The Compton profiles of W, Ag, and Cu were measured for three scattering angles (30°, 15°, and 10°) using ${}_{}{}^{137}{}_{}{}^{}\mathrm{Cs}$ γ rays. A Monte Carlo simulation was used to reproduce the experimental situation. Double-scattering events are considered in the simulation and subtracted from the single profile when necessary. Good accordance with the theoretical momentum distribution of the electron cloud was observed when relativistic wave functions quoted by Mendelsohn, Biggs, and Mann are used. This accordance was achieved only when the Ribberfors correction of the Compton profile was considered.

We have applied the methods of fast-ion-beam laser spectroscopy (FIBLAS) and laser-rf double resonance to study the 4$p^4$${(\mathrm{}}^3$P)4d ${\mathrm{}}^4$$D_{7/2}$→4$p^4$${(\mathrm{}}^3$P)5p ${\mathrm{}}^4$$D_{7/2}^o$ transition at 642.018 nm in ${}_{}{}^{83}{}_{}{}^{}\mathrm{i}\mathrm{i}$. The effective hyperfine constants of the 4d ${\mathrm{}}^4$$D_{7/2}$ state were measured by radiofrequency magnetic resonance, with the results (in MHz) A=-43.5132(3), B=-294.921(5), and C=-0.0030(6). The FIBLAS results for the 5p ${\mathrm{}}^4$$D_{7/2}^o$ effective hyperfine constants are (in MHz) A’=-145.29(7) and B’=536(2). .AE

We report a comprehensive experimental study of the Sr i autoionizing 5$p_{1/2}$${\mathrm{ns}}_{1/2}$ and 5$p_{3/2}$${\mathrm{ns}}_{1/2}$ J=1 states with n ranging from 10 to 36. We have used an isolated-core-excitation method to determine the energies, autoionization rates, and interseries interaction between the two 5$p_{1/2}$${\mathrm{ns}}_{1/2}$ and 5$p_{3/2}$${\mathrm{ns}}_{1/2}$ channels. A six-channel multichannel-quantum-defect-theory analysis of the data has been performed, and good agreement between the experiment and the theory has been obtained.

Accurate measurements of the x-ray intensity ratio I(Kβ)/I(Kα) from electron-capture radionuclides, using Si(Li) detectors of calibrated line shape, eliminate an existing large discrepancy between experiment and relativistic Hartree-Fock predictions. Small systematic discrepancies in the literature ratios for the mechanisms of photoionization, and electron and proton excitation, are attributed to omission of radiative Auger (RA) satellites in spectrum analysis. With the inclusion of RA peaks in the spectrum fitting, the present data support Scofield’s predictions of I(Kβ)/I(Kα) at the 1% accuracy level, an important conclusion for elemental analysis techniques such as proton-induced x-ray emission and x-ray fluorescence. The resulting radiative Auger intensities also agree quite well with calculations.

The dynamic Stark effect is investigated in a J=0→1→0 three-level ladder system in an atomic beam of natural barium. This system is free of hyperfine structure, which has complicated previous experiments of this type. An intense, actively stabilized cw dye laser was tuned to resonance with the transition between the upper two levels, and a similar, but much less intense, probe laser was scanned through resonance with the transition connecting the lower two levels. Fluorescence arising from transitions out of the middle and upper levels was separately recorded as a function of probe-laser frequency. This allowed us to observe the effects of the strong laser on both the levels which it coupled. The smooth transition from an Autler-Townes doublet to a single light-shifted peak was observed, as well as effects related to coherent population trapping. The resulting profiles were found to be in excellent agreement with theoretical predictions. With a theoretical model extended to incorporate the contributions of the five most abundant isotopes of barium, and other nonideal features of the experiment, it was possible to account for every detail of the observed profiles. Comparing the experimental results with theory also yielded a measurement for the absorption f value for the 6s6p ${\mathrm{}}^1$$P_1$→6$p^2$ ${}_{}{}^3{}_{}{}^{}P_0^{}{}_{}{}^{}$ (608.3 nm) transition in ${}_{}{}^{138}{}_{}{}^{}\mathrm{Ba}$.

