The dynamical image potential and ensuing forces induced by a charged particle moving parallel to a solid surface are investigated by using a dielectric formulation for semi-infinite dispersive media. The adiabatic behavior of the field in the asymptotic range is discussed in a general way using a multipole expansion. Several calculations illustrate the behavior of the field using both a simple model, where the surface response is approximated by a single plasma resonance, and a more realistic representation of the medium based upon the empirical information on the optical constants for various solids (Al, Cu, Ag, and Au). The model parameters may be adjusted to provide very good agreement with the optical-data integrations of the stopping and lateral forces on the moving charge. On the other hand, important differences in the description of the wake potential using either the simple plasma resonance model, or the optical-data representation, are obtained for Cu, Ag, and Au.

Charge-state distributions and energy losses of 0.67–1.5-MeV He ions scattered from a clean (100) surface of a SnTe single crystal are studied at glancing-angle incidence under UHV conditions. A stochastic model of charge exchange and energy loss of ions is developed, where inelastic interactions depend on the distance of the ion from the surface. Observed charge-state fractions and energy losses of the reflected He ions are explained with the model. Taking account of scattering of ions at surface steps, which causes the deflection of ion trajectories, position-dependent charge-exchange probabilities of He ions near the surface are derived from the observed charge-state distributions and charge-state dependence of the energy losses of scattered He ions.

A cesium sputter ion source is used to produce cluster beams of various materials. The size distributions of these clusters have been studied. The dependence of the cluster yields on the structure of the substrate used has also been studied for carbon.

In this work the calculation of the binding energy of three ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ atoms is carried out using δ-shell binary potential models, hyperspherical harmonic expansions, and adiabatic approximations. The results obtained with a one δ-shell potential are well within the range of those obtained by other workers using different techniques. The ones with the two δ-shell potentials are not. We show that attractive δ-shells lead to pathologies in calculations of the eigenpotentials, and in the resulting binding energies—and that those effects are expected to become more important for the two δ-shell binary potentials.

We examine the magnetic-moment distribution of ferromagnetic clusters under conditions where the magnetic moment is aligned with the internal cluster axis. Analytic expressions are obtained for the moment distribution and the adiabatic average moment induced in low fields. The result differs from the low-field Langevin function by a factor 2/3.

The mixing of Rydberg manifolds, induced by a ramped electric field F(t)=Ḟt, is modeled by interactions among two intersecting groups of parallel energy levels. The levels form a grid, each node of which is treated as an isolated two-level Landau-Zener anticrossing, characterized by probabilities D=exp(-2πγ) and A=1-D for diabatic and adiabatic transitions, respectively. The model assumes a core with one nonvanishing quantum defect ${\mathrm{\mu }}_0$ and with extremal Stark-level slopes, so that γ=‖${\mathrm{\mu }}_0$${\mathrm{\Vert }}^2$/3Ḟ${\mathit{n}}^{10}$ for all anticrossings, where the manifolds have principal quantum numbers n and n+1. Interference effects are ignored, which allows analytical treatment of the system’s evolution using path statistics or recursion relations. An initially populated edge state leads to a single-humped distribution of level populations. Analytical expressions are found for the probability distribution as a function of time, as well as its average and standard deviation. Limiting forms of the distribution at large times and in the diabatic (D→1) and adiabatic (D→0) limits are also given. These features are contrasted with those of a random walk. The relevance of the model to selective-field ionization is discussed.

We solve numerically the one-dimensional Schrödinger equation with a model potential for the case of excitation by two commensurate (the fundamental and third harmonic) intense laser fields and find a strong dependence of the atomic evolution and high-harmonic generation on the relative phase between the two fields. Our method employs the Kramers-Henneberger frame to exploit the insights gained from emphasizing the wave-packet dynamics of an electron oscillating under the influence of the strong laser fields.

We show that the concept of π pulses can be extended to multilevel systems. Generalized π pulses selectively excite a target state via a mechanism that is closely related to the familiar excitation dynamics in a two-level system. The corresponding generalized area theorem does not refer to the ‘‘area under the pulse envelope,’’ but to an integral over a difference of instantaneous quasienergies. Nevertheless, there are the same possibilities of pulse shaping for the generalized pulses as for their two-level counterparts. A semiclassical interpretation of the resonance condition leads to an analytical approximation to the relevant quasienergies, and shows that the excitation mechanism is universal.

We propose a quantum-nondemolition measurement of the amplitude quadrature and the photon-number statistics by using the effect of radiation pressure on a freely suspended mirror. We propose to measure the momentum fluctuations of the mirror which will give us a readout of the amplitude quadrature fluctuations. The scheme we propose is able to avoid the back-action noise leaving the state of the field after the measurement practically undegraded.

The connection between the main observables related to multiphoton ionization in a strong laser is analyzed through a very simple model. The interplay between ionization, the photoelectron spectrum, and harmonic generation is shown for different parameters of the field. The relation between individual harmonics and channel closing is analyzed. The Keldysh parameter gives infomation not only about the ionization regime, but also about the harmonic-generation efficiency.

An optical magnetometer based on atomic coherence effects is analyzed using a quantum Langevin approach. The large dispersion of a phase-coherent atomic medium (‘‘phaseonium’’) at a point of vanishing absorption is used to detect magnetic level shifts via optical phase measurements in a Mach-Zehnder interferometer with sensitivities potentially superior to state-of-the-art devices. Effects of Doppler broadening and fluctuations of the driving field are discussed and a comparison to standard optical-pumping magnetometers is made.

