Results of the most sophisticated measurements in coincidence with the angular-resolved $K$-shell photoelectrons and Auger electrons and with two atomic ions produced by dissociation of ${\mathrm{N}}_2$ molecule are analyzed. Detection of photoelectrons at certain angles makes it possible to separate the Auger decay processes of the $1{\sigma }_g$ and $1{\sigma }_u$ core-hole states. The Auger electron angular distributions for each of these hole states are measured as a function of the kinetic-energy release of two atomic ions and are compared with the corresponding theoretical angular distributions. From that comparison one can disentangle the contributions of different repulsive doubly charged molecular ion states to the Auger decay. Different kinetic-energy-release values are directly related to the different internuclear distances. In this way one can trace experimentally the behavior of the potential energy curves of dicationic final states inside the Frank-Condon region. Presentation of the Auger-electron angular distributions as a function of kinetic-energy release of two atomic ions opens a new dimension in the study of Auger decay.

A thermal atomic beam of dysprosium atoms is cooled using the $4f^{10}6s^2(J=8)\to 4f^{10}6s6p(J=9)$ transition at $421$ nm. The cooling is done via a standing light wave orthogonal to the atomic beam. Efficient transverse cooling to the Doppler limit is demonstrated for all observable isotopes of dysprosium. Branching ratios to metastable states are demonstrated to be $<$$5\times {10}^{-4}$. A scheme for enhancement of the nonzero-nuclear-spin-isotope cooling and a method for direct identification of possible trap states are proposed.

The coupled motion of ions in a radiofrequency trap has been used to connect the frequency-dependent laser-induced heating of a sympathetically cooled spectroscopy ion with changes in the fluorescence of a laser-cooled control ion. This technique, sympathetic heating spectroscopy, is demonstrated using two isotopes of calcium. In the experiment, a few scattered photons from the spectroscopy ion are transformed into a large deviation from the steady-state fluorescence of the control ion. This allows us to detect an optical transition where the number of scattered photons is below our fluorescence detection limit. Possible applications of the technique to molecular ion spectroscopy are briefly discussed.

We investigate the infrared (IR)-laser-assisted photoionization of He by a coherent extreme ultraviolet (euv) light solving the time-dependent Schrödinger equation. A combined field of the 13th and 15th harmonics created from the same IR laser source is used to ionize He atoms coherently. We show that the ionization probabilities oscillate as a function of the time delay between the IR and the euv pulses. On the other hand, the oscillation amplitude increases as the IR intensity increases, reaches a maximum when the IR intensity is around $6\times {10}^{12}\hspace{0.5em}\mathrm{W}/{\mathrm{cm}}^2$, and then decreases as the IR intensity increases further. Decomposing the ionization probabilities by the 13th and 15th harmonics, we illustrate that the oscillation amplitude is small for a lower IR laser intensity due to the fact that the transition strength by the 13th harmonic is much smaller than the one by the 15th harmonic. When the IR intensity increases further above $6\times {10}^{12}\hspace{0.5em}\mathrm{W}/{\mathrm{cm}}^2$, the transition strength by the 13th harmonic becomes larger than the one by the 15th harmonic and the oscillation amplitude is reduced again. By tuning the relative field strengths of the 13th and 15th harmonics or the IR intensity, we can control the oscillation amplitude.

By numerical simulation of the time-dependent Gross-Pitaevskii equation we show that a weakly interacting or noninteracting Bose-Einstein condensate (BEC) vortex can be localized in a three-dimensional bichromatic quasiperiodic optical-lattice (OL) potential generated by the superposition of two standing-wave polarized laser beams with incommensurate wavelengths. We also study the localization of a (nonrotating) BEC in two and three dimensions by bichromatic OL potentials along orthogonal directions. This is a generalization of the localization of a BEC in a one-dimensional bichromatic OL as studied in a recent experiment [Roati et al., Nature 453, 895 (2008)]. We demonstrate the stability of the localized state by considering its time evolution in the form of a stable breathing oscillation in a slightly altered potential for a large period of time. Finally, we consider the localization of a BEC in a random one-dimensional potential in the form of several identical repulsive spikes arbitrarily distributed in space.

