Presently, quantal applications of atom–diatomic-molecule rearrangement collision processes to information-theoretic analysis have been limited to ab initio (exact close-coupling) methods. By taking into account symmetry consideration, a convenient expression for the analysis of rotational surprisal is deduced for the rearrangement collision process of H+${\mathrm{D}}_2$→HD+D. The dependency of rotational surprisal on collision energy and initial (reactant) rotational quantum state is examined. From a simple distorted-wave perturbation approach we find the propensity of near-linear surprisal at low collision energies and of deviation from linearity at higher collision energies.

Total-cross-section results for excitations of n ${\mathrm{}}^1$S and n ${\mathrm{}}^1$P (n=2–6) states of several heliumlike ions from the 1 ${}_{}{}^1{}_{}{}^{}S$ ground state are reported in this paper for energies near threshold to above 5 times the threshold energy. These results are obtained using a reliable distorted-wave polarized-orbital approach where distortions are included due to static, polarization, and exchange effects appropriately as desired in both the initial and final channels of the distorted waves. Sensitivity of the results with respect to different choices of ion-target wave functions (such as hydrogenic, Hartree-Fock, and configuration-interaction types) in the present model is also examined. The results are compared with other available theoretical estimates.

Multiphoton ionization via four-photon excitation of high-lying Rydberg states in xenon and krypton has been studied. The p and f series leading to the ${}_{}{}^2{}_{}{}^{}\mathrm{P}_{3/2}^{}{}_{}{}^{}$ ionization limits as well as the p’ and f’ autoionizing levels leading to the ${}_{}{}^2{}_{}{}^{}\mathrm{P}_{1/2}^{}{}_{}{}^{}$ limits have been recorded for both gases. Lower members of the p series in xenon are resolved into p${\left[\mathrm{}\right(5/2\left)\mathrm{}\right]}_2$, p${\left[\mathrm{}\right(3/2\left)\mathrm{}\right]}_2$, and p${\left[\mathrm{}\right(1/2\left)\mathrm{}\right]}_0$ sublevels. Ionization potentials and quantum defects are obtained by a least-squares fitting of the data to the standard Rydberg formula.

The authors have performed an extensive series of measurements of the infrared rotation-vibration spectrum of the negative molecular ion ${}_{}{}^{14}{}_{}{}^{}\mathrm{NH}_{}^{\mathrm{-}}{}_{}{}^{}$. A total of 114 transitions in the P, Q, and R branches of the fundamental band near 3000 ${\mathrm{cm}}^{\mathrm{-}1}$ have been measured with an accuracy (1 standard deviation) of 0.01 ${\mathrm{cm}}^{\mathrm{-}1}$. The resolution is much higher (7 MHz), enabling us to resolve hyperfine structure. Autodetachment linewidths have also been measured. The electron affinity of NH has been measured with a precision a thousand times higher than previous work: $E_{\mathrm{EA}}$(NH)=0.374 362±0.000 005 eV. Our data agree with earlier measurements of the R branch and include the first high-resolution measurements of the Q and P branches. We have observed rotationally excited metastable states as much as 1.8 eV above the autodetachment threshold. A least-squares fit to the transition frequencies has been performed, using an effective Hamiltonian with a sextic term. The predictions of the best previous work, extrapolated to high J, disagree by as much as 10 ${\mathrm{cm}}^{\mathrm{-}1}$, or one thousand times the experimental uncertainty. This paper more than doubles the number of measured transition frequencies in this species.

Theoretical transition probabilities for kf-nd and mp-nd transitions in Ga(k=4–6, Ga i (k=4–6, m=4–7, and n=4–8) are reported together with lifetimes for the first five members of the 4$s^2$nd ${}_{}{}^2{}_{}{}^{}D$ series. Mixing with 4s4$p^2$ ${}_{}{}^2{}_{}{}^{}D$ is found to be very important. The sensitivity of the nd ${}_{}{}^2{}_{}{}^{}D$ lifetimes to the position of this perturber is discussed, together with the oscillator strength trend for the transitions from the nd ${}_{}{}^2{}_{}{}^{}D$ series, n=4–11, to the ground state. The calculated lifetimes are in good agreement with recent laser experiments.