We have measured the absorption spectrum of a two-photon transition (3S to 5S in Na) for the case where the exciting laser has random telegraph frequency fluctuations. Good agreement was found between the experimental data and predictions for some features based on a theory due to Mollow [Phys. Rev. 175, 1555 (1968)]. Comparison is made with two-photon absorption spectra measured with a laser having Gaussian frequency fluctuations.

We study the dynamics of the driven Jaynes-Cummings model where an atom interacts with a single-mode cavity field but is also directly driven by an external radiation field. We show that the dynamic variables can be described in terms of ordinary Jaynes-Cummings dynamic variables with a different initial condition. We investigate the special case of an initial coherent state. We find collapses and revivals in the average number of photons at a much larger time scale than their Jaynes-Cummings model counterparts. We show that these ‘‘super-revivals’’ are related to the large-time-scale revivals that occur in the average electric field in the ordinary Jaynes-Cummings model. We also examine the photon statistics in the driven Jaynes-Cummings model and show that the cavity field is sub-Poissonian for certain interaction times.

We consider processes quadratic in incident intensity, in which two identical photons are annihilated simultaneously. We construct a formalism for these processes that is maximally analogous to the Stokes-Mueller formalism for linear processes. The two-photon properties of the incident beam require nine Stokes-like parameters for their description; the Mueller-like matrix which gives a complete description of frequency doubling or hyper-Raman scattering is of size 4×9. Of the 36 independent observable matrix elements, 12 are activated by pure real elastic dipole susceptibilities, four by an imaginary component in the electric dipole susceptibility (absorption), nine by handedness alone, two by extramultipole mechanisms alone, and nine require both handedness and extramultipole mechanisms.

In this paper we study the quantum Zeno effect in real space due to a position measurement. The motion of a particle is decelerated or comes to a complete stop when its position is observed. Instead of using the von Neumann collapse hypothesis, we treat a real measurement process. The measurement consists of coupling a two-level atom in a double-well potential to a resonant laser beam. Subsequent resonance fluorescence can be used to determine the atom’s position within the double well, provided the laser wavelength is short enough to ensure a resolvable scattering pattern of the fluorescence photons. Treating this process in the framework of dissipative quantum mechanics, we derive a master equation which describes the measurement process in all relevant details. Solving the master equation analytically as well as numerically we study the conditions for the decay of the nondiagonal elements. This leads directly to the inhibition of the center-of-mass motion, i.e., to a quantum Zeno effect. Because we treat the measurement process in detail we are able to investigate the conditions for a complete measurement. In particular, we study the role of the intensity and the wavelength of the probing laser field.

We study pattern formation in a degenerate optical parametric oscillator (OPO) by including diffractive effects due to the propagation in the optical cavity. The solution of zero amplitude for the OPO signal is found to be unstable to periodically modulated perturbations whenever the detuning parameter of the signal field is negative. A comparison between analytical solutions and numerical simulations for the roll structure shows excellent agreement for a wide range of input amplitudes. The threshold for the appearance of rolls is lower than the usual OPO threshold obtained in the plane-wave limit, especially for large detunings. When the input power is increased, roll patterns lose stability, leading to filamentation and optical turbulence.

We study the statistical properties of squeezed Kerr states generated by squeezing, with a two-photon parametric process, the output of a Kerr medium whose input is coherent light. The squeezing has the effect of allowing the photon statistics to depend on the Kerr nonlinearity. Without the squeezing the statistics are Poissonian, but after squeezing they may be either sub-Poissonian or super-Poissonian. We also study the Q-function quasiprobability distribution for these states and related distributions associated with the quantum-mechanical phase. Finally, we show that quadrature squeezing can be enhanced and that squeezing and sub-Poissonian statistics can coexist.

The correlations between two atoms in a generalized two-mode Jaynes-Cummings model (JCM), in the presence of a two-mode squeezed state, are studied. It is found that for a small amount of initial squeezing the correlations go back and forth between the radiation and the atoms. For large initial squeezing the atoms are found to be highly correlated at all times, while the squeezing of the radiation is destroyed as a function of time. In addition, the squeezing of the field is studied in the two-mode JCM and is compared to the one-mode squeezing that is obtained for the ordinary JCM. It is found that in the two-mode model the squeezing is preserved for longer times under the condition that ${\mathit{g}}_1$ and ${\mathit{g}}_2$ (the two coupling constants) are almost equal.

We discuss instabilities of the fundamental single-transverse-mode solution and the formation of new transverse spatial patterns in optical systems, containing nonlinearly absorbing two-level media using two transverse cavity geometries (rectangular and cylindrical). Under the appropriate approximations, these two models can be described by the same set of dynamical equations. Though the equations for the two models differ in their coefficients, their dynamical solutions are comparable. We find hysteresis phenomena associated with transitions in the transverse structure of the intensity which are completely different from the steady-state bistability and hysteresis found in theories of single-mode operation.

We present a list of nonlinear optics equations [the reduced Maxwell-Bloch system with pumping (or with a damping of a special type), nonlinear Schrödinger-Bloch equations with pumping, etc.] that can be solved by the inverse-scattering transform with a variable spectral parameter. We obtain the corresponding Lax pairs and equations for the spectral parameter.