arXiv subjects

B. D. Esry

Publications and source records attributed to B. D. Esry.

At least 37 records · Page 2Linked to original sources

arXiv2009

Field-free orientation of CO molecules by femtosecond two-color laser fields

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

physics.chem-ph↗

arXiv2009

Conditions for Efimov Physics for Finite Range Potentials

We consider a system of three identical bosons near a Feshbach resonance in the universal regime with large scattering length usually described by model independent zero-range potentials. We employ the adiabatic hyperspherical approximation and derive the rigorous large-distance equation for the adiabatic potential for finite-range interactions. The effective range correction to the zero-range approximation must be supplemented by a new term of the same order. The non-adiabatic term can be decisive. Efimov physics is always confined to the range between effective range and scattering length. The analytical results agree with numerical calculations for realistic potentials.

quant-ph↗

arXiv2009

Ultracold three-body collisions near overlapping Feshbach resonances

We present a comprehensive collection of ultracold three-body collisions properties near overlapping Feshbach resonances. Our results incorporate variations of all scattering lengths and demonstrate novel collisional behavior, such as atom-molecule interference effects. Taking advantage of the unique ways in which these collisions reflect Efimov physics, new pathways to control atomic and molecular losses open up. Further, we show that overlapping resonances can greatly improve the chances of observing multiple Efimov features in an ultracold quantum gas for nearly any system.

physics.atom-ph↗

arXiv2008

Adiabatic hyperspherical study of triatomic helium systems

The 4He3 system is studied using the adiabatic hyperspherical representation. We adopt the current state-of-the-art helium interaction potential including retardation and the nonadditive three-body term, to calculate all low-energy properties of the triatomic 4He system. The bound state energies of the 4He trimer are computed as well as the 4He+4He2 elastic scattering cross sections, the three-body recombination and collision induced dissociation rates at finite temperatures. We also treat the system that consists of two 4He and one 3He atoms, and compute the spectrum of the isotopic trimer 4He2 3He, the 3He+4He2 elastic scattering cross sections, the rates for three-body recombination and the collision induced dissociation rate at finite temperatures. The effects of retardation and the nonadditive three-body term are investigated. Retardation is found to be significant in some cases, while the three-body term plays only a minor role for these systems.

physics.atom-ph↗

arXiv2008

Efimov Trimer Formation via Ultracold Four-body Recombination

We discuss the collisional formation of Efimov trimers via ultracold four-body recombination. In particular, we consider the reaction A+A+A+B->A3+B with A and B ultracold atoms. We obtain expressions for the four-body recombination rate and show that it reflects the three-body Efimov physics either as a function of collision energy or as a function of the two-body s-wave scattering length between A atoms. In addition, we briefly discuss issues important for experimentally observing this interesting and relatively unexplored process.

quant-ph↗

arXiv2008

The short-range three-body phase and other issues impacting the observation of Efimov physics in ultracold quantum gases

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, and by including model potentials with multiple bound states, we address the complications of relating experimental observations to available analytic expressions. These more realistic potentials introduce features that can mask the predicted Efimov physics at small scattering lengths. They also allow us to verify that positive and negative scattering lengths are universally connected only across a pole, not across a zero. Additionally, we show that the spacing between Efimov features for the relatively small scattering lengths accessible experimentally fail to precisely follow the geometric progression expected for Efimov physics. Finally, we emphasize the importance of the short-range three-body physics in determining the position of Efimov features and show that theoretically reproducing two-body physics is not generally sufficient to predict three-body properties quantitatively.

cond-mat.other↗

arXiv2008

Ultracold atom-molecule collisions with fermionic atoms

Elastic and inelastic properties of weakly bound s- and p-wave molecules of fermionic atoms that collide with a third atom are investigated. Analysis of calculated collisional properties of s-wave dimers of fermions in different spin states permit us to compare and highlight the physical mechanisms that determine the stability of s-wave and p-wave molecules. In contrast to s-wave molecules, the collisional properties of p-wave molecules are found to be largely insensitive to variations of the p-wave scattering length and that these collisions will usually result in short molecular lifetimes. We also discuss the importance of this result for both theories and experiments involving degenerate Fermi gases.

physics.atom-ph↗

arXiv2007

Suppression of molecular decay in ultracold gases without Fermi statistics

We study inelastic processes for ultracold three-body systems in which only one interaction is resonant. We have found that the decay rates for weakly bound molecules due to collisions with other atoms can be suppressed not only without fermionic statistics but also when bosonic statistics applies. In addition, we show that at ultracold temperatures three-body recombination involving a single resonant pair of atoms leads mainly to formation of weakly bound molecules which, in turn, are stable against decay. These results indicate that recombination in three-component atomic gases can be used as an efficient mechanism for molecular formation, allowing the achievement of high molecular densities.

physics.atom-ph↗

arXiv2007

Three-Body Recombination in One Dimension

We study the three-body problem in one dimension for both zero and finite range interactions using the adiabatic hyperspherical approach. Particular emphasis is placed on the threshold laws for recombination, which are derived for all combinations of the parity and exchange symmetries. For bosons, we provide a numerical demonstration of several universal features that appear in the three-body system, and discuss how certain universal features in three dimensions are different in one dimension. We show that the probability for inelastic processes vanishes as the range of the pair-wise interaction is taken to zero and demonstrate numerically that the recombination threshold law manifests itself for large scattering length.

