We present a detailed analysis of the quantum-nondemolition (QND) properties of a measurement scheme employing coherently driven three-level atoms in the Λ or cascade configuration inside an optical cavity. We propose to use a strong signal field to empty one of the transitions and dress the signal-transition levels. The atoms become transparent for the signal beam, which sees a ‘‘ghost transition.’’ When a probe is applied and tuned to the vicinity of one of the light-shifted levels, the probe phase is extremely sensitive to fluctuations of the signal intensity. This enhances the QND coupling and enables the system to operate at lower cooperativities.

Investigations of a 96.9-nm laser in neutral cesium are described. Theoretical and experimental evidence is presented for the laser level designation and pumping mechanism. Measurements of the laser output are given, including saturated pulse energy, temporal profile, spatial profile, transition wavelength, gain cross section, and the variation of small signal gain with operating parameters. Comparisons of the temporal and spatial behavior of the 96.9-nm laser emission with respect to resonance line emission from ionic Cs are also presented.

The time evolution of the ground state of a one-dimensional hydrogen atom in the intense laser pulse is studied directly in momentum space. A finite matrix representation of operators is developed to solve nonperturbatively the time-dependent Schrödinger equation. We find that some numerical limitations in coordinate space of above-threshold ionization (ATI) can be overcome, and clear physical interpretations of the numerical data are possible. Both the ATI and harmonic-generation spectra are obtained. The correlations between these two multiphoton phenomena are discussed.

We present a fully canonical quantization scheme for the electromagnetic field in dispersive and lossy linear dielectrics. This scheme is based on a microscopic model, in which the medium is represented by a collection of interacting matter fields. We calculate the exact eigenoperators for the coupled system and express the electromagnetic field operators in terms of them. The dielectric constant of the medium is explicitly derived and is shown to satisfy the Kramers-Kronig relations. We apply these results to treat the propagation of light in dielectrics and obtain simple expressions for the electromagnetic field in the medium in terms of space-dependent creation and annihilation operators. These operators satisfy a set of equal-space commutation relations and obey spatial Langevin equations of evolution. This justifies the use of such operators in phenomenological models in quantum optics. We also obtain two interesting relationships between the group and the phase velocity in dielectrics.

The Q function in the undamped Jaynes-Cummings model for a coherent initial state in the rotating-wave approximation is investigated. By applying the method of steepest decent and saddle-point integration in the limit of high photon numbers, closed analytic expressions for the Q function at different times are given, from which analytic expressions for the Rabi frequency, revival times, envelope shapes of the inversion, beat frequencies, etc. are derived. As Eiselt and one of us have shown [J. Eiselt and H. Risken, Phys. Rev. A 43, 346 (1991)], the Q function first splits into two peaks which counterrotate in the complex plane and then collide on the opposite side of the plane. This behavior of the Q function leads to an interpretation of the collapses and revivals of the Rabi oscillations and a better understanding of expressions for the Rabi frequency, revival times, envelope shapes of the inversion, beat frequencies, etc. The results are generalized to N-photon processes; in particular, the cases N=2 and 4 are treated in some detail.

We present a formal quantum-mechanical treatment of the damping and fluctuations of a generic radiator atom due to collisions with foreign gas atoms. By working in the Heisenberg picture, the fluctuating noise sources are identified with the damping. Under the same approximations as the conventional line-shape broadening theory in the impact (Markov) approximation, the fluctuation-dissipation theorem is satisfied in the form of the conservation of an equal-time commutator for the atomic operators. The implications of this type of approach for the quantum theory of light propagation in an active medium is addressed. Simple cases for two-level and three-level Λ-type systems are given explicitly.

When a Rydberg state is suddenly excited to an autoionizing Rydberg state by a short-pulse core-electron excitation, a shock wave is created in the Rydberg electron’s wave function. This shock wave originates at small r, at the excited core, and propagates outward. This wave-function disturbance is best illustrated by the Rydberg wave function in momentum space, where the autoionization process can be seen as a filtering process that reduces the high-momentum, outgoing wave function.

The interaction of a two-level atom with a single mode of the radiation field is examined. The cavity mode is damped by coupling to a reservoir in a squeezed state, and the atom is also driven by an external laser field. A master equation for the atomic density operator in the bad-cavity limit is derived. The effect of the squeezing in the stationary population inversion and in the resonance spectrum of the light emitted by the atom into the background modes is studied. The results are compared with the numerical solution of the full master equation for the atom-plus-cavity mode-density operator.

The quantum-stochastic-differential-equation formulation of driven quantum-optical systems is carried out in the interaction picture, and quantum stochastic differential equations for wave functions are derived on the basis of physical principles. The Ito form is shown to be the most practical, since it already contains all the radiation reaction terms. The connection between this formulation and the master equation is shown to be very straightforward. In particular, a direct connection is made to the theory of continuous measurements, which leads directly to the method of quantum-jump simulations of solutions of the master equation. It is also shown that all conceivable spectral and correlation-function information in output fields is accessible by means of an augmentation of the simulation process. Finally, the question of the reality of the jumps used in the simulations is posed.

