Optically pumped Na is used as a spin-exchange partner to polarize ${}^3\mathrm{He}.$ Polarizations around 20% have routinely been achieved in sealed spherical glass cells containing ${}^3\mathrm{He},$ ${\mathrm{N}}_2,$ and a few droplets of Na. An optical technique has been developed to determine the $\mathrm{Na}{-}^3\mathrm{He}$ spin-exchange rate coefficient. By monitoring the Na spin relaxation “in the dark,” the average Na-Na spin-destruction cross section at $330°\mathrm{C}$ is estimated to be around $5\times {10}^{-19}{\mathrm{cm}}^2.$ This value is 2–5 (15–30) times smaller than the previously reported values for the K-K (Rb-Rb) spin-relaxation cross section. In the temperature range $310–355°\mathrm{C}$ the spin-exchange rate coefficient is found to be $(6.1\mathrm{}\pm 0.6)\times {10}^{-20}{\mathrm{cm}}^3/\mathrm{s}$ with no detectable temperature dependence. This value is in good agreement with a previous theoretical estimate reported by Walker and it is only slightly lower than the corresponding $\mathrm{Rb}{-}^3\mathrm{He}$ spin-exchange rate coefficient. The total $\mathrm{Na}{-}^3\mathrm{He}$ spin-destruction rate coefficient is, within errors, found to be the same as the $\mathrm{Na}{-}^3\mathrm{He}$ spin-exchange rate coefficient, thereby indicating that the maximum possible photon efficiency may approach unity for the $\mathrm{Na}{-}^3\mathrm{He}$ system. A technique, in which a charge-coupled device camera is used to take images of faint unquenched fluorescence light, has been utilized to allow for an instantaneous determination of the sodium number densities during the rate coefficient measurements.

The effect of laser fields on the NO interaction potentials is obtained by the calculation of time-resolved photoelectron spectrum (TRPES) using the time-dependent wave-packet method. The calculation not only shows that the overlap of the pump-probe pulses makes some NO molecular “invisible” states visible, but also that the coupling strength and the positions of relevant curves change on increasing the laser intensity. These changed potentials affect their dynamical behavior and influence the shape and position of each peak in TRPES. That the coupling strength of relevant potentials can be changed by the field-matter interaction is consistent with our ab initio calculations.

The dynamics of an electron wave packet in the presence of laser radiation and of a one-dimensional repulsive soft-core potential is investigated. For different laser intensities and for different initial positions of the electron wave packet, these results are compared with those for an attractive potential. The repulsive potential is capable of confining the electron quite efficiently under appropriate conditions. In these conditions, the electron is shown to emit a high harmonic spectrum similar to that emitted by the more conventional attractive potential. It is thus argued that recombination into an atomic bound state as required by the three step model is not essential for the emission of high harmonics.

We analyze recent experiments at JILA, which observe periodic formation of stripes in a rotating Bose condensate [Engels et al., Phys. Rev. Lett. 89, 100403 (2002)], and explain this behavior as a consequence of kinetic energy driven evolution, where the vortices follow a quadrupolar flow. We demonstrate that the structure of vortex lattices in the lowest Landau level is a useful tool for understanding such complex phenomena, even when the system is not in the quantum Hall regime.

We propose a feasible experiment to investigate quantum effects in geometric phases, arising when a classical source drives not a single quantum system, but two interacting ones. In particular, we show how to observe a signature of the quantization of the electromagnetic field through a vacuum effect in Berry’s phase. To do so, we describe the interaction of an atom and a quantized cavity mode altogether driven by an external quasiclassical field. We also analyze the semiclassical limit recovering the usual Berry’s phase results.

The equations of motion for the molecular rotation are derived for vibrationally cold dimers that are polarized by off-resonant laser light. It is shown that, by eliminating electronic and vibrational degrees of freedom, a quantum master equation for the reduced rotational density operator can be obtained. The coherent rotational dynamics is caused by stimulated Raman transitions, whereas spontaneous Raman transitions lead to decoherence in the motion of the quantized angular momentum. As an example the molecular dynamics for the optical Kerr effect is chosen, revealing decoherence and heating of the molecular rotation.

In the present paper, we perform a systematic calculation of the complex resonance energy for metastable states in the antiprotonic helium atoms, which decay predominantly via Auger transitions, by using the complex-coordinate rotation (CCR) method. Special attention is paid to relativistic corrections for the bound electron related to the Breit interaction. These corrections have been calculated using the CCR wave functions, which are square integrable. Some higher-order relativistic and QED effects have been included into consideration to get precise theoretical values for transition frequencies.

