Stability of triplet rubidium ground-state molecules

Experiments involving ultracold molecules require sufficiently long lifetimes, which can be very short for excited rovibrational states in the molecular potentials. For alkali-metal atoms such as rubidium, a lowest rovibrational molecular state can both be found in the electronic singlet and triplet configurations. The molecular singlet ground state is absolutely stable. However, the lowest triplet state can decay to a deeper bound singlet molecule due to a radiative decay mechanism that involves the interatomic spin-orbit interaction. We investigate this mechanism, and find the lifetime of rubidium molecules in the lowest triplet rovibrational state to be about 20 min.Experiments involving ultracold molecules require sufficiently long lifetimes, which can be very short for excited rovibrational states in the molecular potentials. For alkali-metal atoms such as rubidium, a lowest rovibrational molecular state can both be found in the electronic singlet and triplet configurations. The molecular singlet ground state is absolutely stable. However, the lowest triplet state can decay to a deeper bound singlet molecule due to a radiative decay mechanism that involves the interatomic spin-orbit interaction. We investigate this mechanism, and find the lifetime of rubidium molecules in the lowest triplet rovibrational state to be about 20 min.

arXiv:1412.5799Physical Review AApr 14, 20172 citations

Short-pulse photoassociation in rubidium below the D1 line

Christiane P. Koch, Ronnie Kosloff, Françoise Masnou-Seeuws

Photoassociation of two ultracold rubidium atoms and the subsequent formation of stable molecules in the singlet ground and lowest triplet states is investigated theoretically. The method employs laser pulses inducing transitions via excited states correlated to the $5S+5{P}_{1∕2}$ asymptote. Weakly bound molecules in the singlet ground or lowest triplet state can be created by a single pulse while the formation of more deeply bound molecules requires a two-color pump-dump scenario. More deeply bound molecules in the singlet ground or lowest triplet state can be produced only if efficient mechanisms for both pump and dump steps exist. While long-range $1∕{R}^{3}$ potentials allow for efficient photoassociation, stabilization is facilitated by the resonant spin-orbit coupling of the ${0}_{u}^{+}$ states. Molecules in the singlet ground state bound by a few wave numbers can thus be formed. This provides a promising first step toward ground-state molecules which are ultracold in both translational and vibrational degrees of freedom.Photoassociation of two ultracold rubidium atoms and the subsequent formation of stable molecules in the singlet ground and lowest triplet states is investigated theoretically. The method employs laser pulses inducing transitions via excited states correlated to the $5S+5{P}_{1∕2}$ asymptote. Weakly bound molecules in the singlet ground or lowest triplet state can be created by a single pulse while the formation of more deeply bound molecules requires a two-color pump-dump scenario. More deeply bound molecules in the singlet ground or lowest triplet state can be produced only if efficient mechanisms for both pump and dump steps exist. While long-range $1∕{R}^{3}$ potentials allow for efficient photoassociation, stabilization is facilitated by the resonant spin-orbit coupling of the ${0}_{u}^{+}$ states. Molecules in the singlet ground state bound by a few wave numbers can thus be formed. This provides a promising first step toward ground-state molecules which are ultracold in both translational and vibrational degrees of freedom.

arXiv:physics/0511235Physical Review AApr 13, 200673 citations

Production, detection and trapping of ultracold molecular rubidium

Yiyan Huang

Production and state-selective detection of ultracold molecular rubidium (85Rb2) in the singlet ground state and the metastable triplet state are described. Ultracold 85Rb2 molecules are produced via photoassociation followed by radiative decay. State-selective detection of high-ν ground-state and metastable-state molecules is carried out by resonant Two-photon ionization (R2PI) with a pulsed laser. The spectra of both the ground singlet and metastable triplet states are investigated. Spectroscopy of several intermediate excited states, some of which are observed for the first time, is also studied. Mixing between excited singlet and triplet states is observed in both the singlet and triplet spectra. A proposal for producing ν = 0 ground-state molecules by utilizing this singlet-triplet mixing is given. Magnetic trapping and filtering of metastable triplet-state molecules is also described, and a scheme for optical trapping of molecules is proposed.^Production and state-selective detection of ultracold molecular rubidium (85Rb2) in the singlet ground state and the metastable triplet state are described. Ultracold 85Rb2 molecules are produced via photoassociation followed by radiative decay. State-selective detection of high-ν ground-state and metastable-state molecules is carried out by resonant Two-photon ionization (R2PI) with a pulsed laser. The spectra of both the ground singlet and metastable triplet states are investigated. Spectroscopy of several intermediate excited states, some of which are observed for the first time, is also studied. Mixing between excited singlet and triplet states is observed in both the singlet and triplet spectra. A proposal for producing ν = 0 ground-state molecules by utilizing this singlet-triplet mixing is given. Magnetic trapping and filtering of metastable triplet-state molecules is also described, and a scheme for optical trapping of molecules is proposed.^

