We report the first observation of translationally cold ( approximately 90 &mgr;K) Rb2 molecules. They are produced in a magneto-optical trap in their triplet ground state. The detection is performed by selective mass spectroscopy after two-photon ionization into Rb+2, resonantly enhanced through the intermediate a (3)Sigma(+)(u)-->2 (3)Pi(g) molecular band. The two rubidium isotopes present very different types of behavior that are interpreted in terms of their respective collisional properties.

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We produce Bose-Einstein condensates of 162 Dy atoms employing an innovative technique based on a resonator-enhanced optical trap that allows efficient loading from the magneto-optical trap. We characterize the scattering properties of the ultracold atoms for magnetic fields between 6 and 30 G. In addition to the typical chaotic distribution of narrow Feshbach resonances in Lanthanides, we discover two rather isolated broad features at around 22 G and 27 G. A characterization using the complementary measurements of losses, thermalization, anisotropic expansion and molecular binding energy points towards resonances of predominant s-wave character. Such resonances will ease the investigation of quantum phenomena relying on the interplay between dipole and contact interactions. 34.50.Cx, 37.0.De, 67.85.Hj Dipolar atomic Bose-Einstein condensates (dBEC) are proving to be excellent platforms for the study of a range of quantum phenomena relying on the interplay between the anisotropic long-range dipole-dipole interaction and the isotropic contact one. Recent experiments with dBEC demonstrated the existence of an unexpected quantum liquid phase, emerging for attractive mean-field interactions and stabilized by quantum fluctuations [1][2][3][4], showed the possibility to study lattice physics beyond the standard Bose-Hubbard model [5], and revealed first signatures of peculiar roton excitations [6] and scissors oscillations [7]. All these observations rely on the large magnetic moment available in Lanthanides, and require a fine control of the relative strength of dipolar and contact interactions. However, so far only very narrow Feshbach resonances, with widths of the order of tens of mG, have been employed to this scope. In fact, the complex electronic structure of such atoms, responsible for their large magnetic dipole moment, also leads to a strong anisotropy of the van der Waals interaction, which gives rise to an extremely dense chaotic distribution of narrow Feshbach resonances [8,9]. Dysprosium is the most magnetic atom available, whose magnetic dipole moment of 9.93 µ B results in a dipolar length a dd 130 a 0 . In the ground state of 164 Dy, besides the chaotic spectrum, two very broad Feshbach resonances with ∆ 30 G have been observed and characterized [10]. Their practical use is however questionable, since the resonances poles are surrounded by many narrow resonances. The other bosonic isotope, 162 Dy, has been characterized only up to 6 G: only narrow resonances appear, with the largest width around 25 mG [11,12].In this work we report on the production of a dBEC of 162 Dy and on the exploration of the resonance spec- * lucioni@lens.unifi.it trum up to 30 G. The BEC is produced employing a large-volume optical trap enhanced by an in-vacuum optical resonator, which allows an efficient capture of atoms from the magneto-optical trap (MOT) using a low-power single-mode laser. This technique was so far used only with alkalis and Yb atoms [13,14]; the application to dipolar Lanthanides is particularly intere...

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We demonstrate high-contrast Electromagnetically Induced Absorption (EIA) bright resonances on the D 1 line of 39 K with characteristics comparable to those of the Electromagnetically Induced Transparency (EIT) dark resonances observed in the same conditions. EIA is produced by the interaction of a weak probe beam with the atomic ground state driven in a degenerate coherent superposition by either a co-or counterpropagating pump beam. We have obtained an order of magnitude increase of the EIA's contrast with respect to previous similar experiments, performed with other alkalis, without compromising its linewidth. Furthermore, we show that the magneto-optic resonances can be continuously tuned from EIT to EIA by changing the relative handedness of circular polarizations of pump and probe beams, or depending on whether they co-or counter-propagate. This opens new perspectives in the use of EIA in a broad range of physical domains and in a large wealth of potential applications in optics and photonics. Contrary to Coherent Population Trapping and Electromagnetically Induced Transparency (EIT) with their ultra-narrow linewidths [1][2][3][4][5][6][7][8], Electromagnetically Induced Absorption (EIA) has found limited applications, mainly due to its broader linewidth and significantly smaller contrast. Nonetheless, an increasing interest in EIA was recently generated in view of potential applications, such as enhancement of the group velocity of light [9] and photonic metamaterials [10].EIA linewidths of several tens of kiloHertz have been reported, either with bichromatic excitation of Zeeman sublevels[11] or in Hanle configuration [12][13][14]. Bi-chromatic Hanle configuration has been explored by using Rb D 1 and D 2 lines [15]. Low-contrast EIA, resulting from EIT on D 2 line, was reported. Higher contrast EIA has been observed in [16], although overlapped to large background, which could be detrimental for highly-selective applications. More recently, sub-kHz EIA resonances were observed in Rb [17] and Cs [18,19]. In both cases, however, the contrast was of only a few percents. A pump/probe scheme in Hanle configuration for high-contrast EIA was proposed in a buffered vapor cell [20]. To date, however, no experimental demonstration has been reported. Highcontrast EIA has been observed on the 87 Rb D 2 line by using a complex excitation scheme with three separate photonic fields [21], and was theoretically investigated in [22]. EIA was also observed in the Paschen-Back regime in a purely non-degenerate three-level ladder system in 87 Rb [23]. Furthermore, while Rb and Cs have been widely investigated, this is the first observation of EIA in K, confirming our preliminary results [24].In this Letter, we report on an alternative and simpler approach for large contrast EIA in Hanle configuration using a pump/probe excitation scheme. We have observed EIA resonance contrast exceeding 50% in thermal K vapor. In this case, hyperfine optical pumping, which accumulates atoms to levels non interacting with the light [25,26], ...

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