We present the essential experimental steps of our all-optical approach to prepare a double-degenerate Fermi-Fermi mixture of ${}^6\mathrm{Li}$ and ${}^{40}\mathrm{K}$ atoms, which then serves as a starting point for molecule formation. We first describe the optimized trap loading procedures, the internal-state preparation of the sample, and the combined evaporative and sympathetic cooling process. We then discuss the preparation of the sample near an interspecies Feshbach resonance, and we demonstrate the formation of heteronuclear molecules by a magnetic field ramp across the resonance.

We study the output coupling of atoms from a magnetic trap into a linear potential slope of gravity using a weak radio-frequency field. We present a one-dimensional wave-packet model based on a continuous loading of a continuous spectrum of generalized eigenstates to describe the scenario. Analyzing the model, we show how the interference of the classical coupling fields maps to the interference of the resulting atomic streams.

A Bose-Einstein condensate of ultracold atoms inside the field of a laser-driven optical cavity exhibits dispersive optical bistability. We describe this system by using mean-field approximation and by analyzing the correlation functions of the linearized quantum fluctuations around the mean-field solution. The entanglement and the statistics of the atom-field quadratures are given in the stationary state. It is shown that the mean-field solution, that is, the Bose-Einstein condensate, is robust against entanglement generation for most of the phase diagram.

Adiabatic techniques using multilevel systems have recently been generalized from the optical case to settings in atom optics, solid state physics, and even classical electrodynamics. The most well known example of these is the so-called stimulated Raman adiabatic passage (STIRAP) process, which allows transfer of a particle between different states with large fidelity. Here we generalize and examine this process for an atomic center-of-mass state with a nontrivial phase distribution and show that even though dark state dynamics can be achieved for the atomic density, the phase dynamics will still have to be considered as a dynamical process. In particular we show that the combination of adiabatic and nonadiabatic behavior can be used to engineer phase superposition states.

We report measurements of absolute transition frequencies and hyperfine coupling constants for the $8S_{1/2}$, $9S_{1/2}$, $7D_{3/2}$, and $7D_{5/2}$ states in ${}^{133}\mathrm{Cs}$ vapor. The stepwise excitation through either the $6P_{1/2}$ or $6P_{3/2}$ intermediate state is performed directly with broadband laser light from a stabilized femtosecond laser optical-frequency comb. The laser beam is split, counterpropagated, and focused into a room-temperature Cs vapor cell. The repetition rate of the frequency comb is scanned and we detect the fluorescence on the $7P_{1/2,3/2}\to 6S_{1/2}$ branches of the decay of the excited states. The excitations to the different states are isolated by the introduction of narrow-bandwidth interference filters in the laser beam paths. Using a nonlinear least-squares method we find measurements of transition frequencies and hyperfine coupling constants that are in agreement with other recent measurements for the $8S$ state and provide improvement by $2$ orders of magnitude over previously published results for the $9S$ and $7D$ states.

Generation of low-order harmonics (third and fifth) of the fundamental radiation of a $Q$-switched Nd:YAG laser ($1064$ nm, pulse $15$ ns) was observed in a CaF${}_2$ laser ablation plume. The ablation process is triggered by a second $Q$-switched Nd:YAG laser operating at $532$ or $266$ nm. In the scheme employed, the fundamental laser beam propagates parallel to the target surface at controllable distance and temporal delay, allowing to the probing of different regions of the freely expanding plume. The intensity of the harmonics is shown to decrease rapidly as the distance to the target is increased, and for each distance, an optimum time delay between the ablating laser pulse and the fundamental beam is found. In situ diagnosis of the plume by optical emission spectroscopy and laser-induced fluorescence serves to correlate the observed harmonic behavior with the temporally and spatially resolved composition and velocity of flight of species in the plume. It is concluded that harmonics are selectively generated by CaF species through a two-photon resonantly enhanced sum-mixing process exploiting the ($B$ ${}^2{\Sigma }^{+}–X$ ${}^2{\Sigma }^{+}$, $\Delta \nu =0$) transition of the molecule in the region of 530 nm. In this work polar molecules have been shown to be the dominating species for harmonic generation in an ablation plume. Implications of these results for the generation of high harmonics in strongly polar molecules which can be aligned in the ablation plasma are discussed.

