Eur. Phys. J. D 31, 165-177 (2004)
https://doi.org/10.1140/epjd/e2004-00162-7

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

¹ Department of Physics, University of Connecticut, 2152 Hillside Road, Storrs, CT 06269-3046, USA
² Department of Physics, University of Latvia, 19 Rainis Boulevard, Riga 15986, Latvia
³ Department of Physics, University of Amsterdam, P.O. Box 94604, 1090 GP, Amsterdam, The Netherlands
⁴ Electronics and Photonics Laboratory, The Aerospace Corporation, M2-253, 2350 East El Segundo Boulevard, El Segundo, CA 90245-4691, USA
⁵ Department of Chemistry, Wartburg College, Waverly, IA 50677, USA

Corresponding author: ^a w.stwalley@uconn.edu

Received: 22 September 2004
Published online: 23 November 2004

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) + ⁸⁵Rb(5 and 5 asymptotes. These electronically excited KRb* ultracold molecules are detected after their radiative decay to the metastable triplet (a state and (in some cases) the singlet (X ground state. The triplet (a 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([see full textsee full textsee full textsee full textsee full textsee full textsee full text])) in a lower triad of states with similar C₆ values correlating to the K(4s) + Rb (5 asymptote; and to five states in an upper triad of three states (3(0, 3(0, 3([see full textsee full textsee full textsee full textsee full textsee full textsee full text])) and a dyad of two states (4([see full textsee full textsee full textsee full textsee full textsee full textsee full text]), 1([see full textsee full textsee full textsee full textsee full textsee full textsee full text])), 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 1 4([see full textsee full textsee full textsee full textsee full textsee full textsee full text]) state they observed. We also argue that ultracold photoassociation to levels between the K(4s) + Rb (5 and K(4s) + Rb (5 asymptotes may be weakly or strongly predissociated and therefore difficult to observe by ionization of a (or X molecules; we do know from Kasahara et al. that levels of the 1 4([see full textsee full textsee full textsee full textsee full textsee full textsee full text]) and 2 5([see full textsee full textsee full textsee full textsee full textsee full textsee full text]) states in the intra-asymptote region are predissociated. A small fraction (1/3) of the triplet (a ultracold molecules formed are trapped in the weak magnetic field of our magneto-optical trap (MOT).