Determination of the calcium ground state scattering length  by photoassociation spectroscopy at large detunings

Vogt, Felix; Grain, Ch.; Nazarova, T.; Sterr, U.; Riehle, F.; Lisdat, Christian; Tiemann, E.

doi:10.1140/epjd/e2007-00175-8

Cited by 23 publications

(29 citation statements)

References 20 publications

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“…From the temporal evolution of the expansion we can estimate the chemical potential to be µ/k B = 55 nK, assuming that the condensate can be treated in the Thomas- . From this we estimate the scattering length of a ≈ 440 a 0 which is in good agreement with our previously measured value of 340 a 0 < a < 700 a 0 , obtained from photoassociation measurements [9].…”

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confidence: 90%

“…This also ensures efficient loading of the atoms from the MOT into the dipole trap. As 40 Ca has a large scattering length a of 340 a 0 < a < 700 a 0 (here a 0 ≈ 53 pm denotes the Bohr radius) [9] and with it a large three-body loss coefficient, a large volume single-beam optical trap is used for initial cooling. During evaporation the trap is transformed to a crossed dipole trap to maintain high trap frequencies.…”

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Bose-Einstein Condensation of Alkaline Earth Atoms:Ca40

et al. 2009

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We have achieved Bose-Einstein condensation of 40 Ca, the first for an alkaline earth element. The influence of elastic and inelastic collisions associated with the large ground-state s-wave scattering length of 40 Ca was measured. From these findings, an optimized loading and cooling scheme was developed that allowed us to condense about 2·10 4 atoms after laser cooling in a two-stage magnetooptical trap and subsequent forced evaporation in a crossed dipole trap within less than 3 s. The condensation of an alkaline earth element opens novel opportunities for precision measurements on the narrow intercombination lines as well as investigations of molecular states at the 1 S-3 P asymptotes.PACS numbers: 03.75.Hh, 67.85.HjThe first Bose-Einstein condensate (BEC) of a dilute quantum gas in 1995 has opened completely new avenues in physics. In subsequent years this quantum degenerate state could be reached with different species (for a recent list of references see, e. g., [1]). By far most research has been performed on alkali atomic and molecular BECs apart from hydrogen, metastable helium, chromium, and ytterbium. So far, no member of the alkaline earth elements could be brought to quantum degeneracy despite considerable effort [2,3]. The alkaline earth elements have unique properties, e. g., their narrow intercombination transitions or their ground state without a magnetic moment. Due to the non-degenerate ground state in 40 Ca and in the other alkaline earth elements, the associated simpler molecule structure allows for more accurate investigations of collisions [4,5]. Moreover, the vanishing magnetic moment in the ground and excited state will allow for novel applications in atom interferometry not hampered by phase shifts due to magnetic fields. Calcium has a particularly large ground state scattering length that not only made it interesting but also difficult to realize a BEC.Calcium (like the other alkaline earth elements) shares these properties with ytterbium which has a similar electronic structure [6] but has a five hundred-fold larger line width of the 1 S 0 -3 P 1 intercombination transition. This 370 Hz line width at 657 nm made calcium for some time the optical frequency standard with the lowest uncertainty in the visible [7]. Both technologies, optical frequency metrology and the generation of a BEC, can now be combined for novel applications.In this letter we report on the preparation of a 40 Ca BEC. Starting point for our experiment is a magnetooptical trap (MOT) on the 1 S 0 -1 P 1 transition in the singlet system. The vanishing ground-state magnetic moment prevents sub-Doppler cooling of 40 Ca in a MOT. To cool the atoms further we use a second MOT stage on the narrow intercombination line 1 S 0 -3 P 1 allowing for temperatures in the MOT as low as 15 µK. For efficient cooling we increase the scattering rate of this transition by quenching the upper state [8]. During both MOT stages an optical dipole trap is overlapped with the MOT. In order not to interfere with the narrow line cooling we choo...

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Bose-Einstein Condensation of Alkaline Earth Atoms:Ca40

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“…This variety is directly connected with the quantum defect in the ground electronic state which is dependent on reduced mass and scattering length of the colliding species. This sensitivity of the rotational structure of photoassociation lines can help in the determination or verification of the scattering length, as it was recently done in case of calcium by Vogt et al [39].…”

Section: Isotopic Variation Of Photoassociation Spectramentioning

confidence: 79%

Line shapes of optical Feshbach resonances near the intercombination transition of bosonic ytterbium

Borkowski¹,

Ciuryło²,

Julienne

et al. 2009

Phys. Rev. A

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The properties of bosonic Ytterbium photoassociation spectra near the intercombination transition 1 S0-3 P1 are studied theoretically at ultra low temperatures. We demonstrate how the shapes and intensities of rotational components of optical Feshbach resonances are affected by mass tuning of the scattering properties of the two colliding ground state atoms. Particular attention is given to the relationship between the magnitude of the scattering length and the occurrence of shape resonances in higher partial waves of the van der Waals system. We develop a mass scaled model of the excited state potential that represents the experimental data for different isotopes. The shape of the rotational photoassociation spectrum for various bosonic Yb isotopes can be qualitatively different.

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“…Based on these detailed spectroscopic data, an interval of the scattering length for 40 Ca is determined to be 340-700 a 0 [28]. In the 40 Ca BEC experiment, a scattering length of a ≈ 440 a 0 was estimated from a measurement of the chemical potential [6], without quoting an uncertainty.…”

Section: A Calciummentioning

confidence: 99%

Scattering lengths of calcium and barium isotopes

2011

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We have calculated the s-wave scattering length of all the even isotopes of calcium (Ca) and barium (Ba) in order to investigate the prospect of Bose-Einstein condensation (BEC). For Ca we have used an accurate molecular potential based on detailed spectroscopic data. Our calculations show that Ca does not provide other isotopes alternative to the recently Bose condensed 40 Ca that suffers strong losses because of a very large scattering length. For Ba we show by using a model potential that the even isotopes cover a broad range of scattering lengths, opening the possibility of BEC for at least one of the isotopes.

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Determination of the calcium ground state scattering length by photoassociation spectroscopy at large detunings

Cited by 23 publications

References 20 publications

Bose-Einstein Condensation of Alkaline Earth Atoms:Ca40

Bose-Einstein Condensation of Alkaline Earth Atoms:Ca40

Line shapes of optical Feshbach resonances near the intercombination transition of bosonic ytterbium

Scattering lengths of calcium and barium isotopes

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