We analyze both theoretically and by means of numerical simulations the phenomena of filamentation and dynamical formation of self-guided nonlinear waves in media featuring competing cubic and quintic nonlinearities. We provide a theoretical description of recent experiments in terms of a linear stability analysis supported with simulations, showing the possibility of the observation of modulational instability suppression of intense light pulses traveling across such nonlinear media. We also show a mechanism of indirect excitation of light condensates by means of coalescence processes of nonlinear coherent structures produced by managed filamentation of high-power laser beams.

We examine the behavior of a non-Gaussian state like the maximally path-entangled number state commonly known as a $N00N$ state under phase-insensitive amplification. We derive an analytical result for the density matrix of the $N00N$ state for arbitrary gain of the amplifier. We consider cases of both symmetric and antisymmetric amplification of the two modes of the $N00N$ state. We quantitatively evaluate the loss of entanglement by the amplifier in terms of the logarithmic negativity parameter. We find that $N00N$ states are more robust than their Gaussian counterparts.

The optical absorption spectra of sodium clusters (Na${}_{2n}$, $n⩽$ $4$) are calculated by using an all-electron first-principles $\mathit{GW}+$Bethe-Salpeter method with the mixed-basis approach within the Tamm-Dancoff approximation. In these small systems, the excitonic effect strongly affects the optical properties due to the confinement of exciton in the small system size. The present state-of-the-art method treats the electron-hole two-particle Green’s function by incorporating the ladder diagrams up to the infinite order and therefore takes into account the excitonic effect in a good approximation. We check the accuracy of the present method by comparing the resulting spectra with experiments. In addition, the effect of delocalization in particular in the lowest unoccupied molecular orbital in the $\mathit{GW}$ quasiparticle wave function is also discussed by rediagonalizing the Dyson equation.

We consider a mixture of two bosonic species with tunable interspecies interaction in a periodic potential and discuss the advantages of low filling factors on the detection of the pair-superfluid phase. We show how the emergence of such a phase can be put dramatically into evidence by looking at the interference pictures and density correlations after expansion and by changing the interspecies interaction from attractive to repulsive.

A generalized Ginzburg-Landau equation describing dissipative solitons dynamics in negative-refractive-index materials is derived from Maxwell equations. This equation having only real terms with opposite sign differs from the usual Ginzburg-Landau equation for positive-refractive-index media. A cross-compensation between the saturating nonlinearity excess, losses, and gain makes obtained self-organized solitons dissipationless and exceptionally robust. In the presence of such solitons medium becomes effectively dissipationless. The compensation of losses is of particular interest for media with resonant character of interactions like negative-refractive-index materials.

The sulfur electron affinities ${}^{e}A$(S) are measured by photodetachment microscopy for the two isotopes ${}^{32}\mathrm{S}$ and ${}^{34}\mathrm{S}$ ($16$ $752.975$ 3(41) and $16$ $752.977$ 6(85) cm${}^{-1}$, respectively). The isotope shift in the electron affinity is found to be more probably positive, ${}^{e}A$(${}^{34}\mathrm{S}$)$-\hspace{0.5em}{}^{e}A$(${}^{32}\mathrm{S}$) $=+0.0023(70)$ cm${}^{-1}$, but the uncertainty allows for the possibility that it may be either “normal” [${}^{e}A$(${}^{34}\mathrm{S}$) $>\hspace{0.5em}{}^{e}A$(${}^{32}\mathrm{S}$)] or “anomalous” [${}^{e}A$(${}^{34}\mathrm{S}$) $<\hspace{0.5em}{}^{e}A$(${}^{32}\mathrm{S}$)]. The isotope shift is estimated theoretically using elaborate correlation models, monitoring the electron affinity and the mass polarization term expectation value. The theoretical analysis predicts a very large specific mass shift (SMS) that counterbalances the normal mass shift (NMS) and produces an anomalous isotope shift ${}^{e}A$(${}^{34}\mathrm{S}$)$-\hspace{0.5em}{}^{e}A$(${}^{32}\mathrm{S}$) $=-0.0053(24)$ cm${}^{-1}$, field shift corrections included. The total isotope shift can always be written as the sum of the NMS (here $+0.0169$ cm${}^{-1}$) and a residual isotope shift (RIS). Since the NMS has nearly no uncertainty, the comparison between experimental and theoretical RIS is more fair. With respective values of $-0.0146(70)$ cm${}^{-1}$ and $-0.0222(24)$ cm${}^{-1}$, these residual isotope shifts are found to agree within the estimated uncertainties.