Previously unknown uranium i energy levels have been classified according to configuration using pattern-recognition techniques. Four features, the energy level, Landé g factor, quantum number J, and ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ isotope shift, have been used to describe each level. Additionally, a fifth feature, the ${}_{}{}^{234}{}_{}{}^{}\mathrm{U}$ isotope shift, has been employed to describe most levels. Thirty-seven levels have been assigned with high certainty. In addition, four-feature classification versus five-feature classification is discussed.

Photoelectron satellite branching ratios and asymmetry parameters have been measured for photoionization of atomic He to ${\mathrm{He}}^{+}$(n), where n=3–5, at a few photon energies near the satellite thresholds. The n=3 and n=4 satellite branching ratios relative to the n=1 main-line cross section exhibit behavior similar to that previously observed for the ${\mathrm{He}}^{+}$(n=2) satellite. The asymmetry parameter β shows progressively more negative values as n increases, supporting a prediction by Greene [Phys. Rev. Lett. 44, 869 (1980)] for the threshold behavior of the He satellites.

The neon spectrum is of considerable laser-physics interest, yet few measurements of its spectral line broadening and shift parameters have been performed. In this investigation the Stark widths and shifts of twenty Ne lines originating from several multiplets were measured as functions of electron density and temperature in the ranges (0.15–1.40)×${10}^{23}$ ${\mathrm{m}}^{\mathrm{-}3}$ and (1–2.5)×${10}^4$ K, respectively. The light source was the plasma of an electromagnetically driven ‘‘T tube’’ operating in a mixture of neon and argon in the ratio 2:5 in order to avoid self-absorption. The electron density was measured by single-wavelength laser interferometry using the visible λ=632.8 nm transition of a He-Ne laser, and the electron temperature from the Boltzmann slope of several Ar spectral lines with estimated errors of ±7% and ±10%, respectively. The obtained measured Stark widths (w) and shifts (d) with estimated errors of ±15% are compared with the existing experimental and theoretical data. All together, Stark widths and shifts data are used to demonstrate the nature of Stark broadening and shift dependence on the upper-level ionization potential of the corresponding line in a transition array.

Using the isolated-core-excitation method we have measured the energies and widths of the three Sr J=3 autoionizing 5pnd Rydberg series for n=11–36. We have fitted our data to a six-channel multichannel quantum-defect theory model reproducing the observed energies, widths, and interactive excitation spectra for the three series. In addition, the effect of the bound 4d6s ${\mathrm{}}^1$$D_2$ and 4d6s ${}^3$$D_2$ perturbers, which mix the bound 5snd ${}_{}{}^1{}_{}{}^{}\mathrm{D}_2^{}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{D}_2^{}{}_{}{}^{}$ states, on the excitation spectra has been observed and accounted for.

A systematic search for relativistic Cooper minima (CM) has been carried out for all allowed bound-free transition channels, from all occupied subshells of all ground-state atoms with Z between 1 and 105, within the independent-particle approximation (Dirac-Slater-type calculation). The generality and systematics of relativistic effects on CM, including their splitting and continued occurrence high above threshold for high Z, is surveyed. It is also found, as a general feature, the photon energy CM trajectories (photon energy of occurrence as a function of Z) are smooth curves, while the corresponding electron energy CM trajectories are not. This can be understood in terms of the role of outer screening and the variation of binding energy with the ‘‘irregular’’ subshell filling order.

The generality and systematics of ionic Cooper minima, primarily found for ${\mathrm{ns}}_{1/2}$→ε$p_{3/2}$ and ${\mathrm{np}}_{1/2}$→ε$d_{3/2}$ bound-free transitions, are studied within the relativistic central-field independent-particle approximation. For these two transitions the full physical region (and beyond) in ions or atoms of nuclear charge Z and number N of bound electrons is considered. (Other transitions are discussed, for ground states and some excited states.) The existence domain of Cooper minima in the N-Z plane is determined. For very-high-Z elements point-Coulomb relativistic Cooper minima are found for both transitions. It is argued that the relativistic shift in the phase difference between initial and final states is responsible.

