Proposal for Zeeman slowing of Rb-2 molecules in a supersonic beam, inducing internal cooling

We present a theoretical proposal on Zeeman slowing of a Rb-2 supersonic beam, relying on transitions between rovibrational levels of the X-1 sigma(+)(g) electronic ground-state and the B-1 Pi(u) electronic excited state. Translational cooling is induced by optical transitions from v(X) (SIC) 13, J(X )(SIC) 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 sigma(+)(g) (v(X) = 2, 3, J(X) = 1) -> B-1 Pi(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.