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Durham e-Theses
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Creation of ultracold RbCs molecules

KOPPINGER, MICHAEL,PETER (2014) Creation of ultracold RbCs molecules. Doctoral thesis, Durham University.

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This thesis reports the investigation of the scattering properties of a mixture of Rb and Cs and the formation of ultracold Feshbach molecules. The production of Feshbach molecules is a crucial step towards the production of ultracold polar molecules, which is of significant interest for a wide range of potential applications.

We have investigated the scattering properties of a mixture of $^{85}$Rb and $^{133}$Cs in their lowest spin channel in a magnetic field range from 0 to 700\,G. Furthermore, we explored the Feshbach spectrum of $^{85}$Rb alone in both, the $(f=2,m_f=-2)$ and $(2,+2)$ states up to a magnetic field of 1000\,G. Additionally a Feshbach resonance in a $(2,+2)+(3,+3)$ spin mixture was experimentally confirmed.

We associated Cs$_2$ Feshbach molecules using a Feshbach resonance at 19.9\,G. \mbox{$2.1(1) \times 10^4$} molecules with a temperature of $\sim60$\,nK were produced from a sample of $3.28(2) \times 10^5$ Cs atoms with a PSD of 0.20(1). Due to a magnetic field gradient, the molecules `bounce' at an avoided crossing between two states at 13.5\,G. This gradient field was also used to produce multiple molecular clouds from one atomic sample. A combination of both techniques led to a `collision' between two Cs$_2$ clouds.

Furthermore, we associated up to $\sim5000$ heteronuclear $^{87}$RbCs Feshbach molecules using an interspecies resonance at 197.1\,G. Confined in the dipole trap the molecules have a lifetime of 0.21(1)\,s. We have measured the magnetic moment of the molecules in different internal states in a magnetic field range from 181 to 185\,G.

Molecular loss spectroscopy on electronically excited states was performed to identify candidates for the intermediate state of a STIRAP transfer of the molecules into their rovibrational ground state. Subsequently, the binding energy of the rovibrational ground state was measured to be 3811.574(1)\,cm$^{-1}$, using two-photon spectroscopy.

Item Type:Thesis (Doctoral)
Award:Doctor of Philosophy
Keywords:Bose-Einstein condensate, Feshbach resonance, Ultracold molecules
Faculty and Department:Faculty of Science > Physics, Department of
Thesis Date:2014
Copyright:Copyright of this thesis is held by the author
Deposited On:09 Jul 2014 10:50

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