Proposal for Zeeman slowing of Rb2 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.

Automated summary

We propose a theoretical approach for Zeeman slowing of a Rb-2 supersonic beam, utilizing transitions between rovibrational levels of the X-1 sigma(+)(g) electronic ground-state and the B-1 Pi(u) electronic excited state. By using optical transitions from v(X)(SIC)13, J(X)(SIC)13 to v(B)=0, including P (J(B)=J(X)-1) and Q (J(B)=J(X)) branches, we induce translational cooling. Monte-Carlo simulations show that the velocity of the molecules can be reduced from 500 m s(-1) to a few m s(-1) using a 1.2 m long Zeeman slower after scattering about 150 000 photons. Upon the completion of the slowing process, it is predicted that half of the molecules will be internally cooled in the v(X)=2, 3, J(X)=1 ground-state levels. Further optical pumping to the v(X)=0, J(X)=1 ground-state level could yield a molecular beam with cold translational, vibrational, and rotational degrees of freedom, making this approach potentially valuable in the cooling of various molecular species.