The method of selective photoionization of individual subshells by monochromatized synchrotron radiation has been employed to measure all Coster-Kronig yields of the ${}_{54}{}^{}{}_{}{}^{}\mathrm{Xe}$ L subshells. The energy of the primary radiation was set at about 50 energy points in the range of the L edges. At each setting, the induced Xe L fluorescence and the induced Ar K fluorescence (used for normalization purposes) were recorded simultaneously by a Si(Li) detector. Both Xe and Ar were in the gaseous state. The recorded fluorescence spectra were carefully analyzed with proper modeling of the line tailing due to the intrinsic line profile and the detector line shape. The Coster-Kronig yields were derived by fitting the measured fluorescence intensities versus primary energy with the photoelectric cross sections. The derived yields are sensitive to the precise dependence of the cross sections on primary energy. Evaluations have been performed assuming a smooth power-law dependence and employing corrections for electron-correlation effects, which were estimated from comparative calculations in the independent-particle approximation and linear-response approximation models. Still, the uncertainties of the correlation effects constitute the main contribution to the uncertainties of the derived Coster-Kronig yields. The finally adopted values are ${\mathit{f}}_{12}$=0.12±0.03, ${\mathit{f}}_{13}$=0.23±0.04, and ${\mathit{f}}_{23}$=0.14±0.02.

Hierarchies of equations have been derived for the Legendre transform of the energy functionals of the density-functional theory. As an application, the Thomas-Fermi and the Thomas-Fermi-Dirac models are recovered and the Pauli energy is discussed. Useful relations for the electron density in the weighted-density and gradient approximations are derived.

The triplet nf Rydberg states of HD with n=9–17, L=3, v=1, and R=1,3 have been observed and identified with the laser–molecular-beam method. A 20-eV electron beam excites a collimated HD beam to the metastable 2p ${}_{}{}^3{}_{}{}^{}\mathrm{\Pi }$ state. Two counterpropagating cw single-frequency laser beams excite the metastable molecule first to the intermediate 3d ${}_{}{}^3{}_{}{}^{}\mathrm{\Pi }$ state, then to a triplet nf Rydberg state. The transition frequencies between the 3d and nf states have been measured to an accuracy of 0.02 ${\mathrm{cm}}^{\mathrm{-}1}$. The long-range model gives the transition frequencies to an accuracy of approximately 0.1 ${\mathrm{cm}}^{\mathrm{-}1}$. Using these energy-level measurements, the ionization potential of the metastable state has been determined to be 27 460.98(30) ${\mathrm{cm}}^{\mathrm{-}1}$ and the energy difference between the triplet metastable and the singlet ground state has been determined to be 97 105.50(30) ${\mathrm{cm}}^{\mathrm{-}1}$. In addition, the linewidths of the triplet Rydberg states have been measured, giving the autoionization rates.

The theory of optimal control of quantum systems is combined with a variational method for quantum-statistical dynamics to facilitate efficient nonperturbative calculations. The linear eigenfield approach is extended to the nonlinear regime to treat saturation and other higher-order effects. The application to a three-level Λ system generates, via an efficient iterative scheme, an eigenfield producing optimal constructive interference between direct and three-step excitation paths.

The 3${\mathrm{}}^3$${\mathit{S}}_1$–3${\mathrm{}}^3$${\mathit{P}}_{0,1,2}$ laser lines at 844.5 nm of atomic oxygen are studied in a weak discharge cell with argon buffer gas, using the optogalvanic effect. Three Doppler-limited peaks are observed at the center frequencies of the three fine-structure transitions. The measurements of the spectral widths indicate that the atoms in the lower state (3${\mathrm{}}^3$${\mathit{S}}_1$) are at room temperature or ‘‘cold.’’ This excludes the previous assumption that all the triplet states are very ‘‘hot’’ and moreover is consistent with the long-range atom-ion interaction model [Kwon et al., Phys. Rev. A 42, 4408 (1990); Bjerre and Keiding, Phys. Rev. Lett. 56, 1459 (1986)]. Based on the results, one can understand the unexplained observations such as the anomalously broadened spectra associated with the 3${\mathrm{}}^3$P triplet state, the peculiar four-peak emission spectra of the laser lines, and the absence of the J=0→J=1 transition.

