Measuring Atom-Molecule Superposition States

 

R. Dumke1, J. D. Weinstein1, M. Johanning1, K. M. Jones2 and P. D. Lett1

 

1Atomic Physics Division, National Institute of Standards and Technology, Gaithersburg , MD 20899-8424

2Physics Department, Williams College, Williamstown, Massachusetts 01267

 

The formation of ultra cold molecules is currently one of the most active subjects in atomic and molecular physics. Recently spectacular progress in this field has been achieved by using adiabatic sweeps of a magnetic field over Feshbach resonances to produce quantum degenerate gases leading towards the observation of Bose Einstein Condensation of molecules. Using optical fields for the manipulation of matter waves leads to a wide range of observable quantum interference effects between atoms and molecules.

We have performed a type of Autler-Townes spectroscopy to investigate the coherence properties between free atoms and molecules. By driving photoassociation transitions with continuous-wave lasers, we state-selectively form excited-state molecules from ultra-cold magnetically trapped atoms. Using a second laser to drive transitions from the excited state to the triplet ground state we are able to achieve line splittings smaller than the natural line-width of the excited molecular state, which indicates that a dark coherent atom-molecule superposition state has been formed which is decoupled from the laser-field. The line width and population of this state is limited in our experiment by the temperature of the atoms.

We are currently constructing a new apparatus in which we will be able to produce a BEC by optical evaporation to produce lower temperature atomic samples.