Optical Pumping and Vibrational Cooling of Molecules

Abstract

The methods producing cold molecules from cold atoms tend to leave molecular ensembles with substantial residual internal energy. For instance, Cs 2 molecules initially formed via photoassociation of cold Cs atoms are in several vibrational levels, v, of the electronic ground state. Here we apply a broadband femtosecond laser that redistributes the vibrational population in the ground state via a few electronic excitation -spontaneous emission cycles. The laser pulses are shaped to remove the excitation frequency band of the v = 0 level, preventing re-excitation from that state. We observe a fast and efficient accumulation, ∼ 70% of the initially detected molecules, in the lowest vibrational level, v = 0, of the singlet electronic state. The validity of this incoherent depopulation pumping method is very general and opens exciting prospects for laser cooling and manipulation of molecules.

Formation of molecular oxygen in ultracoldO+OHcollisions

“…Very recently, formation of ground state molecules in the vibrational level v = 0 has been reported by different groups for homonuclear molecules such as Cs 2 [2], Rb 2 [3], as well as for heteronuclear polar molecules such as RbCs [4], KRb [5], and LiCs [7]. There has also been much progress in the measurement of rate coefficients of barrierless reactions involving alkali-metal atoms at cold and ultracold temperatures.…”

Quantum Control of the Spin-Orbit Interaction Using the Autler-Townes Effect

“…singlet and triplet) have been used as "gateways" or "windows" for accessing states with different spin character than the ground state [6][7][8][9]. Such perturbed levels have also been used as intermediate levels in the transfer of cold molecules formed at long range in the triplet a 3 Σ + state to deeply bound levels of the singlet X 1 Σ + ground state [10][11][12][13][14]. Thus, the ability to enhance the mixing of the spin character of singlet-triplet pairs of states could be used to improve the transfer rates in such schemes.…”

Direct photoassociative formation of ultracold KRb molecules in the lowest vibrational levels of the electronic ground state

“…However a pure sample of rovibrational ground state molecules is still achievable after the PA process by several possible methods. As discussed in [26], vibrational cooling of the sample is one option. For KRb molecules, the 2 1 Σ + − 1 3 Π complex can provide intermediate states for optical pumping of molecules in higher vibrational levels down to v ′′ = 0.…”