This thesis describes a suite of experimental tools and spectroscopic measurements performed on ultracold ⁶Li molecules. The aim is to create the necessary ingredients for the coherent transfer of the population of ultracold, weakly bound, Feshbach molecules of ⁶Li to deeply bound ro-vibrational levels, making the eventual creation of a Bose-Einstein condensate (BEC) of ground state lithium dimers a reality at the University of British Columbia. Some of the technological milestones include the development of a unique laser system consisting of two Ti:Sapphire lasers frequency stabilized to a femtosecond frequency comb as well as the demonstration of the first in Canada BEC of Feshbach molecules. To determine a suitable path for the coherent transfer using stimulated Raman adiabatic passage (STIRAP) we measure the binding energies of the vibrational levels v''=20-26 of the c(1³Ʃ+g) and v''=29-35 of the A(1¹Ʃ+u) excited states of lithium dimers by the photoassociation of a degenerate Fermi gas of 6Li atoms, achieving accuracy of 600 kHz. For each vibrational level of the triplet potential, we resolve the rotational structure using a Feshbach resonance to enhance the photoassociation rates from p-wave collisions. We also, for the first time, determine the spin-spin and spin-rotation interaction constants for this state. Finally, we are the first to demonstrate exotic dark states in quantum gases of fermionic lithium where atom-molecule coherence is produced between a deeply bound singlet (or triplet) molecular level and atomic pairs in a weakly interacting Fermi gas at zero gauss or in the BEC-BCS crossover regime (i.e. Feshbach molecules or BCS-like pairs). We observe an abrupt and unanticipated change of the classic EIT signature (Electromagnetically Induced Transparency) of the dark-state (i.e. the suppression of single photon absorption to the excited state) in the vicinity of the broad Feshbach resonance at 832.2 gauss potentially indicating new physics not previously considered.This thesis describes a suite of experimental tools and spectroscopic measurements performed on ultracold ⁶Li molecules. The aim is to create the necessary ingredients for the coherent transfer of the population of ultracold, weakly bound, Feshbach molecules of ⁶Li to deeply bound ro-vibrational levels, making the eventual creation of a Bose-Einstein condensate (BEC) of ground state lithium dimers a reality at the University of British Columbia. Some of the technological milestones include the development of a unique laser system consisting of two Ti:Sapphire lasers frequency stabilized to a femtosecond frequency comb as well as the demonstration of the first in Canada BEC of Feshbach molecules. To determine a suitable path for the coherent transfer using stimulated Raman adiabatic passage (STIRAP) we measure the binding energies of the vibrational levels v''=20-26 of the c(1³Ʃ+g) and v''=29-35 of the A(1¹Ʃ+u) excited states of lithium dimers by the photoassociation of a degenerate Fermi gas of 6Li atoms, achieving accuracy of 600 kHz. For each vibrational level of the triplet potential, we resolve the rotational structure using a Feshbach resonance to enhance the photoassociation rates from p-wave collisions. We also, for the first time, determine the spin-spin and spin-rotation interaction constants for this state. Finally, we are the first to demonstrate exotic dark states in quantum gases of fermionic lithium where atom-molecule coherence is produced between a deeply bound singlet (or triplet) molecular level and atomic pairs in a weakly interacting Fermi gas at zero gauss or in the BEC-BCS crossover regime (i.e. Feshbach molecules or BCS-like pairs). We observe an abrupt and unanticipated change of the classic EIT signature (Electromagnetically Induced Transparency) of the dark-state (i.e. the suppression of single photon absorption to the excited state) in the vicinity of the broad Feshbach resonance at 832.2 gauss potentially indicating new physics not previously considered.

Jan 1, 20151 citation

Photoassociation Spectroscopy: Determination of Parameters of Potentials of Diatomic Molecules

James Gary Eden, Henry Tran, V. S. Zuev

Journal of Russian Laser ResearchMar 1, 19981 citation

High-resolution photoassociation spectroscopy of the 6 Li 2 13Σg+ state

Mariusz Semczuk, Xuan Li, Will Gunton +6 more

We present experimental observations of seven vibrational levels, ${v}^{\ensuremath{'}}=20$--26, of the ${1}^{3}{\ensuremath{\Sigma}}_{g}^{+}$ excited state of Li ${}_{2}$ molecules by the photoassociation (PA) of a degenerate Fermi gas of ${}^{6}$ Li atoms. For each vibrational level, we resolve the rotational structure using a Feshbach resonance to enhance the PA rates from $p$ -wave collisions. We also determine the spin-spin and spin-rotation interaction constants for this state. The absolute uncertainty of our measurements is $\ifmmode\pm\else\textpm\fi{}0.00002$ cm${}^{\ensuremath{-}1}$ ($\ifmmode\pm\else\textpm\fi{}600$ kHz). We use this data to further refine an analytic potential for this state.We present experimental observations of seven vibrational levels, ${v}^{\ensuremath{'}}=20$--26, of the ${1}^{3}{\ensuremath{\Sigma}}_{g}^{+}$ excited state of Li${}_{2}$ molecules by the photoassociation (PA) of a degenerate Fermi gas of ${}^{6}$Li atoms. For each vibrational level, we resolve the rotational structure using a Feshbach resonance to enhance the PA rates from $p$-wave collisions. We also determine the spin-spin and spin-rotation interaction constants for this state. The absolute uncertainty of our measurements is $\ifmmode\pm\else\textpm\fi{}0.00002$ cm${}^{\ensuremath{-}1}$ ($\ifmmode\pm\else\textpm\fi{}600$ kHz). We use this data to further refine an analytic potential for this state.

arXiv:1309.6662Physical Review AMay 9, 201328 citations

We present experimental observations of seven vibrational levels, ${v}^{\ensuremath{'}}=20$--26, of the ${1}^{3}{\ensuremath{\Sigma}}_{g}^{+}$ excited state of Li

{}_{2}

molecules by the photoassociation (PA) of a degenerate Fermi gas of

{}^{6}

Li atoms. For each vibrational level, we resolve the rotational structure using a Feshbach resonance to enhance the PA rates from

p

-wave collisions. We also determine the spin-spin and spin-rotation interaction constants for this state. The absolute uncertainty of our measurements is $\ifmmode\pm\else\textpm\fi{}0.00002$ cm${}^{\ensuremath{-}1}$ ($\ifmmode\pm\else\textpm\fi{}600$ kHz). We use this data to further refine an analytic potential for this state.