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Journal ArticleDOI

Rovibrational dynamics of the strontium molecule in the AΣu+1, c3Πu, and aΣu+3 manifold from state-of-the-art ab initio calculations

18 May 2012-Journal of Chemical Physics (American Institute of Physics)-Vol. 136, Iss: 19, pp 194306
TL;DR: In this article, the potential energy curves and transition moments were obtained with the linear response (equation of motion) coupled cluster method limited to single, double, and linear triple excitations for the potentials and limited to double excitations and transition moment for the transition moments.
Abstract: State-of-the-art ab initio techniques have been applied to compute the potential energy curves for the electronic states in the AΣu+1, c3Πu, and aΣu+3 manifold of the strontium dimer, the spin-orbit and nonadiabatic coupling matrix elements between the states in the manifold, and the electric transition dipole moment from the ground XΣg+1 to the nonrelativistic and relativistic states in the A+c+a manifold. The potential energy curves and transition moments were obtained with the linear response (equation of motion) coupled cluster method limited to single, double, and linear triple excitations for the potentials and limited to single and double excitations for the transition moments. The spin-orbit and nonadiabatic coupling matrix elements were computed with the multireference configuration interaction method limited to single and double excitations. Our results for the nonrelativistic and relativistic (spin-orbit coupled) potentials deviate substantially from recent ab initio calculations. The potential...
Citations
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Journal ArticleDOI
TL;DR: In this paper, the authors characterize the properties of deeply subradiant molecular states with intrinsic quality factors exceeding 1013 via precise optical spectroscopy with the longest molecule-light coherent interaction times to date.
Abstract: An experimental study characterizes subradiance—inhibited emission due to destructive interference—in ultracold molecules close to the dissociation limit and shows that it could be used for precision molecular spectroscopy. Weakly bound molecules have physical properties without atomic analogues, even as the bond length approaches dissociation. For instance, the internal symmetries of homonuclear diatomic molecules result in the formation of two-body superradiant and subradiant excited states. Whereas superradiance1,2,3 has been demonstrated in a variety of systems, subradiance4,5,6 is more elusive owing to the inherently weak interaction with the environment. Here we characterize the properties of deeply subradiant molecular states with intrinsic quality factors exceeding 1013 via precise optical spectroscopy with the longest molecule–light coherent interaction times to date. We find that two competing effects limit the lifetimes of the subradiant molecules, with different asymptotic behaviours. The first is radiative decay via weak magnetic-dipole and electric-quadrupole interactions. We prove that its rate increases quadratically with the bond length, confirming quantum mechanical predictions. The second is non-radiative decay through weak gyroscopic predissociation, with a rate proportional to the vibrational mode spacing and sensitive to short-range physics. This work bridges the gap between atomic and molecular metrology based on lattice-clock techniques7, enhancing our understanding of long-range interatomic interactions.

96 citations

Journal ArticleDOI
TL;DR: In this article, a diatomic molecule in a spatially degenerate electronic state interacting with a non-resonant laser field and investigating its rovibrational structure in the presence of the field was investigated.
Abstract: We formulate the theory for a diatomic molecule in a spatially degenerate electronic state interacting with a non-resonant laser field and investigate its rovibrational structure in the presence of the field. We report on ab initio calculations employing the double electron attachment intermediate Hamiltonian Fock space coupled cluster method restricted to single and double excitations for all electronic states of the Rb2 molecule up to 5s+5d dissociation limit of about 26,000 cm−1. In order to correctly predict the spectroscopic behaviour of Rb2, we have also calculated the electric transition dipole moments, non-adiabatic coupling and spin-orbit coupling matrix elements, and static dipole polarisabilities, using the multireference configuration interaction method. When a molecule is exposed to strong non-resonant light, its rovibrational levels get hybridised. We study the spectroscopic signatures of this effect for transitions between the X1Σ+ g electronic ground state and the A1Σ+ u and b3Π u excited ...