Wave-function simulation of the master equation in terms of quantum jumps is illustrated for vacuum, thermal, and squeezed reservoirs. We discuss simulation techniques for (i) atomic density matrices, and resonance fluoresence and weak-field absorption spectra of atoms, (ii) decay of a two-level system in a squeezed vacuum, and (iii) a strongly coupled atom-cavity system driven by thermal light.

We derive the modifications of the quantum fluctuations of a coherent field after it has interacted with an optical cavity containing an ensemble of two-level atoms. The fluctuations in the output field are separated into two parts: the first one is linked to the parametric transformation of the fluctuations of the incoming field by the atomic medium; the second one is associated with the resonance fluorescence of the atoms driven by the mean intracavity field and coupled with the empty modes of a bath field. We calculate the squeezing spectra and we compare them to the ones obtained with Kerr media having similar dynamic nonlinearities.

The angular distributions of electrons elastically scattered from ${\mathrm{H}}_2$O have been measured by electron impact using a modulated crossed-beam method. The energy and angular range measured were from 30 to 200 eV and 12° to 156°, respectively. The present results show a high backward scattering for low incident energies, but this falls off for high incident energies. The present results are in qualitative agreement with the measurements of Danjo and Nishimura [J. Phys. Soc. Jpn. 54, 1224 (1985)] and in quantitative agreement with the measurements of Katase et al. [J. Phys. B 19, 2715 (1986)]. Agreement between the present results and the calculation of Jain, Tripathi, and Jain [Phys. Rev. A 37, 2893 (1988)] is good except at 200-eV impact.

The algebra of observables inherent in the Nambu formalism [Phys. Rev. D 7, 2405 (1973)] for a generalization of classical Hamiltonian dynamics is investigated. A consistency requirement of time evolution of the Nambu bracket leads to a five-point identity. Two types of algebras are possible at the classical level. Their composition properties under a tensor product are considered and the physical implications are analyzed. A quantum generalization of these algebras is shown to be impossible.

A pair of spin-j particles, prepared in a singlet state, move away from each other and are examined by two distant observers. A simple experimental procedure can produce a 24% violation of a Bell inequality, for arbitrarily large j.

We use fourth-order many-body perturbation theory to calculate the rotational and vibrational constants of CaC. These spectroscopic constants should be useful in the possible laboratory or astronomical observation of this metal carbide.

The stability of weakly bound ground states, with zero total angular momentum, in three-body Coulomb systems with unit charges, is studied by means of highly accurate variational calculations. Weakly bound ground states are predicted for a number of systems, including ${\mathit{d}}^{+}$${\mathit{t}}^{+}$${\mathit{p}}^{\mathrm{-}}$, ${\mathit{t}}^{+}$${\mathit{K}}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$, ${\mathrm{\pi }}^{+}$${\mathrm{\mu }}^{+}$${\mathrm{\mu }}^{\mathrm{-}}$, and ${\mathrm{\pi }}^{+}$${\mathrm{\mu }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$.

Results of a precise calculation of the Coulomb self-energy for states with n=1 and 2 for nuclear charge Z in the range 5–110 in increments of 5 are given. Results are also given for some elements that are of particular experimental interest. These values provide improved accuracy over previous calculations.

K-shell x-ray production cross sections for Na, Mg, Al, Si, Cl, K, Ca, and Ti bombarded by ${}_{}{}^4{}_{}{}^{}\mathrm{He}_{}^{+}{}_{}{}^{}$ ions in the energy range 1.0–2.5 MeV have been measured using thin targets. The ionization cross sections deduced are compared with various Coulomb-ionization theories based on the plane-wave Born approximation, the binary-encounter approximation, and the simplified semiclassical approximation according to the Andersen, L/gsgaard, and Lund [Nucl. Instrum. Methods 192, 79 (1982)] and 1sσ molecular-orbital ionization theory. The calculations based on a perturbed-stationary-state approach including all the corrections such as the Coulomb deflection, the increased binding energy, and the relativistic effects, describe the data best although there are deviations in the case of Na at lower energies.

Hydrogen Balmer lines were observed in the plasma of a plane-cathode abnormal glow discharge in mixtures of argon or neon with hydrogen and in pure hydrogen. Intense spectral-line wing development was detected whenever argon was present in the plasma. This effect is related to the formation of ${\mathrm{H}}_2^{+}$ ions in a charge-transfer reaction between metastable ${\mathrm{Ar}}^{+}$ and ${\mathrm{H}}_2$ molecules.

A modification of resonance amplitudes is proposed that takes into account violent inner-shell processes accompanied by correlated multielectron transitions. For light ions with electrons in high Rydberg states, the conventional expression for the total widths of the resonance states given in terms of the Auger and radiative transition probabilities is not adequate. The present terms introduced to the widths can be very large and can seriously affect dielectronic recombination and resonance excitation; all the earlier calculations have been reexamined. Implications of this change on future calculations and on other related processes, such as photoionization plus Auger ionization, excitation-autoionization, multiple ionization, and similar processes in ion-atom collisions are also discussed.