We have calculated the steady-state intensity of fluorescence emitted from the middle and upper levels of a three-level (J=0→1→0) atomic ladder system subjected to a weak probe laser tuned to the transition between the lower two levels and a strong laser tuned to the transition between the upper two levels. This configuration of strong and probe lasers is the reverse of that used in previous experimental studies of three-level ladder systems. The configuration studied in this paper allowed the investigation of the population of both levels coupled by the strong laser. In order to predict in detail the results of a real, nonideal experiment carried out on a J=0→1→0 three-level system in a barium atomic beam, the theoretical model must include the effects of the experimental geometry, Zeeman degeneracy, hyperfine structure, and isotope structure. The experiment and the model were restricted to the case where both lasers have the same linear polarization. The method of Ben-Reuven and Klein was used to find an analytic solution to the Bloch equations for the three-level system. Without an analytic or semianalytic solution, the extension of the theory to describe a real experiment would have required a prohibitive amount of computer time.

New bounds to the autoionization and predissociation resonance position and width (which are associated with a complex-coordinate eigenvalue) are derived. An illustrative numerical example is presented.

K-shell photoelectric cross sections are measured by the indirect method in Tb, Ho, Er, and Pt at 84.26 keV. A high-resolution, hyperpure germanium detector and a good-geometry setup are used to conduct a transmission experiment. The superiority of the indirect method over the direct method at low energies is discussed. The results are compared with available theoretical and other experimental values and are in good agreement. The results show a close agreement with the recent and accurate calculations of Scofield.

The fully quantum-electrodynamical model of a two-level atom interacting with a single-cavity mode predicts an atomic evolution whose form is dictated by the discrete nature of the field energy and its statistical distribution. We demonstrate that the revivals of atomic excitation which are the signature of the quantum nature of the evolution are strongly affected by field dissipation even when the damping hardly affects the underlying Rabi oscillations.

Dispersive optical bistability and instabilities leading to period doubling, higher harmonics, and chaos in an all-optical passive quantum system are discussed theoretically and experimentally. These phenomena have been observed for a wide range of operating conditions in ring and Fabry-Perot resonators containing ammonia molecular gas as the nonlinear medium. Laser input intensity, gas pressure, and cavity tuning are the main control parameters in observation of these effects. The experimental results are well modeled by our generalization of standard two-level system theory to include standing-wave, reservoir, and transverse effects.

Intrinsic optical bistability in the scattering and absorption of light from Rayleigh-particle-sized microparticles having an intensity-dependent refractive index is theoretically investigated. For particles near plasmon resonances optical switching also occurs by sweeping the frequency across the resonance at fixed incident intensity above a certain threshold. Several orders of magnitudes of reduction in the switching intensities are possible near sharp resonances, and an optical transistor mode with a very sizable differential gain can be achieved.

We study the stability boundaries for the steady and periodic solutions of the Ikeda delay-differential equation. In the limit of an infinite delay the differential equation reduces to a nonlinear map. For this map there exist two classes of boundaries: one corresponding to subharmonic cascades and the other either to domains of bistability for steady or periodic solutions or to the emergence of stable periodic solutions from chaos. For a finite delay we show that each of the above boundaries splits into an infinite sequence of secondary boundaries. The crossing of the secondary boundaries associated with the subharmonic sequence results in the progressive squaring of the periodic solution. The crossing of a secondary boundary of the bistability sequence results in the addition of a frequency in the transient oscillatory relaxation.

The anomalous coherence functions (ACF) of the radiation fields are studied in detail. The relation of ACF to the source correlation functions is given. Propagation laws for ACF are found. The ACF exhibit a diffractionlike pattern, the nature of which depends on the directions of observation and the spatial extent and initial excitation of the source. If the radiating system is incoherently excited, then ACF vanish. However for any arbitrary system driven by a coherent field ACF are found to be nonzero. ACF are shown to contain information both on the steady-state and transient response of the radiating system. Quantum fluctuations are shown to be important for ACF even when the system is weakly driven, which is in contrast to the ACF for the harmonic oscillator which can be obtained from classical considerations. ACF are also shown to exist in the nonlinear mixing of the electromagnetic fields. The possibility of measuring anomalous coherence functions using phase-conjugation techniques is discussed.

Time-dependent correlation functions and the spectrum of the transmitted light are calculated for absorptive optical bistability taking into account phase fluctuations of the driving laser. These fluctuations are modeled by an extended phase-diffusion model which introduces non-Markovian effects. The spectrum is obtained as a superposition of Lorentzians. It shows qualitative differences with respect to the usual calculation in which phase fluctuations of the driving laser are neglected.

