We present the first theoretical treatment that accounts in detail for a recent observation of overlapping Bose-Einstein condensates two different ${}^{87}\mathrm{Rb}$ hyperfine states [C. J. Myatt et al., Phys. Rev. Lett. 78, 586 (1997)]. Despite complicated geometry, we have completed three-dimensional Hartree-Fock calculation coupled condensates. The explains number its key properties: (i) manner which one condensate partially wraps around other, (ii) mean separation between including...

We identify two qualitatively different mechanisms that control three-body recombination in a spin-polarized gas near zero temperature. A universal curve describes the rate versus two-body scattering length $a$. It grows as ${a}^{4}$ for large $|a|,$ with $a<0$ and $a>0$. Our calculations document previously established mechanism causes ${K}_{3}$ to grow rapidly $a$ increases toward $+\ensuremath{\infty}$, new tunneling produces an even stronger enhancement of...

We report the first experimental observation of nonadiabatic field-free orientation a heteronuclear diatomic molecule (CO) induced by an intense two-color (800 and 400 nm) femtosecond laser field. monitor measuring fragment ion angular distributions after Coulomb explosion with 800 nm pulse. The molecules is controlled relative phase results are compared to quantum mechanical rigid rotor calculations. demonstrated method can be applied study molecular frame dynamics under conditions in...

We review topics of current interest in the physics electronic, atomic and molecular scattering vicinity thresholds. Starting from phase space arguments, we discuss modifications Wigner law that are required to deal with by Coulomb, dipolar dispersion potentials, as well aspects threshold behaviour observed ultracold collisions. employ tools quantum defect semiclassical theories bring out rich variety behaviours. The discussion is then turned recent progress understanding many-body break-ups...

The adiabatic hyperspherical method is used to investigate the spectrum of helium trimer and explore effects on varying masses as well interaction strength. When a realistic dimer potential adopted, only two isotopic combinations are observed have three-body bound states: $^{4}\mathrm{He}_{3}$ $^{4}\mathrm{He}_{2}^{3}$He. By artificially adjusting potential, we also determine range strengths for which halo states can result. existence Efimov both physical unphysical systems examined....

Carrier-envelope phase difference effects in the dissociation of ${\mathrm{H}\mathrm{D}}^{+}$ molecular ion field an intense, linearly polarized, ultrashort laser pulse are studied framework time-dependent Schr\"odinger equation. We consider a reduced-dimensionality model which nuclei free to vibrate along polarization and electrons move two dimensions. The has central wavelength 790 nm length 10 fs with intensities range $6\ifmmode\times\else\texttimes\fi{}{10}^{14}$...

In recent years extensive theoretical and experimental studies of universal few-body physics have advanced our understanding Efimov physics. Whereas theory had been the driving force behind for decades, experiments contributed an unexpected discovery. Specifically, measurements found that so-called three-body parameter determining several properties system is universal, even though fundamental assumptions in effect suggest it should be a variable property depends on precise details...

We present a general framework for understanding carrier-envelope phase (CEP) effects in quantum system interacting with an intense, short laser pulse. establish simple connection between the CEP and wave function that can be exploited to obtain full dependence of observable given at single CEP. Within this framework, all are interpreted as interference different photon amplitudes which, turn, used put limits on pulse lengths intensities required see significant effects.

Measurements and calculations of the absolute carrier-envelope-phase (CEP) effects in photodissociation simplest molecule, ${\mathrm{H}}_{2}^{+}$, with a 4.5-fs Ti:sapphire laser pulse at intensities up to $(4\ifmmode\pm\else\textpm\fi{}2)\ifmmode\times\else\texttimes\fi{}{10}^{14}\text{ }\text{ }\mathrm{W}/{\mathrm{cm}}^{2}$ are presented. Localization electron respect two nuclei (during dissociation process) is controlled via CEP ultrashort pulses. In contrast previous CEP-dependent...

A key question concerning the three-body fragmentation of polyatomic molecules is distinction sequential and concerted mechanisms, i.e., stepwise or simultaneous cleavage bonds. Using laser-driven OCS into O^{+}+C^{+}+S^{+} employing coincidence momentum imaging, we demonstrate a novel method that enables clear separation breakup. The accomplished by analyzing in native frame associated with each step taking advantage rotation intermediate molecular fragment, CO^{2+} CS^{2+}, before its...

We have developed a method for calculating the rates three-body recombination of cold atoms. This allows us to treat not only zero total angular momentum, $J=0,$ states but also $J>0$ states, so that recombinations at nonzero collision energies can be considered. Our is applied ground-state helium atoms ${}^{4}\mathrm{He},$ using realistic interaction potential. In addition, we obtain induced dissociation.

I specialize the Hartree-Fock, random-phase, and configuration-interaction approximations to a system of interacting bosons in an external potential. This approach affords more direct connection methods language atomic-structure calculations. The derivations equations parallel those found atomic structure are contrasted with commonly used Bogoliubov for bosons. present numerical method solving Hartree-Fock random-phase obtain low-lying excitation energies trapped alkali-metal atoms.

