The solution of a model for adhesive hard spheres is obtained within the mean-spherical approximation. The adhesive part of the potential is modeled as the limit of a Yukawa tail when both the amplitude and the inverse range tend to infinity. Use is then made of the analytical solution of the Ornstein-Zernike equation with a Yukawa closure, developed by Waisman, Hoye, Stell, and Blum. The system presents a liquid-gas phase transition, and the critical exponents γ and δ are those of the spherical model.

A combination of semiclassical arguments and random-matrix theory is used to analyze transition strengths in quantum systems whose associated classical systems are chaotic. The mean behavior is found semiclassically while the local fluctuations are characterized by a Porter-Thomas distribution. The methods are tested numerically for a system with two degrees of freedom, the coupled-rotators model. The deviations of the strength distribution from a Porter-Thomas one when the system is nonchaotic are also investigated. It is found that the distribution gets gradually wider as the classical system becomes more regular.

A family of approximations to the atomic electron density at the nucleus, ρ(0), has been derived using the Baker-Gammel approximants and the cusp condition for ρ(r). The quality of approximations that do not invoke the cusp condition deteriorates for atoms with large Z. On the other hand, the inclusion of the cusp condition results in an approximate formula that provides ρ(0) within less than 3%, requiring 〈$r^{\mathrm{-}2}$〉, 〈$r^{\mathrm{-}1}$〉, Z, and N as input. This improves the result by M. Hoffmann-Ostenhof, T. Hoffmann-Ostenhof, and W. Thirring [J. Phys. B 11, L571 (1978)].

The possibility of detecting low-baryon-number lumps of strange matter (strangelets) by their abnormal (lower-energy) atomic x rays is suggested; this would be accomplished by inducing inner-shell electron vacancies in proton-strangelet collisions. The energy shift in the x rays of low-mass ‘‘strange atoms’’ (Z≤104) is estimated.

Electron-impact excitation of the excited vibrational levels of the $c_4^{\mathcal{’}}$ ${}_{}{}^1{}_{}{}^{}\Sigma _u^{+}{}_{}{}^{}$ state of the nitrogen molecule has been studied. We measure the electron-impact optical emission cross sections of the (1,2), (4,0), and (4,1) vibration bands of the $c_4^{\mathcal{’}}$→a electronic transition of the nitrogen molecule and compare them with the direct electron-impact cross sections of the $c_4^{\mathcal{’}}$(v’) vibrational levels reported in the literature. The Franck-Condon factors between the ground vibrational level of the X ${}_{}{}^1{}_{}{}^{}\Sigma _g^{+}{}_{}{}^{}$ ground electronic state and the various vibrational levels of $c_4^{\mathcal{’}}$ have been calculated and compared with the electron-impact cross sections. The excitation cross sections of the v’=4 level of $c_4^{\mathcal{’}}$ are several orders of magnitude higher than predicted by the Franck-Condon picture. This discrepancy is due to the perturbations of the $c_4^{\mathcal{’}}$(v’=4) level by the b’ ${}_{}{}^1{}_{}{}^{}\mathrm{\Sigma }_{\mathrm{u}}^{+}{}_{}{}^{}$ state.

The muonic Coulomb capture ratio A(${\mathrm{H}}_2$,Ar) has been measured in two different ${\mathrm{H}}_2$-Ar gas mixtures using two different methods of evaluation based on the muon transfer from hydrogen. The measured ratios agree with each other, but disagree with the corresponding pionic capture ratio and also with the ratios calculated from muonic and pionic A(He,Ar) and A(He,${\mathrm{H}}_2$) capture ratios. The large discrepancies might be related to unsolved problems in muon transfer.

We present in this paper a coupled-cluster method for the calculation of the response of properties of a system of various orders. This uses a multiconfigurational model space thus making it suitable for open-shell or quasidegenerate situations. We present the basic equations and the hierarchy for generating higher-order response.

Resonances for rearrangement collisions (reactive scattering) involving the two dissociative attachment processes, e+HCl→H+${\mathrm{Cl}}^{\mathrm{-}}$ and e+${\mathrm{H}}_2$→H+${\mathrm{H}}^{\mathrm{-}}$, are examined. It is shown from the Argand-diagram representation of transition amplitudes that strong resonance is present in the former but not in the latter. That is, the strong resonance is evidenced by the clear exhibition of a phase change by π in a counterclockwise direction in the Argand diagram as the collision energy increases. Such a manifest phase change is absent in the dissociative attachment process of e+${\mathrm{H}}_2$→H+${\mathrm{H}}^{\mathrm{-}}$. This is attributed to the presence of equally strong, direct, and resonant scattering processes, and to the strong influence of mutually destructive interference.

The stopping power of matter for deuterons is calculated without the explicit use of the condition γm≪$M_d$, where m and $M_d$ are the rest masses of the electron and the deuteron, γ=(1-${\beta }^2$${)}^{\mathrm{-}1/2}$, and v=βc is the speed of the incident deuteron. The effects of admixing isobar configurations into the deuteron wave function as well as contributions to the respective deuteron form factors are included. The contributions of the various effects to the stopping powers of aluminum, copper, and lead are evaluated numerically up to γ${=10\mathrm{}}^4$, where they decrease the stopping power by about 26% in comparison with Bethe’s relativistic theory. The results are found to be insensitive to the various nucleon-nucleon potentials.

