The single-shot time-resolved laser-induced fluorescence (LIF) technique is well established for measuring radiative lifetimes of atomic states. On top of that, we show that the branching fraction of the pumped transition can be determined and hence also the absolute transition probability, provided that the LIF signal has been sufficiently saturated by the laser pulse. This additional information is solely deduced from the temporal nonlinear behavior of the LIF signal during laser pumping. The alternative procedure is based on the fact that atoms that decay spontaneously into the initial state can be re-excited during the same laser pulse, whereas atoms that decay into third levels cannot. First measurements of this kind have been performed on singly ionized iron. Lifetimes, branching fractions, and resulting transition probabilities are presented and compared with literature data.

Nuclear cusp conditions are obtained for the full electron-electron interaction energy density as well as for the exchange and correlation energy densities of density-functional theory. Their form is the same as the form of the well known Kato cusp condition for the electron-number density. All these cusp conditions are valid for both the ground and excited states of a molecule or solid.

Measurements of the absolute total cross section for single-electron capture in collisions of ${\mathrm{Cl}}^{7+}$ with ground-state atomic deuterium are reported in the energy range 4.6–428 eV/amu. These measurements represent the highest charge state yet reported using the Oak Ridge National Laboratory ion-atom merged-beams apparatus. The electron-capture cross section for ${\mathrm{Cl}}^{7+}$ is observed to decrease at lower energies, in contradiction to what is expected from a popular simple model and speculation from previous measurements for highly charged $\mathrm{}(7+)\mathrm{}$ ions with multielectron cores. The observed low-energy behavior is interpreted using coupled-channel molecular-orbital hidden-crossing calculations for ${\mathrm{N}}^{7+}+\mathrm{D}.$

Two ${\mathrm{CO}}_2$ lasers admitting quite different relaxation oscillation frequencies are coupled through a common saturable absorber. Despite their difference, these two lasers may successfully synchronize by exhibiting different oscillatory behaviors. The response of the low-frequency laser ${(L}_1)$ consists of strongly pulsating intensity oscillations while the large frequency laser ${(L}_2)$ exhibits bursting and nearly harmonic oscillations. These bursting oscillations are studied experimentally and numerically in terms of the pump parameter of $L_2.$ Above a critical point, the bursting oscillations are slowly decaying between successive pulses of $L_1$ but periodic synchronization between lasers remains possible. Below this critical point, the bursting oscillations are slowly expanding between pulses of $L_1$ and synchronization is no more periodic. These two distinct responses suggest a bifurcation phenomenon that we study analytically and numerically using a continuation method.

We consider pump-probe spectroscopy of a single ion with a highly metastable (probe) clock transition that is monitored by using the quantum jump technique. For a weak clock laser, we obtain the well-known Autler-Townes splitting. For stronger powers of the clock laser, we demonstrate the transition to a new regime. The two regimes are distinguished by the transition of two complex eigenvalues to purely imaginary ones, which can be very different in magnitude. The transition is controlled by the power of the clock laser. For pump on resonance, we present simple analytical expressions for various linewidths and line positions.

Wave-number blueshifts of single-mode laser light in low-density Rydberg matter are found to be due to stimulated Raman processes. The Rydberg matter is mainly formed from Rydberg states of K atoms. The lasers used are mW continuous-wave lasers in the ir, lead-salt tunable diode lasers. Of special significance is the blueshifting observed as shifts of Fabry-Perot etalon fringes of the order of 0.05 ${\mathrm{cm}}^{\mathrm{-}1}$. This blueshifting is explained as due to complete conversion to anti-Stokes radiation through higher-order stimulated Raman shifting by extremely small quanta from the near continuum of energy levels in the metallic Rydberg matter phase. Complicated strong shifts of intensity to larger wave numbers in the laser modes are also observed, due to coupling of laser side modes to the anti-Stokes waves. The high efficiency of the stimulated Raman process is partly due to the weak coupling to other degrees of freedom.

Based on nonperturbative numerical solutions of the Schrödinger equation it is demonstrated that a laser pulse with frequency tuned in resonance with a certain Rydberg level and the ground state of $\mathrm{H}\mathrm{}\left(1s\right)\mathrm{}$ generate a dynamical angular and radial electronic wave packet containing a large fraction of high-angular-momentum states. Only for sufficiently long laser pulses do the high-angular-momentum states appear and the excitation probability is then close to unity. The wave packet is predominantly built up of field-free eigenstates belonging to two principal n levels with a very different angular-momentum profile of each level. This induces a slow quasiperiodic fluctuation between a localized and delocalized electron density.