In standard computations in theoretical quantum chemistry the accepted values of the fundamental physical constants are assumed. Alternatively, the tools of computational quantum chemistry can be used to investigate hypothetical chemistry that would result from different values of these constants, given the same physical laws. In this work, the dependence of a variety of basic chemical quantities on the values of the fine-structure constant and the electron-proton mass ratio is explored. In chemistry, the accepted values of both constants may be considered small, in the sense that their increase must be substantial to seriously impact bond energies. It is found that if the fine-structure constant were larger, covalent bonds between light atoms would be weaker, and the dipole moment and hydrogen-bonding ability of water would be reduced. Conversely, an increase in the value of the electron-proton mass ratio increases dissociation energies in molecules such as ${\mathrm{H}}_2$, ${\mathrm{O}}_2$, and CO${}_2$. Specifically, a sevenfold increase in the fine-structure constant decreases the strength of the O–H bond in the water molecule by 7 kcal mol${}^{-1}$ while reducing its dipole moment by at least $10\%$, whereas a 100-fold increase in the electron-proton mass ratio increases the same bond energy by 11 kcal mol${}^{-1}$.

We use the zero-range approximation to study a system of two identical bosons interacting resonantly with a third particle. The method is derived from effective field theory. It reduces the three-body problem to an integral equation which we then solve numerically. We also develop an alternative approach which gives analytic solutions of the integral equation in coordinate representation in the limit of vanishing total energy. The atom-dimer scattering length, the rates of atom-dimer relaxation, and the three-body recombination to shallow and to deep molecular states are calculated either analytically or numerically with a well-controlled accuracy for various energies as functions of the mass ratio, scattering length, and three-body parameter. We discuss in detail the relative positions of the recombination loss peaks, which in the universal limit depend only on the mass ratio. Our results have implications for ongoing and future experiments on Bose-Bose and Bose-Fermi atomic mixtures.

Femtosecond time-resolved velocity map imaging combined with multiphoton ionization was applied to study the optical field modulation of NO Rydberg-state populations. The $A\hspace{0.5em}{}^2{\Sigma }^{+}$($\upsilon =2$) state is populated by absorption of one $271$-nm photon. Two peaks in the photoelectron kinetic energy spectra, centered at $0.82$ and $2.35$ eV, are caused by ionization from the $A\hspace{0.5em}{}^2{\Sigma }^{+}$($\upsilon =2$) state by time-delayed one-color and two-color multiphoton ionization, respectively. In the overlap region of the pump and probe light, the $C\hspace{0.5em}{}^2\Pi$($\upsilon =4$) state is populated by a $1+1^{\prime }$ excitation. When the pump laser intensity is increased, other Rydberg states ($E\hspace{0.5em}{}^2{\Sigma }^{+}$, $F\hspace{0.5em}{}^2\Delta$, and $D\hspace{0.5em}{}^2{\Sigma }^{+}$) are moved into resonance by a laser-induced Stark shift. These states can be populated only within the temporal overlap region of the pump and probe light. When the intensity of the pump laser is higher than $2.9$ $\times$ ${10}^{12}$ W/cm${}^2$, Rydberg-valence coupling between the $A\hspace{0.5em}{}^2{\Sigma }^{+}$($\upsilon =2$) and $B\hspace{0.5em}{}^2\Pi$($\upsilon =4$) states may play a key role, resulting in photoelectrons with kinetic energy of $0.37$ eV. The coupling strength increases with increasing pump laser intensity.