We present a simple and unifying picture that provides the energy scattering length dependence for all inelastic three-body collision rates in ultracold regime systems with short-range two-body interactions. Here, we scaling laws vibrational relaxation, recombination, collision-induced dissociation support s-wave collisions. These include three identical bosons, two fermions. Our approach reproduces previous results, predicts several others, gives general form of cases.

We calculate binary collision parameters for mixtures of ultracold gases ${}^{85}\mathrm{Rb}$ and ${}^{87}\mathrm{Rb}$ atoms. predict a large positive triplet scattering length mixed-isotope collisions, which implies that stable double condensate can be formed by sympathetic evaporative cooling. Moreover, collisions between atoms in the lowest hyperfine manifold exhibit magnetic-field-induced Feshbach resonances should allow partial control interaction condensates. These considerations make...

We obtain the threshold laws for three-body recombination of particles interacting via short-range potentials, taking into account all combinations particle symmetry. In particular, we show that rate is constant at zero energy unless indistinguishable fermions are present. this case, suppressed by either a factor E or ${E}^{2}$ two three fermions, respectively. addition, present law collision-induced dissociation.

Laser-induced dissociation and ionization of $\mathrm{H}_{2}{}^{+}$ were simultaneously measured using coincidence 3D momentum imaging, allowing direct separation the two processes, even where fragment kinetic energy is same for both processes. The results 45 135 fs 790 nm pulses with an intensity approximately $2.5\ifmmode\times\else\texttimes\fi{}{10}^{14}\text{ }\text{ }\mathrm{W}/{\mathrm{cm}}^{2}$ differ from each other much more than one would expect previous measurements longer...

The recombination rate for three identical bosons has been calculated to test the limits of its universal behavior. It obtained several different collision energies and scattering lengths $a$ up ${10}^{5}\text{ }\text{ }\mathrm{a}\mathrm{.}\mathrm{u}\mathrm{.}$, giving rates that vary over 15 orders magnitude. We find behavior is limited threshold region characterized by $E\ensuremath{\lesssim}{\ensuremath{\hbar}}^{2}/2{\ensuremath{\mu}}_{12}{a}^{2}$, where $E$ total energy...

We have measured and explained a new mechanism of molecular ionization near the appearance intensity that produces sequence peaks in nuclear kinetic energy spectrum separated by photon energy. Our interpretation is based on an internally consistent model for motion during intense laser pulse. Within this model, same concepts language can be used both dissociation ionization, leading to more unified understanding dynamics.

High-order (three-photon or more) above-threshold dissociation (ATD) of ${\mathrm{H}}_{2}^{+}$ has generally not been observed using 800 nm light. We demonstrate a strong enhancement its probability intense 7 fs laser pulses interacting with beams ${\mathrm{H}}_{2}^{+}$, ${\mathrm{HD}}^{+}$, and ${\mathrm{D}}_{2}^{+}$ ions. The mechanism invokes dynamic control the pathway. These measurements are supported by theory that additionally reveals, for first time, an unexpectedly large...

The dissociation of $\mathrm{H}_{2}{}^{+}$ in an intense laser field has been experimentally studied using femtosecond pulses at $790\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ the intensity range ${10}^{13}--{10}^{15}\phantom{\rule{0.3em}{0ex}}\mathrm{W}∕{\mathrm{cm}}^{2}$. Kinematically complete measurements both ionic ${\mathrm{H}}^{+}$ and neutral H fragments dissociated from a vibrationally excited beam have achieved by coincidence three-dimensional momentum imaging system. Angular-resolved...

We report on the observation of an elementary exchange process in optically trapped ultracold sample atoms and Feshbach molecules. can magnetically control energetic nature tune it from endoergic to exoergic, enabling a pronounced threshold behavior. In contrast relaxation more deeply bound molecular states, does not lead trap loss. find excellent agreement between our experimental observations calculations based solutions three-body Schr\"odinger equation adiabatic hyperspherical...

The $^{4}\mathrm{He}_{3}$ system is studied using the adiabatic hyperspherical representation. We adopt current state-of-the-art helium interaction potential including retardation and nonadditive three-body term to calculate all low-energy properties of triatomic $^{4}\mathrm{He}$ system. bound state energies trimer are computed as well $^{4}\mathrm{He}+^{4}\mathrm{He}_{2}$ elastic scattering cross sections, recombination, collision induced dissociation rates at finite temperatures. also...

We discuss several issues important for experimentally observing Efimov physics in ultracold quantum gases. By numerically solving the three-boson Schrödinger equation over a broad range of scattering lengths and energies, by including model potentials with multiple bound states, we address complications relating experimental observations to available analytic expressions. These more realistic introduce features that can mask predicted at small lengths. They also allow us verify positive...

The dissociation of an H$_2^+$ molecular-ion beam by linearly polarized, carrier-envelope-phase-tagged 5 fs pulses at 4$\times10^{14} $W/cm$^2$ with a central wavelength 730 nm was studied using coincidence 3D momentum imaging technique. Carrier-envelope-phase-dependent asymmetries in the emission direction H$^+$ fragments relative to laser polarization were observed. These are caused interference odd and even photon number pathways, where net-zero 1-photon predominantly contributes H$^+$+H...