Exact calculations are presented of the properties of nonlinear p-polarized waves propagating along the plane boundary between a nonabsorbing, optically self-focusing, nonlinear dielectric and a nonabsorbing positive, or negative, linear dielectric. A nonlinear polarization is used that arises from a number of causes for both Kerr-like and non-Kerr-like saturating media. In the results given here the linear dielectric is a metal, if negative, and is glass if positive. It is found that the variation of the power flow along the guiding surface with effective index, for negative linear dielectrics, will always exhibit a maximum. For data corresponding to copper bounded by, for instance, a self-focusing nonlinear semiconductor, access to this maximum involves such a large change in the refractive index of the nonlinear material, that it is of no practical interest. In the visible better matching of the metal to a nonlinear material can, in principle, be achieved so this maximum may be reached for fairly modest nonlinear changes in the refractive index. A detailed comparison is made with approximations that are based upon a curtailed form of nonlinearity. At low frequencies, for modest nonlinear changes in the refractive index, the dependence of the power flow curve upon the effective guide index is fairly close to several of the earlier published theories. These include a well-known approximation in which the transverse field component is assumed to be dominant. The neighborhood of the maximum, and beyond, becomes accessible at higher operating frequencies and significant differences from earlier approximations may then occur. For positive linear dielectrics the exact theory shows a strong similarity to many more approximate ones, as expected, but the difference between the TM and TE surface wave behavior cannot be discounted. We present several sample calculations of the power flow together with detailed plots of the field components, the magnitude of the nonlinearity, the effect of nonlinearity, and the behavior of the first integral.

We consider the effect of periodically modulated cavity losses on the bifurcation diagram of the laser rate equations. The double limit of very slow atomic inversion relaxation and small modulation amplitude is investigated. Our control parameter λ is the ratio of the damped oscillation frequency of the rate equations (at zero modulation amplitude) to the forcing frequency. We concentrate on the case of pure resonance (λ=1) and the first subharmonic resonance (λ=(1/2)) because they are most representative of the effects of the periodic control. We first reformulate the laser problem as a weakly perturbed conservative system and construct harmonic and subharmonic large-amplitude periodic solutions by a regular perturbation analysis. The conditions for the existence of these solutions are analyzed and evaluated numerically. We show that harmonic and subharmonic solutions may coexist. We then determine a small-amplitude periodic solution oscillating at the forcing frequency. We show that perturbations of this basic state lead to slowly decaying quasiperiodic oscillations except in the vicinity of the critical points λ=(1/2) and 1. In the first case, subharmonic bifurcation may occur and the period of the oscillations suddenly doubles. In the second case, bistability of periodic solutions is observed.

We study the stability of optical bistable elements against holding-field noise by considering the specific case of a purely dispersive Kerr medium. For small devices, i.e., those for which the round-trip time is small compared to the material-response time, we show that operation of an optical switch with a holding-field intensity a few percent away from the switching value will not be subject to problems due to the noise in the holding laser. This is due to the extremely rapid increase of the average time between noise-induced switching events as the distance, in intensity, from the switching point increases. White noise or Ornstein-Uhlenbeck noise models are not sufficiently smooth for a correct description of this problem, and so we use a more elaborate colored-noise model to evaluate the diffusion constant in the Fokker-Planck equation for the nonlinear phase shift. The time between switching events is then obtained by solving a first-passage-time problem.

We examine the nonlinear response of a liquid suspension of microspheres to moving electromagnetic gratings. Such gratings are associated with the overlap of pairs of nearly degenerate laser fields in coherent beam combination and four-wave-mixing applications. The Brownian suspension also serves as a useful model Kerr medium for which the response to arbitrarily strong fields is obtained. This response includes the formation of higher-order particle-density gratings oscillating at harmonics of the frequency difference between the incident fields. It is found that the first-order grating, which oscillates at the fundamental frequency, will coherently scatter the high-frequency wave into the low-frequency beam. Expressions for the particle current, power dissipation, and entropy of grating formation are obtained.