The fine-structure intervals in the $n=29\mathrm{}$ state of ${\mathrm{Si}}^{2+}$ separating levels from $L=8\mathrm{}$ to $L=14\mathrm{}$ have been measured by microwave spectroscopy. A beam of ${\mathrm{Si}}^{3+}$ (Na-like silicon) captures a single electron from an $n=10\mathrm{}$ Rydberg target, forming highly excited Rydberg states of ${\mathrm{Si}}^{2+}$ near $n=29.\mathrm{}$ Specific L levels within $n=29\mathrm{}$ are selectively detected by excitation with a Doppler-tuned ${\mathrm{CO}}_2$ laser, followed by Stark ionization. This allows the detection of microwave induced transitions between different L levels in the $n=29\mathrm{}$ state, determining the fine-structure intervals. The fine-structure pattern can be used to deduce the dipole polarizability of the ${\mathrm{Si}}^{3+}$ ion, which forms the core of the Rydberg system. The result ${\alpha }_d=7.404\mathrm{}\left(11\right)\mathrm{}$ is in good agreement with calculations that are comparable in precision.

A model based on atomic ionization of ${\mathrm{F}}^{-}$ sites at the surface is used to calculate the surface track potential created by fast protons at LiF surfaces. For 100-keV protons at grazing incidence, we find that the track potential close to the surface plays a significant role in determining the shift to lower energies of the convoy electron peak with respect to the unperturbed cusp value.

We demonstrate that strong transient phase-space localization can be achieved by the application of a single impulsive “kick” in the form of a short (600 ps) unidirectional electric-field pulse to a strongly polarized, quasi-one-dimensional Rydberg atom. The underlying classical dynamics is analyzed and it is shown that phase-space localization results from a focusing effect analogous to rainbow scattering. Moreover, it is shown that the essential features of the classical analysis remain valid in a quantum-mechanical treatment of the system in terms of its phase-space Husimi distribution. The degree of phase-space localization is characterized by the coarse-grained Renyi entropy. Transient phase-space localization is demonstrated experimentally using extreme redshifted $m=0\mathrm{}$ potassium Stark states in the $n=351\mathrm{}$ manifold and a short probe pulse. The experimental data are in good agreement with theoretical predictions. The localized state provides an excellent starting point for further control and manipulation of the electron wave packet.

The energy-band structure and energy splitting due to quantum tunneling in two weakly linked Bose-Einstein condensates were calculated by using the instanton method. The intrinsic coherent properties of Bose-Josephson junction (BJJ) were investigated in terms of energy splitting. For $E_C{/E}_J\ll 1,$ the energy splitting is small and the system is globally phase coherent. In the opposite limit, $E_C{/E}_J\gg 1,$ the energy splitting is large and the system becomes phase dissipated. Our results suggest that one should investigate the coherence phenomena of BJJ in proper condition such as $E_C{/E}_J\sim 1.$

We show that in the presence of finite catalysts, any pure bipartite entangled state can be converted into any other, to unlimited accuracy, without the use of any communication, quantum or classical. We call this process embezzling entanglement because it involves removing a small amount of entanglement from the catalyst in a physically unnoticeable way.

Double ionization by a single photon is often discussed in terms of two mechanisms, namely, shakeoff and knockout, dominant at high and low photon energies, respectively. We have developed a model to formulate the explicit but separate contribution of both mechanisms at all energies [Phys. Rev. Lett. 89, 073002 (2002)]. The separation is based on a quasiclassical formulation of knockout which is free from any shakeoff part since the latter is purely quantum mechanical. The relevance of each mechanism from threshold up to several keV photon energy is quantified and discussed in detail for the photoionization from the ground state of two-electron atoms. Photoionization ratios, integral and singly differential cross sections calculated for helium and other members of its isoelectronic sequence are compared to benchmark experimental data and recent theoretical results. A connection to Samson’s half-collision model [Phys. Rev. Lett. 65, 2861 (1990)] is also given.

We calculate magneto-optical rotation of nonmonochromatic fields in an optically thick cold atomic medium. We show that the nonmonochromatic nature leads to a nonlinear dependence of the rotation angle on optical density. Using our calculations, we provide a quantitative analysis of the recent experimental results of Labeyrie et al. [Phys. Rev. A 64, 033402 (2001)] using cold ${}^{85}\mathrm{Rb}$ atoms.