A model describing the relaxation of elementary excitations consisting of two oscillators interacting through a nonlinear coupling is discussed. Numerical solutions are shown to display motional narrowing.

Dielectronic-recombination cross sections are estimated for ions of the B isoelectronic sequence (${\mathrm{N}}^{2+}$, ${\mathrm{O}}^{3+}$, and ${\mathrm{F}}^{4+}$) in which the 2s→2p excitation is involved during the initial capture. Different Auger channels for the core states ${}_{}{}^2{}_{}{}^{}\mathrm{P}$, ${}_{}{}^2{}_{}{}^{}\mathrm{D}$, ${}_{}{}^2{}_{}{}^{}\mathrm{S}$, and ${}_{}{}^4{}_{}{}^{}\mathrm{P}$ are explicitly included. An approximate field-enhancement factor for the maximum mixing is given.

The distribution of internal states in ${\mathrm{Na}}_2^{+}$ arising from the associative ionization (AI) collisions, Na(3p ${}_{}{}^2{}_{}{}^{}\mathrm{P}_{3/2}^{}{}_{}{}^{}$)+Na(3p ${}_{}{}^2{}_{}{}^{}\mathrm{P}_{3/2}^{}{}_{}{}^{}$)→${\mathrm{Na}}_2^{+}$+${\mathrm{e}}^{\mathrm{-}}$, probes the general shape of the potential curves on which the collision takes place. We compare the internal-state distribution extracted from experimental data to those calculated from two sets of recently published potential curves. The results of the comparison indicate that the incoming channels for the AI process follow attractive potentials in the nuclear motion.

A method is given to evaluate directly the ‘‘destruction’’ terms which occur in the non-Markovian theory of collisional redistribution when two photon events occur within a single collision. It shows that these terms, which are important for large detunings, may be expressed as separate stationary-phase (quasistatic) principal-value (antistatic) components. In contrast to previous work, the method easily extends to take into account atomic-state degeneracy.

Experimental results for the static polarizabilities of the 0 $0^0$ 1 and 0 $2^0$ 0 states of ${\mathrm{CO}}_2$ are compared with those derived from calculated results. The discrepancy between the experimental and theoretical differences between the anisotropic and isotropic polarizabilities is discussed.

Calculations that employ a relativistic time-dependent local-density approximation to atomic absorption are used to examine a recent claim to the observation of giant quadrupolar resonances in the electron-energy-loss spectrum of Ce metal near the 4p edge. We confirm the existence of 4p→4f resonances in this energy range but find the polarization effects much smaller than in typical giant dipole resonances.

Various semiclassical approaches to the quadratic Zeeman effect in the l-mixing region are interpreted in a physically transparent fashion and presented as a short summary report.

We report on a linear-stability analysis of a three-level, resonantly optically pumped, homogeneously broadened, single-mode laser. We identify the relatively simple nature of the local bifurcations on the nonlasing branch comprising pitchfork, Hopf, and codimension-2 bifurcations. Their use is demonstrated in identifying regions of parameter space in which we may expect steady, periodic, and more complex dynamical behavior.

A representation is introduced in which a state of a radiation field is characterized by a function of a parameter which can be any arbitrary number. This functional representation of a field state offers a convenient means of classifying squeezed states and calculating their variances. Some new squeezed states are found from an analysis based on this representation.

Analytic approximations for the third- and higher-order direct correlation functions of uniform classical liquids are presented. These are derived from a weighted-density approximation for the one-particle direct correlation function of a nonuniform liquid which requires as input only the two-particle function of the corresponding uniform liquid. The three-particle result is shown to have the same accuracy as two recently proposed approximations, but has a much simpler form. The four- and five-particle results are new, and in principle can be tested by simulation methods.

Rydberg states in highly stripped fast oxygen and neon ions are formed in the interaction with thin carbon foil and gas targets. They are ionized in the field of an electrostatic parallel-plate spectrometer and produce pronounced structures in the electron energy spectra at apparent energies higher than the cusp peak. The measured electron yield shows marked oscillatory structures in the dependence of the strength of an additional weak electric field in the drift space between target and spectrometer. Fourier analysis of the data reveals the presence of an asymmetric band of fundamental frequencies and contributions from higher harmonics. The oscillations are interpreted in terms of quantum interferences among Stark states which coherently develop in the weak drift-space field. A predominant influence of the experimental arrangement on the shape and the position of the Rydberg structure in the electron spectrum is found through analysis of the data on the basis of a program which calculates the electron trajectories through the fringe fields of the detector. The analysis also reveals that the dependence of the oscillation periods on the detector field strength is influenced by fringe-field effects. The absolute values for the periods and the ionization process in the detector are explained in the frame of a simple model and conclusions are drawn about the contribution of experiments of the present type in understanding the mechanisms of Rydberg formation.