73 citations

Journal ArticleDOI
TL;DR: In this paper, a state-insensitive magic lattice trap is used to weakly couples to molecular vibronic resonances and enhances the coherence time of light-induced clock state superpositions by several orders of magnitude.
Abstract: Atomic lattice clocks have spurred numerous ideas for tests of fundamental physics, detection of general relativistic effects and studies of interacting many-body systems. On the other hand, molecular structure and dynamics offer rich energy scales that are at the heart of new protocols in precision measurement and quantum information science. Here, we demonstrate a fundamentally distinct type of lattice clock that is based on vibrations in diatomic molecules, and present coherent Rabi oscillations between weakly and deeply bound molecules that persist for tens of milliseconds. This control is made possible by a state-insensitive magic lattice trap that weakly couples to molecular vibronic resonances and enhances the coherence time of light-induced clock state superpositions by several orders of magnitude. The achieved quality factor Q = 8 × 1011 results from 30 Hz narrow resonances for a 25 THz clock transition in Sr2 molecules. Our technique of extended coherent manipulation is applicable to long-term storage of quantum information in qubits based on ultracold polar molecules, while the vibrational clock enables precise probes of interatomic forces, tests of Newtonian gravitation at ultrashort range and model-independent searches for electron-to-proton mass ratio variations. The realization of a molecular lattice clock based on vibrations in diatomic molecules is reported with coherence times lasting over tens of milliseconds, which is enabled by the use of a state-insensitive magic lattice trap.

72 citations

Journal ArticleDOI
07 Jul 2016-Nature
TL;DR: The experimental ability to produce well-defined quantum continuum states at low energies will enable high-precision studies of long-range molecular potentials for which accurate quantum chemistry models are unavailable, and may serve as a source of entangled states and coherent matter waves for a wide range of experiments in quantum optics.
Abstract: The photodissociation of 88Sr2 molecules is examined at ultracold temperatures with a high degree of control, and a wealth of quantum effects such as barrier tunnelling, matter—wave interference of reaction products and forbidden pathways are observed Chemistry is beginning to benefit from the advances made by atomic physicists working with ultracold molecules. In particular, reaching the quantum regime and looking at basic chemical processes in this regime could yield rich insights into the basic building blocks of chemistry. Here, Tanya Zelevinsky and colleagues look at the photodissociation of ultracold 88Sr2 molecules and cleanly observe a wealth of quantum effects, including barrier tunnelling, matter–wave interference of reaction products and forbidden reaction pathways. The high level of control may allow for high-precision measurement of important quantities, such as long-range molecular potentials, in the future. Chemical reactions at ultracold temperatures are expected to be dominated by quantum mechanical effects. Although progress towards ultracold chemistry has been made through atomic photoassociation1, Feshbach resonances2 and bimolecular collisions3, these approaches have been limited by imperfect quantum state selectivity. In particular, attaining complete control of the ground or excited continuum quantum states has remained a challenge. Here we achieve this control using photodissociation, an approach that encodes a wealth of information in the angular distribution of outgoing fragments. By photodissociating ultracold 88Sr2 molecules with full control of the low-energy continuum, we access the quantum regime of ultracold chemistry, observing resonant and nonresonant barrier tunnelling, matter–wave interference of reaction products and forbidden reaction pathways. Our results illustrate the failure of the traditional quasiclassical model of photodissociation4,5,6,7 and instead are accurately described by a quantum mechanical model8,9. The experimental ability to produce well-defined quantum continuum states at low energies will enable high-precision studies of long-range molecular potentials for which accurate quantum chemistry models are unavailable, and may serve as a source of entangled states and coherent matter waves for a wide range of experiments in quantum optics10,11.

64 citations

Journal ArticleDOI
TL;DR: In this paper, the double electron attachment intermediate Hamiltonian Fock space coupled cluster method was used to estimate the rovibrational structure of a diatomic molecule in a spatially degenerate electronic state interacting with a non-resonant laser field and investigate its structure in the presence of the field.
Abstract: We formulate the theory for a diatomic molecule in a spatially degenerate electronic state interacting with a non-resonant laser field and investigate its rovibrational structure in the presence of the field. We report on \textit{ab initio} calculations employing the double electron attachment intermediate Hamiltonian Fock space coupled cluster method restricted to single and double excitations for all electronic states of the Rb$_2$ molecule up to $5s+5d$ dissociation limit of about 26.000$\,$cm$^{-1}$. In order to correctly predict the spectroscopic behavior of Rb$_2$, we have also calculated the electric transition dipole moments, non-adiabatic coupling and spin-orbit coupling matrix elements, and static dipole polarizabilities, using the multireference configuration interaction method. When a molecule is exposed to strong non-resonant light, its rovibrational levels get hybridized. We study the spectroscopic signatures of this effect for transitions between the X$^1\Sigma_g^+$ electronic ground state and the A$^1\Sigma_u^+$ and b$^3\Pi_u$ excited state manifold. The latter is characterized by strong perturbations due to the spin-orbit interaction. We find that for non-resonant field strengths of the order $10^9$W/cm$^2$, the spin-orbit interaction and coupling to the non-resonant field become comparable. The non-resonant field can then be used to control the singlet-triplet character of a rovibrational level.