The correspondence between classical and quantum invariants is established. The Ermakov-Lewis quantum invariant of the time-dependent harmonic oscillator is translated from the coordinate and momentum operators into amplitude and phase operators. In doing so, Turski’s phase operator as well as Susskind-Glogower operators are generalized to the time-dependent harmonic-oscillator case. A quantum derivation of the Manley-Rowe relations is shown as an example.

The fully adiabatic ${}^{\infty }{\mathrm{H}}_2^{+}$ ion is considered by using the improved version of our multibox variational procedure [A.M. Frolov, Phys. Rev. E 64, 036704 (2001)]. This procedure has been developed and successfully tested in highly accurate computations of bound-state spectra of various three-body systems. Note that our method is not based on the Born-Oppenheimer approximation, i.e., it is a nonadiabatic approach. In this study, we determine the ground-state energies of the adiabatic ${\mathrm{HD}}^{+},$ ${\mathrm{HT}}^{+},$ and ${\mathrm{T}}_2^{+}$ ions with finite nuclear masses. The computed variational energies for the ${\mathrm{HD}}^{+},$ ${\mathrm{HT}}^{+},$ and ${\mathrm{T}}_2^{+}$ ions are $-0.597897968645036508\mathrm{a}.\mathrm{u}.\mathrm{},$ $-0.598176134669766232\mathrm{a}.\mathrm{u}.\mathrm{},$ and $-0.59950691011154145113\mathrm{a}.\mathrm{u}.\mathrm{},$ respectively. The ground-state energy and bound-state properties of ${}^{\infty }{\mathrm{H}}_2^{+}$ ion are also presented. In general, the observed agreement between our variational energies and analogous energies determined with the use of pure adiabatic methods can be considered as very good.

In a recent paper, Dürr [Phys. Rev. A 64, 042113 (2001)] proposed an interesting multibeam generalization of the quantitative formulation of interferometric wave-particle duality, discovered by Englert for two-beam interferometers. The proposed generalization is an inequality that relates a generalized measure of the fringe visibility to certain measures of the maximum amount of which-way knowledge that can be stored in a which-way detector. We construct an explicit example where, with three beams in a pure state, the scheme proposed by Dürr leads to the possibility of an ideal which-way detector that can achieve a better path discrimination at the same time as a better fringe visibility. In our opinion, this seems to be in contrast with the intuitive idea of complementarity, as it is implemented in the two-beams case, where an increase in path discrimination always implies a decrease of fringe visibility, if the beams and the detector are in pure states.

We consider ionization of atomic hydrogen with emission of low-energy electrons by proton and antiproton impact in the range of impact velocities $3\mathrm{a}.\mathrm{u}.\mathrm{}<~v_p<~6\mathrm{a}.\mathrm{u}.\mathrm{},$ where the electron capture by protons is already of minor importance but the differences in hydrogen ionization due to proton and antiproton impact can still be substantial. By calculating various differential cross sections within the first and second Born and continuum-distorted-wave–eikonal-initial-state (CDW-EIS) approximations we attempt to analyze the dynamics of hydrogen ionization by protons and antiprotons. We discuss in some detail the role of (i) the interaction between the projectile and the target nucleus and (ii) multiphoton exchanges between the projectile and the target electron. Profound charge-sign effects are suggested by CDW-EIS and second Born calculations for the fully differential emission pattern. Although after the integration over the electron emission angles these effects substantially diminish, they still remain noticeable even in the total ionization cross section suggesting, in particular, that protons are more effective, compared to antiprotons, in producing soft electron emission from hydrogen in the range of collision velocities under consideration.

First-principles studies of the geometry and energetics of the ${\mathrm{Si}}_{36}$ cluster are performed by searching 17 structural isomers including cage, wire, and stuffed fullerene. It is found that the tricapped-trigonal-prism unit is not the structural unit for ${\mathrm{Si}}_{36},$ and the stable structure is identified to have a more spherical geometry derived from the stuffed fullerene configurations. This is in agreement with the experiment which suggested a structural transition from the elongated geometry to a more spherical one for the medium sized silicon cluster [Hudgins et al., J. Chem. Phys. 111, 7865 (1999); Bergeron et al., J. Chem. Phys. 117, 3219 (2002)].