The energies of 1${\mathit{s}}^2$2s2${\mathit{p}}^2$${\mathrm{}}^4$P and 1${\mathit{s}}^2$2${\mathit{p}}^3$${\mathrm{}}^4$${\mathit{S}}^{\mathit{o}}$ of the beryllium anion are calculated by the methods of full core plus correlation (FCPC) and restricted variation. The relativistic corrections are calculated with first-order perturbation theory. This is an application of FCPC to a five-electron atomic system. The energies obtained are much lower than previously expected. Combined with the most accurate theoretical and experimental data, the electron affinities of beryllium 1${\mathit{s}}^2$2s2p${\mathrm{}}^3$${\mathit{P}}^{\mathit{o}}$ and 1${\mathit{s}}^2$2${\mathit{p}}^2$${\mathrm{}}^3$P are predicted to be 289.1(10) and 295.0(7) meV, respectively. The former is considerably larger than the recent measurement of 261(10) meV. The transition wavelength of 1${\mathit{s}}^2$2s2${\mathit{p}}^2$${\mathrm{}}^4$P-1${\mathit{s}}^2$2${\mathit{p}}^3$${\mathrm{}}^4$${\mathit{S}}^{\mathit{o}}$ is predicted to be at 2653.70(68) Å, compared to the experimental observation at 2653.01(9) Å. The oscillator strength and the radiative lifetime are also calculated.

Probabilities and cross sections for ionization plus excitation in helium produced by fast heavy-particle impact have been evaluated. In these calculations, contributions from shake-off, time ordering, and independent interactions of the frozen-target electrons with the projectile are included. A comparison is made to recent experimental observations for the ratio of excitation-ionization to single-ionization total cross sections. A comparison is also made to calculations of excitation-ionization by fast electron impact.

Starting from a generalization of the Weisskopf-Wigner model for the case of a two-level atom with a largely spread center-of-mass wave function, we show that spatial correlations are destroyed to some extent by a spontaneously emitted photon. We derive a particularly simple form of the corresponding decoherence function and determine the dependence of the decoherence on orientation and size of a detector registering the outgoing photon.

The 4${\mathit{f}}^{14}$6s${\mathrm{}}^2$${\mathit{S}}_{1/2}$–4${\mathit{f}}^{14}$5d${\mathrm{}}^2$${\mathit{D}}_{5/2}$ 411-nm transition in ${}_{}{}^{172}{}_{}{}^{}\mathrm{Yb}_{}^{+}{}_{}{}^{}$ has been measured to be 729 476 868(11) MHz. The frequency was determined by probing a cold cloud of a few ${}_{}{}^{172}{}_{}{}^{}\mathrm{Yb}_{}^{+}{}_{}{}^{}$ ions held in a radio-frequency trap. The frequency measurement is part of a program to locate the 4${\mathit{f}}^{14}$6s${\mathrm{}}^2$${\mathit{S}}_{1/2}$–4${\mathit{f}}^{13}$6${\mathit{s}}^2$${\mathrm{}}^2$${\mathit{F}}_{7/2}$ 467-nm ultranarrow transition in laser-cooled ${\mathrm{Yb}}^{+}$. The 4${\mathit{f}}^{13}$6${\mathit{s}}^2$${\mathrm{}}^2$${\mathit{F}}_{7/2}$–4${\mathit{f}}^{13}$5d6s${\mathrm{}}^1$D[K= 5/2${]}_{\mathit{J}=5/2\mathrm{}}$ transition at 638 nm has been driven in order to depopulate the 4${\mathit{f}}^{13}$6${\mathit{s}}^2$${\mathrm{}}^2$${\mathit{F}}_{7/2}$ state.

We report the intensity dependence of photoassociative ionization collisions in a sodium magneto-optic trap (MOT). A suppressor beam with frequency tuned 600 MHz to the blue of the MOT trapping transition reduces the rate constant of the inelastic process by as much as a factor of 20 at an intensity of 8 W ${\mathrm{cm}}^{\mathrm{-}2}$. A comparison with theory shows good agreement.

We investigate direct, nonsequential ionization of argon atoms using linearly polarized laser light at 1053 nm with a 600-fs pulse length. We report the production of triply charged argon ions at intensities below the saturation intensity of the first charge state.

The motion of laser-cooled ${}_{}{}^{85}{}_{}{}^{}\mathrm{Rb}$ atoms along a one-dimensional optical potential under the influence of an external force is investigated. The transition from a region of low external force, where the motion is dominated by the optical potential, to one of a strong force, where the presence of the optical potential is hardly felt, is demonstrated. An unexpected discrepancy is found between the measured and expected value of the drift velocity induced by an applied magnetic field on a one-dimensional ${\mathrm{\sigma }}^{+}$-${\mathrm{\sigma }}^{\mathrm{-}}$ optical molasses.

