Proposal for Zeeman slowing of Rb2 molecules in a supersonic beam, inducing internal cooling

Abstract

Abstract We present a theoretical proposal on Zeeman slowing of a Rb2 supersonic beam, relying on transitions between rovibrational levels of the X 1 Σ g + electronic ground-state and the B 1 Π u electronic excited state. Translational cooling is induced by optical transitions from v X ⩽ 13 , J X ⩽ 13 to v B = 0 involving P ( J B = J X − 1 ) and Q ( J B = J X ) branches. This is achieved by shaping the spectrum of broadband laser sources, in addition to two single-frequency laser sources addressing the X 1 Σ g + ( v X = 2 , 3 , J X = 1 ) → B 1 Π u ( v B = 0 , J B = 1 ) transitions. Our Monte–Carlo simulations indicate that the velocity of the molecules can be slowed from 500 m s−1 down to a few m s−1 by a Zeeman slower with a 1.2 m length, after scattering about 150 000 photons. At the end of the slowing process, half of the molecules are internally cooled, predicted to be in the v X = 2 , 3 , J X = 1 ground-state levels. A final optical pumping step transferring the population to the v X = 0 , J X = 1 ground-state level could produce a molecular beam exiting the Zeeman slower which is cold in all the translational, vibrational, and rotational degrees of freedom. Such an approach could potentially be a great interest for cooling down a large class of molecular species.