The photoassociative spectroscopy, photoassociative molecule formation, and trapping of ultracold 39K85Rb

D. Wang, J. Qi, M. F. Stone, O. Nikolayeva, B. Hattaway, S. D. Gensemer, H. Wang, W. T. Zemke, P. L. Gould, E. E. Eyler, W. C. Stwalley

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Abstract

We have observed the photoassociative spectra of colliding ultracold 39K and 85Rb atoms to produce KRb* in all eight bound electronic states correlating with the 39K (4s) + 85RL(Sp1/2 and 5p3/2) asymptotes. These electronically excited KRb* ultracold molecules are detected after their radiative decay to the metastable triplet (a3+) state and (in some cases) the singlet (X1+) ground state. The triplet (a3+) ultracold molecules are detected by two-photon ionization at 602.5 nm to form KRb+, followed by time-of-flight mass spectroscopy. We are able to assign a majority of the spectrum to three states (2(0+), 2(0-), 2(1)) in a lower triad of states with similar C6 values correlating to the K(4s) + Rb (Sp1/2) asymptote; and to five states in an upper triad of three states (3(0+), 3(0-), 3(1)) and a dyad of two states (4(1), 1(2)), with one set of similar C6 values within the upper triad and a different set of similar C6 values within the dyad. We are also able to make connection with the short-range spectra of Kasahara et al. [J. Chem. Phys. 111, 8857 (1999)], identifying three of our levels as v = 61, 62 and 63 of the 11Π ∼ 4(1) state they observed. We also argue that ultracold photoassociation to levels between the K(4s) + Rb (5p 3/2) and K(4s) + Rb (5p1/2) asymptotes may be weakly or strongly predissociated and therefore difficult to observe by ionization of a3+ (or X1+) molecules; we do know from Kasahara et al. that levels of the 11Π ∼ 4(1) and 21Π ∼ 5(1) states in the intra-asymptote region are predissociated. A small fraction (≤1/3) of the triplet (a3+) ultracold molecules formed are trapped in the weak magnetic field of our magneto-optical trap (MOT).

Original languageEnglish (US)
Pages (from-to)165-177
Number of pages13
JournalEuropean Physical Journal D
Volume31
Issue number2
DOIs
Publication statusPublished - Nov 1 2004

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All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics

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