A supersonic beam of cold lithium hydride molecules

Tokunaga, S. K.; Stack, J. O.; Hudson, J. J.; Sauer, B. E.; Hinds, E. A.; Tarbutt, M. R.

doi:10.1063/1.2711434

Cited by 21 publications

(24 citation statements)

References 32 publications

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“…For example, in the experiment reported in Ref. [6], 90% of the observed cold LiH molecules were in their electronic and rovibrational ground state X 1 Σ + . The cold molecule and the room-temperature surface are thus strongly out of equilibrium with respect to each other, so a study of the CP interaction necessitates that account be taken of the full non-equilibrium dynamics of the rotational and vibrational degrees of freedom of the cold molecule coupled to its thermal envi-ronment.…”

Section: Introductionmentioning

confidence: 99%

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Dynamics of thermal Casimir-Polder forces on polar molecules

2009

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We study the influence of thermal Casimir-Polder forces on the near-surface trapping of cold polar molecules, with emphasis on LiH and YbF near an Au surface at room temperature. We show that even for a molecule initially prepared in its electronic and rovibrational ground state, the Casimir-Polder force oscillates with the molecule-wall separation. The non-resonant force and the evanescent part of the resonant force almost exactly cancel at high temperature which results in a saturation of the (attractive) force in this limit. This implies that the Casimir-Polder force on a fully thermalised molecule can differ dramatically from that obtained using a naïve perturbative expansion of the Lifshitz formula based on the molecular ground-state polarisability. A dynamical calculation reveals how the spatial oscillations die out on a typical time scale of several seconds as thermalisation of the molecule with its environment sets in.

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Section: Introductionmentioning

confidence: 99%

“…Recently, trapping of light molecules such as metastable CO in travelling potential wells near a chip surface was achieved [5]. Another light diatomic molecule that has received considerable attention due to its large dipole moment is LiH; and the production of supersonic beams of cold LiH has been reported [6].…”

Section: Introductionmentioning

confidence: 99%

Dynamics of thermal Casimir-Polder forces on polar molecules

2009

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“…The curves are the outcome of the rate-equation model using a constant background-gas collision rate of 0:17 s ÿ1 . existence of 4 isotopomers often considered an ideal candidate molecule [21], is especially sensitive to blackbody radiation: even at 77 K it can only be trapped for a few seconds. At 4 K the rates for all molecules are smaller than 10 ÿ3 .…”

Section: Prl 98 133001 (2007) P H Y S I C a L R E V I E W L E T T E mentioning

confidence: 99%

Optical Pumping of Trapped Neutral Molecules by Blackbody Radiation

et al. 2007

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Optical pumping by blackbody radiation is a feature shared by all polar molecules and fundamentally limits the time that these molecules can be kept in a single quantum state in a trap. To demonstrate and quantify this, we have monitored the optical pumping of electrostatically trapped OH and OD radicals by room-temperature blackbody radiation. Transfer of these molecules to rotationally excited states by blackbody radiation at 295 K limits the 1=e trapping time for OH and OD in the X 2 3=2 , v 00 0, J 00 3=2f state to 2.8 and 7.1 s, respectively. DOI: 10.1103/PhysRevLett.98.133001 PACS numbers: 33.80.Ps, 33.55.Be, 44.40.+a In his 1917 paper Einstein showed [1] that even in the absence of collisions the velocity distribution of a molecular gas takes on a Maxwellian distribution due to the momentum transfer that takes place in the absorption and emission of blackbody radiation. The absorbed and emitted photons optically pump the rotational and vibrational transitions, resulting in thermal distributions over the available states. The rotational temperature of the CN molecule in interstellar space [2], for example, is the result of optical pumping by the cosmic microwave background-radiation [3].The influence of blackbody radiation on atoms and molecules is in general small and it is rare that it can be observed directly in laboratory experiments. However, in a number of cases the interaction with blackbody radiation is experimentally observable and important. The first dynamical effects of blackbody radiation on the population of atomic levels were noticed when studying the lifetime of highly excited Rydberg states in atoms [4]. Atoms in these states can have dipole moments of thousands of Debye, and have sufficient spectral overlap with the spectrum of roomtemperature blackbody radiation. The excitation (and ionization) rates can be on the order of 1000 s ÿ1 , implying that the effect can already be observed on a s time scale.The excitation rates in ground state atoms and molecules are generally much lower, and therefore require a longer interaction time to be observed. Only with the development of ion traps, together with a sufficient reduction of collisional energy exchange (i.e., a good vacuum at room temperature), could the photodissociation of molecular ions and clusters by blackbody radiation be directly observed [5,6]. Ions in storage rings are also trapped long enough for the interaction with blackbody radiation to be noticeable [7].The effect of blackbody radiation on neutral molecules in a trap has until now been left experimentally unexplored, partly because the conditions to observe the effect were not met, and partly because the importance of this effect was not always realized. Polar molecules generally have strong vibrational and/or rotational transitions in the infrared region of the spectrum. As a result they can relatively easily be optically pumped by room-temperature blackbody radiation, and this fundamentally limits the time that these molecules can be kept in a single quantum state in ro...

