes of sandpile-avalanche models are investigated numerically. Simulations are carried out for two models, a weight model and a minimum model. It becomes evident that in the presence of correlations, critical exponents associated with lifetime and avalanche-size distributions vary continuously with changing a parameter, and universality does not hold. The breakdown of power-law behavior and self-organized criticality due to strong correlations is also demonstrated.

It has recently been shown by Evans, Cohen, and Morriss [Phys. Rev. A 42, 5990 (1990)] that bulk thermal-transport coefficients can be calculated from the maximal Lyapunov exponents by using the conjugate-pairing rule. In the present paper we use computer simulation to explore the validity of the rule under conditions which are more general than those used in the derivation by Evans, Cohen, and Morriss. We show that the existence of a IsteadyP state for dissipative dynamics and the satisfaction of the condition known as the adiabatic incompressibility of phase space (i.e., area preserving in the absence of a thermostat) are insufficient for the rule to hold. We also show that the linear field-induced shift of the Lyapunov exponents with respect to the exponent index, is among the nonequilibrium molecular-dynamics algorithms, apparently peculiar to the SLLOD algorithm (so named because of its close relationship to the Dolls tensor algorithm) for shear flow.

The physics of an ensemble of oscillating two-state particles and antiparticles, interacting elastically and inelastically with a heat bath and particle reservoir, is examined. In particular, the effect that the interactions have on the quantum coherence, or superposition, between the two intrinsic degrees of freedom, is discussed. To examine the behavior of the system, ideas from quantum measurement and information theory are employed.