We have observed strongly modified spontaneous-emission spectra from laser dye in photonic crystals made of inverse opals in titania $\left({\mathrm{TiO}}_2\right).\mathrm{}$ We identify stop bands with large relative widths of $15\%,$ comparable to the dyes’ emission spectrum, and $75\%$ attenuation of the emission strength. For a wide range of angles, two stop bands are simultaneously manifested; their angle-dependent frequencies display an avoided crossing that is corroborated by reflectivity experiments. The edges of the stop bands agree well with band-structure calculations, but differ from simple Bragg diffraction as a result of multiple wave coupling. The strongly reduced dispersion of the Bloch modes likely causes a significant change in the density of states.

The Born-Oppenheimer adiabatic approximation is used to describe the dynamic realization of wave-function collapse in quantum measurement. In the adiabatic limit, it is shown that the wave function of the total system formed by the measured quantum system plus the measuring apparatus can be factorized as an entangled state with correlation between adiabatic quantum states and quasiclassical motion configurations of the large system. When the apparatus effectively behaves as a classical object, this adiabatic entanglement leads to the wave-function collapse, which creates an ideal quantum measurement process.

A detailed analysis of quantum key distribution employing entangled states is presented. We tested a system based on photon pairs entangled in energy-time optimized for long-distance transmission. It is based on a Franson-type setup for monitoring quantum correlations, and uses a protocol analogous to the Bennett-Brassard 1984 protocol. Passive-state preparation is implemented by polarization multiplexing in the interferometers. We distributed a sifted key of 0.4 Mbit at a raw rate of 134 Hz and with an error rate of 8.6% over a distance of 8.5 km. We thoroughly discuss the noise sources and practical difficulties associated with entangled-state systems. Finally, the level of security offered by this system is assessed and compared with that of faint-laser-pulse systems.

The recursion equation analysis of Grover’s quantum search algorithm presented by Biham et al. [Phys. Rev. A 60, 2742 (1999)] is generalized. It is applied to the large class of Grover-type algorithms in which the Hadamard transform is replaced by any other unitary transformation and the phase inversion is replaced by a rotation by an arbitrary angle. The time evolution of the amplitudes of the marked and unmarked states, for any initial complex amplitude distribution, is expressed using first-order linear difference equations. These equations are solved exactly. The solution provides the number of iterations T after which the probability of finding a marked state upon measurement is the highest, as well as the value of this probability, $P_{\max }.$ Both T and $P_{\max }$ are found to depend on the averages and variances of the initial amplitude distributions of the marked and unmarked states, but not on higher moments.

In the case of weak diatomic molecular predissociation by noninteracting, optically inactive continuum states, it is demonstrated that the predissociation line shape is more accurately represented by a Beutler-Fano profile than by a Lorentzian. The weak asymmetry that is found to occur is due principally to interactions with neighboring vibrational resonances. For this type of predissociation in the case of multiple continua, a sum rule for the corresponding line-shape asymmetry is derived. This sum rule is verified numerically using single-channel and multichannel coupled Schrödinger-equation calculations for the Schumann-Runge band system of ${\mathrm{O}}_2.$ Similar results are presented for the case of optically active continua.

In the framework of the Floquet formulation of time-dependent density functional theory we present several exact relations involving different parts of the quasienergy functional. These relations hold when the exact densities and exchange-correlation energy functional are employed. They can be used as useful constraints and tests when searching for the approximate forms of the time-dependent exchange-correlation functionals. The general results are illustrated on an exactly soluble model, Hooke’s atom in a linearly polarized monochromatic laser field.

The $L_3$ subshell x-ray intensity ratios for Hg, Bi, Th, and U have been measured using an annular source double reflection geometrical setup. Only the $L_3$ subshell of these elements were excited by the K x rays of the elements used as the primary targets. A Si(Li) detector connected to a Nuclear Data 66 B multichannel analyzer was used for counting. The experimental values were compared with theoretical values calculated using emission rates based on the Dirac-Hartree-Slater model and Dirac-Fock model.