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“…Sympathetic cooling has been successfully used to achieve Fermi degeneracy in 6 Li, 8 Bose-Einstein condensation in 41 K, 9 and for producing ultracold ions. [10][11][12] However, it has not yet been achieved for molecular systems, although there are theoretical proposals for experiments in which ultracold NH or ND 3 molecules are obtained by collisions with a bath of colder atoms such as Rb, Mg, or N. [13][14][15] The group at Imperial College London recently succeeded in producing samples of cold LiH molecules in the first rotationally excited state 16,17 using Stark deceleration. LiH is an attractive molecule for cooling, since it has large dipole moment and light mass, so that it can be controlled easily with fields.…”

Section: Ref 1)mentioning

confidence: 99%

Interaction between LiH molecule and Li atom from state-of-the-art electronic structure calculations

Skomorowski

Pawłowski

Korona

et al. 2011

The Journal of Chemical Physics

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State-of-the-art ab initio techniques have been applied to compute the potential energy surface for the lithium atom interacting with the lithium hydride molecule in the Born-Oppenheimer approximation. The interaction potential was obtained using a combination of the explicitly correlated unrestricted coupled-cluster method with single, double, and noniterative triple excitations [UCCSD(T)-F12] for the core-core and core-valence correlation and full configuration interaction for the valence-valence correlation. The potential energy surface has a global minimum 8743 cm −1 deep if the Li-H bond length is held fixed at the monomer equilibrium distance or 8825 cm −1 deep if it is allowed to vary. In order to evaluate the performance of the conventional CCSD(T) approach, calculations were carried out using correlation-consistent polarized valence X-tuple-zeta basis sets, with X ranging from 2 to 5, and a very large set of bond functions. Using simple twopoint extrapolations based on the single-power laws X −2 and X −3 for the orbital basis sets, we were able to reproduce the CCSD(T)-F12 results for the characteristic points of the potential with an error of 0.49% at worst. The contribution beyond the CCSD(T)-F12 model, obtained from full configuration interaction (FCI) calculations for the valence-valence correlation, was shown to be very small, and the error bars on the potential were estimated. At linear LiH-Li geometries the ground-state potential shows an avoided crossing with an ion-pair potential. The energy difference between the ground-state and excited-state potentials at the avoided crossing is only 94 cm −1 .Using both adiabatic and diabatic pictures we analyse the interaction between the two potential energy surfaces and its possible impact on the collisional dynamics. When the LiH bond is allowed to vary, a seam of conical intersections appears at C 2v geometries. At the linear LiH-Li geometry, the conical intersection is at a Li-H distance which is only slightly larger than the monomer equilibrium distance, but for nonlinear geometries it quickly shifts to Li-H distances that are well outside the classical turning points of the ground-state potential of LiH. This suggests that the conical intersection will have little impact on the dynamics of Li-LiH collisions at ultralow temperatures.Finally, the reaction channels for the exchange and insertion reactions are also analyzed, and found to be unimportant for the dynamics.There is proposal to produce ultracold LiH molecules by sympathetic cooling with Li [18]. However, sympathetic cooling can be successful only if the rate of elastic (thermalization) collisions is large compared to the rate of inelastic (deexcitation) collisions, which cause trap loss. The main objects of the present paper are to explore the interaction between Li atoms and LiH molecules, to understand the nature of the interaction between these two species, and to obtain a detailed and accurate potential energy surface for the Li-LiH system.The results of scattering calculations at ultralo...

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A supersonic beam of cold lithium hydride molecules

Cited by 21 publications

References 32 publications

Dynamics of thermal Casimir-Polder forces on polar molecules

Dynamics of thermal Casimir-Polder forces on polar molecules

Optical Pumping of Trapped Neutral Molecules by Blackbody Radiation

Interaction between LiH molecule and Li atom from state-of-the-art electronic structure calculations

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