A monochromatic laser is shown to be capable of inducing a bound state and multiple metastable states not originally present in the field-free spectrum of a bound-continuum system. For the bound state to exist, the field intensity must be larger than a certain frequency-dependent critical value. The widths of the metastable states are found to be in general proportional to renormalized field intensities rather than the physical field intensity. The energies can be classified as being in the metastable or unstable regimes, depending on whether the observed widths are smaller or larger than the corresponding ‘‘bare’’ widths predicted by perturbation theory. The relation of the Fano or laser-induced ‘‘autoionization’’ states to the scattering states is also demonstrated.

A formalism is presented to treat the effects of finite-bandwidth excitations on the fluorescent spectra and second-order intensity-correlation functions in optical double resonance. It is assumed that the bandwidth arises from the phase and/or amplitude fluctuations in the fields driving a three-level atom. Under the conditions that one or both these fields are intense, secular approximation and the theory of multiplicative stochastic processes are invoked to derive a Markovian master equation for the atomic-density operator averaged over both phase and amplitude ensembles. The quantum regression theorem is used to derive analytical expressions for the fluorescent spectra and the second-order intensity-correlation functions.

One-, two-, and five-dimensional Fokker-Planck equations for absorptive bistability are solved with use of small-noise asymptotic expansions, which are different from Gaussian linearized analysis. The cases studied are the bifurcation point for the start of hysteresis, where there is critical slowing down and the fluctuations are large, and the evolution of a steady-state distribution when the input field has a step change. The time evolution of the probability distribution is calculated.

We consider the effect on a generic period-doubling bifurcation of a periodic perturbation, whose frequency ${\omega }_1$ is near the period-doubled frequency ${\omega }_0$/2. The perturbation is shown to always suppress the bifurcation, shifting the bifurcation point and stabilizing the behavior at the original bifurcation point. We derive an equation characterizing the response of the system to the perturbation, analysis of which reveals many interesting features of the perturbed bifurcation, including (1) the scaling law relating the shift of the bifurcation point and the amplitude of the perturbation, (2) the characteristics of the system’s response as a function of bifurcation parameter, (3) parametric amplification of the perturbation signal including nonlinear effects such as gain saturation and a discontinuity in the response at a critical perturbation amplitude, (4) the effect of the detuning (${\omega }_1$-${\omega }_0$/2) on the bifurcation, and (5) the emergence of a closely spaced set of peaks in the response spectrum. An important application is the use of period-doubling systems as small-signal amplifiers, e.g., the superconducting Josephson parametric amplifier.

It is suggested that complex problems in ultrasubmicrometer electronics research may greatly benefit from use of the path-integral technique. The use of the Weyl-Wigner formalism of the quantum dynamics of electrons in solids provides a rigorous and straightforward derivation of the path integral in solid-state physics, both from the single-particle and from the many-body field-theoretical description of electron dynamics, without the need to postulate a priori the isomorphism between quantum operators and c-numbers of the base field. A rigorous construction of the path integral in many-body solid-state band theory necessitates a two-stage Weyl correspondence between quantum operators and c-numbers of the base field, namely, the Weyl correspondence of the base field of ‘‘lattice-space’’ particle-dynamical variables and that of the continuum many-body field-dynamical variables.

A detailed theoretical and experimental investigation is presented of the excited-level population distribution in a Li-Ne vapor under excitation by a photoionization electron source. This source produces a subnanosecond burst of hot ($T_e$∼20 eV) electrons with a peak density in excess of 5×${10}^{15}$ ${\mathrm{cm}}^{\mathrm{-}3}$. The electrons are generated as a result of photoionization of Ne atoms by x rays emitted from a plasma produced by a 100-mJ laser pulse of 600 ps duration. Measurements of Li(1$s^2$2p)-atom density, and of electron density, have been performed with subnanosecond time resolution under various conditions of excitation. A comprehensive rate-equation model is described and its predictions are seen to be in good agreement with experiment. It is shown that the population distribution in the Li-Ne vapor is strongly influenced by recombination. Under the conditions of these experiments, rates for this process as high as 3×${10}^9$ ${\mathrm{s}}^{\mathrm{-}1}$ were observed.