Isotope shifts and hyperfine structures have been determined for the three near-ultraviolet transitions 405.8 nm ${(6s}^2{6p}^2{}^3{P}_2–{6s}^{2}6p7s{}^3{P}_1^o),$ 368.3 nm ${(6s}^2{6p}^2{}^3{P}_1–{6s}^{2}6p7s{}^3{P}_0^o),$ and 364.0 nm ${(6s}^2{6p}^2{}^3{P}_1–{6s}^{2}6p7s{}^3{P}_1^o)$ in stable isotopes of Pb I using the technique of saturated absorption spectroscopy in a sputtered vapor. The isotope shifts for these transitions and the magnetic hyperfine interaction constants for the ${6s}^2{6p}^2{}^3{P}_{1,2}$ metastable levels are the first Doppler-free determinations for these systems reported in the literature to our knowledge. Combined with experimental data, previously given in the literature, and pseudorelativistic Hartree-Fock estimates, the field shifts (FS’s) of seven relevant configurations are deduced: $\mathrm{FS}{(6s}^{2}6p7s)=2461\mathrm{MHz},$ $\mathrm{FS}{(6s}^{2}6p9p)=1838\mathrm{MHz},$ $\mathrm{FS}{(6s}^{2}6p6d)=1820\mathrm{MHz},$ $\mathrm{FS}{(6s}^{2}6p7d)=1668\mathrm{MHz},$ $\mathrm{FS}{(6s}^{2}6p8s)=2132\mathrm{MHz},$ $\mathrm{FS}{(6s}^{2}6p7p)=395\mathrm{MHz},$ and $\mathrm{FS}{(6s}^{2}6p5f)=-461\mathrm{MHz},$ referred to ${6s}^2{6p}^2.$ The hyperfine-structure integrals deduced from the experimental A factors for p electrons of the ground configuration ${6s}^2{6p}^2$ are in good agreement with results of ab initio calculations.

We have calculated the splitting between the $0_u^{-}$ and $1_u$ components of the $a{}^3{\Sigma }_u^{+}$ state of ${\mathrm{Rb}}_2$ and ${\mathrm{Cs}}_2$ using a relativistic ab initio configuration-interaction valence bond method. This so-called second-order spin-orbit splitting is entirely due to relativistic correlations within the molecule. Our ab initio nonperturbative splitting is 5 and 2 times larger than perturbative splittings at the inner turning point of the $a{}^3{\Sigma }_u^{+}$ potential for ${\mathrm{Rb}}_2$ and ${\mathrm{Cs}}_2,$ respectively. In addition, close-coupled nuclear dynamics calculations that estimate the effect of this splitting on experimentally accessible quantities are presented. The splitting affects the collisional loss rate of magnetically trapped ultracold Rb and Cs atoms and the spectroscopic determination of the vibrational structure of ${\mathrm{Rb}}_2$ and ${\mathrm{Cs}}_2$ dimers. Agreement with the experimental collisional loss rates of Cs is found.

We precisely calculate the fine and hyperfine structure splittings of the $\mathrm{}(v,J)=(1,35)\mathrm{}$ state in the antiprotonic helium atom, where $v$ is the vibrational quantum number and $J$ is the total orbital angular momentum. The coupled rearrangement channel method is employed to efficiently describe correlation effects in the three-body system with atomic and molecular characters. An accuracy of better than ${\alpha }^2\approx 50\mathrm{ppm}$ has been achieved. The result obtained is in good agreement with the previous calculation within $\sim 200\hspace{0.5em}\mathrm{ppm}.$ We also examine the correlation effects, in particular orbital polarization effects.

An improved version of the recently developed non-Markovian energy corrected sudden (ECS) model [J. V. Buldyreva and L. Bonamy, Phys. Rev. A 60, 370 (1999)] is proposed to ensure good accuracy of the quasiexponential behavior of the scattered light intensity vs frequency that is observed experimentally in the far wings of nitrogen spectra. To this end, the more refined translational spectrum proposed by Birnbaum and Cohen [Can. J. Phys. 54, 593 (1976)] is used as the adiabaticity factor. At low frequencies it reduces to the traditional one-parameter Lorentzian shape which describes the long-time translational dynamics and allows the basic ECS transition rates to be identified. At high frequencies it introduces an additional parameter which describes the short-time dynamics. The value of this parameter at room temperature and at low temperature (150 K) is obtained by fitting the far-wing theoretical intensities of the depolarized nitrogen spectra to their experimental values. This value compares favorably with its theoretical evaluation.

The $3d$ photoelectron spectrum of xenon has been measured at several photon energies in the immediate threshold region. The absolute photoionization cross section and angular anisotropy parameter β have been determined for the two spin-orbit-split components. The experimental results are compared with calculations using a relaxed single-channel approximation. In agreement with theory, most abrupt changes in cross section and angular distribution are observed just above threshold. However, the Xe ${3d}_{5/2}$ photoionization cross section also reveals, some 30-eV above threshold a second maximum that has not been predicted theoretically.

The stopping power for the case of incident electrons is considered. We use our recently developed extension of Bethe’s theory, which deals specifically with the binding of the electrons within the target atoms in the contributions from electron exchange. Shell corrections, which account for certain approximations used in the original presentation of this theory, are obtained. Our results expand the reach of Bethe’s description of the stopping power to a regime of lower incident velocities. They indicate that there can be significant corrections arising from the treatment of the binding energy in the exchange contributions to the stopping power.