We prove that the photon-number distribution of an arbitrary single-mode optical state can be calculated directly from the phase-averaged quadrature amplitude distribution, measured using optical homodyne detection. We experimentally demonstrate the application of this result by measuring the ultrafast (subpicosecond), time-resolved photon-number statistics of a weak field from a pulsed diode laser. Also presented is a numerical calculation of the photon-number distribution of a quadrature-squeezed vacuum state.

We discuss a requirement for the laser energy that is necessary to initiate electromagnetically induced transparency: The number of photons in the coupling laser pulse must exceed the product of the number of atoms in the laser path times the ratio of the oscillator strengths of the probe and coupling laser transitions.

Transparent closed forms of the radial ${\mathrm{SO}}_{\mathit{q}}$(N) Schrödinger equation acting on the noncommutative quantum Euclidean space are written both for l=0 and l≠0. Starting from the s-wave equation leads to the derivation of an alternative q analog of the radial Schrödinger equation in N space dimensions exhibiting a modified symmetry, now in terms of wave functions depending on the radial coordinate only. The harmonic oscillator and the Coulomb system are treated as concrete examples. These results open the way to the derivation of q-deformed (1/N)-energy formulas for arbitrary spherically symmetrical potentials. Comparisons with exact ${\mathrm{SO}}_{\mathit{q}}$(N) results, as well as further interpretations, have also been made.

It is found that in the semiclassical approximation, in situations with no turning point on the real axis, the reflection of a particle in a one-dimensional scattering potential U(z) occurs at the pairs of complex-conjugate reflecting points that include, at least, turning points and simple poles of the function U(z). No reflection at the double poles of the function U(z) has been found. The reflection coefficient may vanish only if there is more than one pair of reflecting points, due to the interference of the waves reflected partially at every pair. In the case of two pairs of complex-conjugate turning points, the equation that determines the energies of resonances is found to be the counterpart to the Bohr-Sommerfeld quantization rule that determines the energies of bound states when the turning points lie on the real axis.

A quasiclassical expression for the bound-free dipole moment in hydrogen is found to be in good agreement with the exact Gordon formula values. The approximation has the advantage of clearly indicating the dependence of the dipole moment on the initial- and final-state parameters. The quasiclassical expression is derived for small angular momentum states. The lowest-order angular momentum correction is required for good agreement in the visible frequency range. This correction term scales as ω(l+1${)}^3$ rather than ω(l+1/2${)}^3$ as might be expected for the Langer modification.

In the presence of a homogeneous magnetic field, the center of mass and electronic motion of an atom cannot be separated. For an atomic ion, the residual coupling is a Stark term with an oscillating electric field that is determined by the collective motion of the system. We investigate the effects and phenomena that occur due to this coupling in the classical dynamics of the highly excited ion. In particular, a permanent exchange of energy between the center of mass and the internal degrees of freedom is shown to take place. This leads, in the regular regime, in spite of an initially vanishing center-of-mass velocity, to the self-stabilization of the ion on a circular orbit. For small center-of-mass velocities and energies close to the ionization threshold, the motion of the atom is governed by its intermittent behavior. The most interesting dynamics occurs for rapidly moving ions for which the energy transfer from the center of mass to the internal degrees of freedom becomes strong enough to allow the atom to ionize. The statistics of this dynamical self-ionization process is studied for different center-of-mass velocities as well as internal energies.

The interactions of the ${\mathrm{Na}}^{+}$ ion and the Na atom with the ${\mathrm{C}}_{60}$ molecule are investigated within the formalism of unrestricted Hartree-Fock theory. Adsorption energies, structural parameters, and electronic energy levels are discussed for four and five sites inside the cage and outside the case, respectively. Possibilities of significant charge transfer from the adatom to the ${\mathrm{C}}_{60}$ molecule and subsequent decreases in the highest occupied molecular orbital–lowest unoccupied molecular orbital gaps are explored. Detailed comparisons with available experimental and theoretical data in the literature are presented.

We investigate classical and quantum one-dimensional models of two-electron atoms from the point of view of classical and quantum chaos. We propose a measure of electron-electron correlation as a quantum signature of classical chaos. The method is then applied to the three-dimensional multielectron wave functions of a Ca atom. The relation to quantum scars is stressed.