quant-ph↗

arXiv2006

Unitary theory of laser Carrier-Envelope Phase effects

We consider a quantum state interacting with a short intense linearly polarized laser pulse. Using the two-dimensional time representation and Floquet picture we establish a straightforward connection between the laser carrier-envelope phase (CEP) and the wave function. This connection is revealed as a unitary transformation in the space of Floquet components. It allows any CEP effect to be interpreted as an interference between the components and to put limits on using the CEP in coherent control. A 2-level system is used to illustrate the theory. On this example we demonstrate strong intensity sensitivity of the CEP effects and predict an effect for pulses much longer than the oscillation period of the carrier.

physics.atom-ph↗

arXiv2005

Three-body systems with attractive 1/r potentials

We have used the hyperspherical adiabatic representation to describe the system of three identical bosons in an spin stretched state interacting by an attractive 1/r potential. A proposal has been made how such a system might be realized experimentally in cold trapped atoms using extremely off-resonant laser fields [Phys. Rev. Lett. 84, 5687 (2000)]. We have obtained effective potentials, channel functions, and nonadiabatic couplings for this gravity-like interaction, allowing us to calculate the ground state energy with accuracy that substantially improves upon previous results. We have similarly calculated the energies for the first four 0^+ excited states. These results show that the simple adiabatic hyperspherical approximation offers an accurate description for such a system.

physics.atom-ph↗

arXiv2005

Enhancing the Observability of the Efimov Effect in Ultracold Atomic Gas Mixtures

We discuss the prospects for observing the characteristic features of the Efimov effect in a two-component ultracold atomic gas near an interspecies Feshbach resonance. In the ultracold regime, the Efimov effect is expected to be manifested in the three-body collision rates through the appearance of series of minima or maxima as a function of the two-body s-wave scattering length $a$. Here, we propose the observation of this Efimov physics through measurements of the inelastic three-body rate constants near a Feshbach resonance. Our analysis suggests that boson-fermion mixtures, where the bosons are much heavier than the fermions, are the most favorable system to observe such features.

cond-mat.other↗

arXiv2005

Mass Dependence of Ultracold Three-Body Collision Rates

We show that many aspects of ultracold three-body collisions can be controlled by choosing the mass ratio between the collision partners. In the ultracold regime, the scattering length dependence of the three-body rates can be substantially modified from the equal mass results. We demonstrate that the only non-trivial mass dependence is due solely to Efimov physics. We have determined the mass dependence of the three-body collision rates for all heteronuclear systems relevant for two-component atomic gases with resonant s-wave interspecies interactions, which includes only three-body systems with two identical bosons or two identical fermions.

physics.atom-ph↗

arXiv2005

Manifestations of the Efimov Effect for Three Identical Bosons

In this paper we present results from numerical calculations for three identical boson systems for both very large and infinite two-body s-wave scattering length $a$. We have considered scattering lengths up to $2\times 10^5$ a.u. and solved the hyperangular part of the Schrödinger equation for distances up to $10^6$ a.u.. Form these, we obtained the three-body effective potentials, hyperspherical channel functions and the asymptotic behavior of the nonadiabatic couplings in order to to characterize the main aspects of the Efimov states. These results allow us to test and quantify the assumptions related to the Efimov effect.

cond-mat.other↗

arXiv2004

Scattering Length Scaling Laws for Ultracold Three-Body Collisions

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

cond-mat.other↗

arXiv2004

Transverse excitations of ultracold matter waves upon propagation past abrupt waveguide changes

The propagation of ultracold atomic gases through abruptly changing waveguide potentials is examined in the limit of non-interacting atoms. Time-independent scattering calculations of microstructured waveguides with discontinuous changes in the transverse harmonic binding potentials are used to mimic waveguide perturbations and imperfections. Three basic configurations are examined: step-like, barrier-like and well-like with waves incident in the ground mode. At low energies, the spectra rapidly depart from single-moded, with significant transmission and reflection of excited modes. The high-energy limit sees 100 percent transmission, with the distribution of the transmitted modes determined simply by the overlap of the mode wave functions and interference.

physics.atom-ph↗

arXiv2004

Limits on Universality in Ultracold Three-Boson Recombination

The recombination rate for three identical bosons has been calculated to test the limits of its universal behavior. It has been obtained for several different collision energies and scattering lengths (a) up to 10^5 a.u., giving rates that vary over 15 orders of magnitude. We find that universal behavior is limited to the threshold region characterized by E lesssim hbar^2/(2mu_{12}a^2), where E is the total energy and mu_{12} is the two-body reduced mass. The analytically predicted infinite series of resonance peaks and interference minima is truncated to no more than three of each for typical experimental parameters.

physics.atom-ph↗

arXiv2004

Classical aspects of ultracold atom wavepacket motion through microstructured waveguide bends

The properties of low-density, low-energy matter wavepackets propagating through waveguide bends are investigated. Time-dependent quantum mechanical calculations using simple harmonic oscillator confining potentials are performed for a range of parameters close to those accessible by recent ``atom chip''-based experiments. We compare classical calculations based on Ehrenfest's theorem to these results to determine whether classical mechanics can predict the amount of transverse excitation as measured by the transverse heating. The present results thus elucidate some of the limits for which matter wave propagation through microstructures can be reliably considered using classical particle motion.

physics.atom-ph↗