Jan 1, 20064 citations

Short-Range Photoassociation and Trilobite-Like States of Ultracold Rb2

Michael Bellos

I demonstrate the formation of rubidium dimers via photoassociation and spontaneous emission at short internuclear distances. This short-range photoassociation allows the formation of deeply bound molecules, including, for instance, the lowest rovibrational level of the lowest triplet state: a(0,0). This particular state is interesting because it is metastable against radiative decay, and possibly long-lived in optical and/or magnetic traps. In a second experiment, I demonstrate the population of trilobite-like excited states of Rb2. Trilobite-like states are bound by an unusual chemical bond, and can have large physical dimensions and electric dipole moments. I demonstrate the population of these states through the ultraviolet excitation of weakly bound molecules. By using the same ultraviolet excitation scheme, I place a new upper-bound on the minimum energy required to ionize 85Rb2 molecules.I demonstrate the formation of rubidium dimers via photoassociation and spontaneous emission at short internuclear distances. This short-range photoassociation allows the formation of deeply bound molecules, including, for instance, the lowest rovibrational level of the lowest triplet state: a(0,0). This particular state is interesting because it is metastable against radiative decay, and possibly long-lived in optical and/or magnetic traps. In a second experiment, I demonstrate the population of trilobite-like excited states of Rb2. Trilobite-like states are bound by an unusual chemical bond, and can have large physical dimensions and electric dipole moments. I demonstrate the population of these states through the ultraviolet excitation of weakly bound molecules. By using the same ultraviolet excitation scheme, I place a new upper-bound on the minimum energy required to ionize 85Rb2 molecules.

Jan 1, 20131 citation

Polarizability of ultracold molecules in the rovibrational ground state of

Markus Deiß, Björn Drews, Johannes Hecker Denschlag +3 more

Abstract We study, both theoretically and experimentally, the dynamical polarizability of molecules in the rovibrational ground state of . Taking all relevant excited molecular bound states into account, we compute the complex-valued polarizability for wave numbers up to 20 000 . Our calculations are compared to experimental results at ( ) as well as at ( ). Here, we discuss the measurements at . The ultracold Rb2 molecules are trapped in the lowest Bloch band of a 3D optical lattice. Their polarizability is determined by lattice modulation spectroscopy which measures the potential depth for a given light intensity. Moreover, we investigate the decay of molecules in the optical lattice, where lifetimes of more than are observed. In addition, the dynamical polarizability for the state is calculated. We provide simple analytical expressions that reproduce the numerical results for for all vibrational levels of as well as . Precise knowledge of the molecular polarizability is essential for designing experiments with ultracold molecules as lifetimes and lattice depths are key parameters. Specifically the wavelength at is of interest, since here, ultrastable high power lasers are available.Abstract We study, both theoretically and experimentally, the dynamical polarizability of molecules in the rovibrational ground state of . Taking all relevant excited molecular bound states into account, we compute the complex-valued polarizability for wave numbers up to 20 000 . Our calculations are compared to experimental results at ( ) as well as at ( ). Here, we discuss the measurements at . The ultracold Rb2 molecules are trapped in the lowest Bloch band of a 3D optical lattice. Their polarizability is determined by lattice modulation spectroscopy which measures the potential depth for a given light intensity. Moreover, we investigate the decay of molecules in the optical lattice, where lifetimes of more than are observed. In addition, the dynamical polarizability for the state is calculated. We provide simple analytical expressions that reproduce the numerical results for for all vibrational levels of as well as . Precise knowledge of the molecular polarizability is essential for designing experiments with ultracold molecules as lifetimes and lattice depths are key parameters. Specifically the wavelength at is of interest, since here, ultrastable high power lasers are available.

arXiv:1501.03793New Journal of PhysicsJun 1, 201515 citations

Inelastic collisions of ultracold triplet Rb2 molecules in the rovibrational ground state

Björn Drews, Markus Deiß, Krzysztof Jachymski +2 more

Abstract Exploring and controlling inelastic and reactive collisions on the quantum level is a main goal of the developing field of ultracold chemistry. For this, the preparation of precisely defined initial atomic and molecular states in tailored environments is necessary. Here we present experimental studies of inelastic collisions of metastable ultracold Rb2 molecules in an array of quasi-1D potential tubes. In particular, we investigate collisions of molecules in the absolute lowest triplet energy level where any inelastic process requires a change of the electronic state. Remarkably, we find similar decay rates as for collisions between rotationally or vibrationally excited triplet molecules where other decay paths are also available. The decay rates are close to the ones for universal reactions but vary considerably when confinement and collision energy are changed. This might be exploited to control the collisional properties of molecules.Abstract Exploring and controlling inelastic and reactive collisions on the quantum level is a main goal of the developing field of ultracold chemistry. For this, the preparation of precisely defined initial atomic and molecular states in tailored environments is necessary. Here we present experimental studies of inelastic collisions of metastable ultracold Rb2 molecules in an array of quasi-1D potential tubes. In particular, we investigate collisions of molecules in the absolute lowest triplet energy level where any inelastic process requires a change of the electronic state. Remarkably, we find similar decay rates as for collisions between rotationally or vibrationally excited triplet molecules where other decay paths are also available. The decay rates are close to the ones for universal reactions but vary considerably when confinement and collision energy are changed. This might be exploited to control the collisional properties of molecules.

arXiv:1606.00722Nature CommunicationsMar 23, 201723 citations

5S+5{P}_{1∕2}

asymptote. Weakly bound molecules in the singlet ground or lowest triplet state can be created by a single pulse while the formation of more deeply bound molecules requires a two-color pump-dump scenario. More deeply bound molecules in the singlet ground or lowest triplet state can be produced only if efficient mechanisms for both pump and dump steps exist. While long-range

1∕{R}^{3}

potentials allow for efficient photoassociation, stabilization is facilitated by the resonant spin-orbit coupling of the

{0}_{u}^{+}

states. Molecules in the singlet ground state bound by a few wave numbers can thus be formed. This provides a promising first step toward ground-state molecules which are ultracold in both translational and vibrational degrees of freedom.