Photoassociation of ultracold CsYb molecules and determination of interspecies scattering lengths

• Main Author: Guttridge, Alexander
• Published: Durham University 2018
• Subjects: 530
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.761456

This thesis reports the first measurements of the ground state binding energies of CsYb molecules and the scattering lengths of the Cs+Yb system. The knowledge gained from these measurements will be essential for devising the most efficient route for the creation of rovibrational ground state CsYb molecules. CsYb molecules in the rovibrational ground state possess both electric and magnetic dipole moments which opens up a wealth of applications in many areas of physics and chemistry. In addition, we present the setup of a crossed beam optical dipole trap and the investigation of precooling and loading of Yb into the dipole trap. Evaporative cooling in the dipole trap results in the reliable production of Bose-Einstein condensates with $4 x 10^{5}$ $^{174}$Yb atoms. We also describe the necessary changes required to cool fermionic $^{173}$Yb atoms and report the production of a six-component degenerate Fermi gas of $8 x 10^{4}$ $^{173}$Yb atoms with a temperature of 0.3~$T_{\rm F}$. As well as the ability to cool Yb to degeneracy, we present the production of Bose-Einstein condensates containing $5 x 10^{4}$ $^{133}$Cs atoms. Effective cooling of Cs is achieved using Degenerate Raman sideband cooling, which enables $6 x 10^{7}$ Cs atoms to be cooled to below $2 \, \mu$K and polarised in the $\ket{F=3, m_{F}=+3}$ state with 90~\% efficiency. Finally, we report the production of ultracold heteronuclear Cs$^*$Yb and CsYb molecules using one-photon and two-photon photoassociation respectively. For the electronically excited Cs$^*$Yb molecules we use trap-loss spectroscopy to detect molecular states below the Cs($^{2}P_{1/2}$) + Yb($^{1}S_{0}$) asymptote. For $^{133}$Cs$^{174}$Yb, we observe 13 rovibrational states with binding energies up to $\sim$500\,GHz. In addition, we produce ultracold fermionic $^{133}$Cs$^{173}$Yb and bosonic $^{133}$Cs$^{172}$Yb and $^{133}$Cs$^{170}$Yb molecules. From mass scaling, we determine the number of vibrational levels supported by the 2(1/2) excited-state potential to be 154 or 155.