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Register a new userPhotoassociation to the 2(1)Sigma(g)(+) state in ultracold 85Rb2 in the presence of a shape resonance
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We report the first observation of photoassociation to the 2(1)Sigma(g)(+) state of 85Rb2 . We have observed two vibrational levels (v=98, 99) below the 5s1/2+5p1/2 atomic limit and eleven vibrational levels (v=102-112) above it. The photoassociation---and subsequent spontaneous emission---occur predominantly between 15 and 20 Bohr in a region of internuclear distance best described as a transition between Hunds case (a) and Hunds case (c) coupling. The presence of a g-wave shape resonance in the collision of two ground-state atoms affects the photoassociation rate and lineshape of the J= 3 and 5 rotational levels.
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We report on the anomalously high line strength of a single rotational level in the ultracold photoassociation of two 85Rb atoms to form 85Rb2. The v = 111, J = 5 level belongs to the Hunds case (c) 2 (0g+) state, which correlates to the Hunds case (a) 2 1 Sigma g+ state. Its strength is caused by coupling with a very near-resonant long-range state. The long-range component is the energetically degenerate v = 155, J = 5 level of the case (c) 2 (1g)$ state, correlating to the case (a) 1 1 Pi g state. The line strength is enhanced by an order of magnitude through this coupling, relative to nearby vibrational levels and even to nearby rotational levels of the same vibrational level. This enhancement is in addition to the enhancement seen in all J = 3 and 5 levels of the 2 (0g+) state due to an l = 4 shape resonance in the a 3 Sigma u+ state continuum, which alters the distribution of levels formed by photoassociation.
We report on measurements of the binding energies of several weakly bound vibrational states of the paramagnetic $^{174}$Yb$^{6}$Li molecule in the electronic ground state using two-photon spectroscopy in an ultracold atomic mixture confined in an optical dipole trap. We theoretically analyze the experimental spectrum to obtain an accurate description of the long-range potential of the ground state molecule. Based on the measured binding energies, we arrive at an improved value of the interspecies $s$-wave scattering length $a_{s0}=30$ $a_0$. Employing coherent two-photon spectroscopy we also observe the creation of dark atom-molecule superposition states in the heteronuclear Yb-Li system. This work is an important step towards the efficient production of ultracold YbLi molecules via association from an ultracold atomic mixture.
We present experimental observations of seven vibrational levels $v=20-26$ of the $1^{3}Sigma_{g}^{+}$ excited state of Li$_2$ molecules by the photoassociation (PA) of a degenerate Fermi gas of $^6$Li atoms. For each vibrational level, we resolve the rotational structure using a Feshbach resonance to enhance the PA rates from p-wave collisions. We also, for the first time, determine the spin-spin and spin-rotation interaction constants for this state. The absolute uncertainty of our measurements is $pm 0.00002$ cm$^{-1}$ ($pm 600$ kHz). We use these new data to further refine an analytic potential for this state.
We study the time-resolved photoassociation of ultracold sodium in an optical dipole trap. The photoassociation laser excites pairs of atoms to molecular states of large total angular momentum at high intensities (above 20 kW/cm$^{2}$). Such transitions are generally suppressed at ultracold temperatures by the centrifugal barriers for high partial waves. Time-resolved ionization measurements reveal that the atoms are accelerated by the dipole potential of the photoassociation beam. We change the collision energy by varying the potential depth, and observe a strong variation of the photoassociation rate. These results demonstrate the important role of light forces in cw photoassociation at high intensities.
We perform photoassociation spectroscopy in an ultracold $^{23}$Na-$^6$Li mixture to study the $c^3Sigma^+$ excited triplet molecular potential. We observe 50 vibrational states and their substructure to an accuracy of 20 MHz, and provide line strength data from photoassociation loss measurements. An analysis of the vibrational line positions using near-dissociation expansions and a full potential fit is presented. This is the first observation of the $c^3Sigma^+$ potential, as well as photoassociation in the NaLi system.
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