A recently developed nonlinear complex eikonal approximation which was previously employed to the study of dispersively nonlinear resonators is applied to absorptively nonlinear resonator configurations. The nonlinear absorption is introduced phenomenologically, encompassing a large variety of intensity-dependent absorption mechanisms. Conditions for obtaining optical bistability are derived. Dynamically increasing absorption was not considered, and optical bistability in free propagation was not obtained.

A model of fluid-argon–solid-${\mathrm{CO}}_2$ interface is investigated by means of density-functional (DF) -theory and modified-hypernetted-chain (MHNC) calculations. Both theoretical approaches predict complete wetting of the ${\mathrm{CO}}_2$ wall from the bulk Ar vapor when this approaches the coexistence region. At a bulk vapor density $n_B$${\sigma }^3$=0.08 and for an assigned wall-fluid coupling strength, the DF and MHNC estimates of the temperature for which complete wetting occurs are very close to each other ($T^{\mathrm{*}}$≃1.16), and to the coexistence temperature of the homogeneous bulk phase obtained through independent DF and MHNC calculations. The DF results also show the existence of a prewetting transition, very close to the coexistence line, and of a ‘‘surface spinodal line,’’ that is a set of points near and inside the coexistence region, at which transverse correlations in the fluid near the wall diverge, while the adsorption or coverage remains finite. The MHNC does not have convergent solutions in regions too close to coexistence so that it is hard to detect the very short prewetting line; however, the extrapolated behavior of the transverse correlations and coverage, which both show a diverging trend on approaching a well-defined temperature, and of the density profile whose features, far from the wall, faster and faster herald in the approach to coexistence, all point to the occurrence of complete wetting. Moreover, in agreement with DF results, transverse correlations also show a diverging trend inside the coexistence region while the coverage remains finite, thus confirming the existence of a surface spinodal line.

A nonresonant nature of wave-particle interaction is clarified from the viewpoint of quantum mechanics. The interaction of particles and quasiparticles can be described by the use of transition probability which is found to have both resonant and nonresonant contributions. The resonant transition probability is known as Fermi’s golden rule, which is now supplemented by the nonresonant contribution, resulting in the proper conservation of energy and momentum in the particle-quasiparticle system.

An extension of Waisman’s model of a binary-fluid mixture is considered. In this equal-diameter mixture particles interact via a hard core for r<1 and Yukawa tail potentials $K_{\mathrm{ij}}$exp[-z(r-1)]$r^{\mathrm{-}1}$ for r>1. The symmetrical mixture consists of two species of particles, each with the same number density. For like particles $K_{11}$=$K_{22}$ and unlike particles are specified by $K_{12}$. We solve analytically the mean-spherical-approximation equations for this model and show that two kinds of phase transition may occur in it. Namely, when $K_{11}$<-$K_{12}$ a liquid-gas-type phase transition is possible whereas in the case $K_{11}$<$K_{12}$ a phase-separation-type transition may occur. The separation line between the two liquid phases is exactly a straight line in the temperature-versus-density coordinate system. The liquid-liquid transition for this system is compared with the corresponding transition for the quasilattice model. If the equation $x_1$$K_{11}$-($x_1$/B -$x_2$)$K_{12}$-$x_2$$K_{22}$=0 is satisfied, the equal-diameter Yukawa system for a general composition $x_i$ can also be solved analytically. Based on this finding, we propose an approximate extension of the equal-diameter Yukawa model to arbitrary values of $K_{\mathrm{ij}}$ and all compositions.

We propose a model describing the various atomic species existing in a dense plasma; a species is a neutral atom with a given frozen configuration in the bound spectrum, surrounded by a screening cloud of free electrons in thermal equilibrium. First, a prescription is given to calculate these atomic species (bound spectrum, electron density, energy). A second part is concerned with the study of bound-bound electronic transitions; the transition energy is determined in terms of ‘‘modified effective one-particle energies’’ for the final and initial bound states. Some numerical applications are presented, proving that the model may be useful in calculating properties relative to various non- equilibrium situations. Finally, turning back to total thermal equilibrium, we define ‘‘average atomic species’’ for any ionization state $Z^{\mathrm{*}}$ and calculate their respective weight; we also compute the average value of $Z^{\mathrm{*}n}$ and its fluctuations.