59 citations

References
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Journal ArticleDOI
TL;DR: In this paper, a direct difference method for the computation of molecular interactions has been based on a bivariational transcorrelated treatment, together with special methods for the balancing of other errors.
Abstract: A new direct difference method for the computation of molecular interactions has been based on a bivariational transcorrelated treatment, together with special methods for the balancing of other errors. It appears that these new features can give a strong reduction in the error of the interaction energy, and they seem to be particularly suitable for computations in the important region near the minimum energy. It has been generally accepted that this problem is dominated by unresolved difficulties and the relation of the new methods to these apparent difficulties is analysed here.

19,483 citations

Journal ArticleDOI
TL;DR: In this paper, a simple expression for the radial dependent damping functions for the individual dispersion coefficients C2n for arbitrary even orders 2n was derived for the well region of the atom van der Waals potential with only five essential parameters A, b, C6, C8, and C10.
Abstract: Starting from our earlier model [J. Chem. Phys. 66, 1496 (1977)] a simple expression is derived for the radial dependent damping functions for the individual dispersion coefficients C2n for arbitrary even orders 2n. The damping functions are only a function of the Born–Mayer range parameter b and thus can be applied to all systems for which this is known or can be estimated. For H(1S)–H(1S) the results are in almost perfect agreement with the very accurate recent ab initio damping functions of Koide, Meath, and Allnatt. Comparisons with less accurate previous calculations for other systems also show a satisfactory agreement. By adding a Born–Mayer repulsive term [A exp(−bR)] to the damped dispersion potential, a simple universal expression is obtained for the well region of the atom–atom van der Waals potential with only five essential parameters A, b, C6, C8, and C10. The model has been tested for the following representative systems: H2 3Σ, He2, and Ar2 as well as NaK 3Σ and LiHg, which include four che...

1,381 citations

Journal ArticleDOI
David DeMille1
TL;DR: This design can plausibly lead to a quantum computer with greater, approximately > or = 10(4) qubits, which can perform approximately 10(5) CNOT gates in the anticipated decoherence time of approximately 5 s.
Abstract: We propose a novel physical realization of a quantum computer. The qubits are electric dipole moments of ultracold diatomic molecules, oriented along or against an external electric field. Individual molecules are held in a 1D trap array, with an electric field gradient allowing spectroscopic addressing of each site. Bits are coupled via the electric dipole-dipole interaction. Using technologies similar to those already demonstrated, this design can plausibly lead to a quantum computer with $\ensuremath{\gtrsim}{10}^{4}$ qubits, which can perform $\ensuremath{\sim}{10}^{5}$ CNOT gates in the anticipated decoherence time of $\ensuremath{\sim}5\mathrm{s}$.

1,164 citations

Journal ArticleDOI
TL;DR: The linear and quadratic response functions have been determined for a coupled cluster reference state from the response functions, computationally tractable expressions have been derived for excitation energies, first and second-order matrix transition elements, transition matrix elements between excited states, and second and third-order frequency-dependent molecular properties as discussed by the authors.
Abstract: The linear and quadratic response functions have been determined for a coupled cluster reference state From the response functions, computationally tractable expressions have been derived for excitation energies, first‐ and second‐order matrix transition elements, transition matrix elements between excited states, and second‐ and third‐order frequency‐dependent molecular properties

1,001 citations

Journal ArticleDOI
12 Feb 2010-Science
TL;DR: Experimental evidence for exothermic atom-exchange chemical reactions is reported, starting with an optically trapped near–quantum-degenerate gas of polar 40K87Rb molecules prepared in their absolute ground state.
Abstract: How does a chemical reaction proceed at ultralow temperatures? Can simple quantum mechanical rules such as quantum statistics, single partial-wave scattering, and quantum threshold laws provide a clear understanding of the molecular reactivity under a vanishing collision energy? Starting with an optically trapped near-quantum-degenerate gas of polar 40K87Rb molecules prepared in their absolute ground state, we report experimental evidence for exothermic atom-exchange chemical reactions. When these fermionic molecules were prepared in a single quantum state at a temperature of a few hundred nanokelvin, we observed p-wave-dominated quantum threshold collisions arising from tunneling through an angular momentum barrier followed by a short-range chemical reaction with a probability near unity. When these molecules were prepared in two different internal states or when molecules and atoms were brought together, the reaction rates were enhanced by a factor of 10 to 100 as a result of s-wave scattering, which does not have a centrifugal barrier. The measured rates agree with predicted universal loss rates related to the two-body van der Waals length.

757 citations