We report the production of ultracold heteronuclear
7Li85Rb molecules in excited electronic states by photoassociation (PA) of ultracold
7Li and
85Rb atoms. PA is performed in a dual-species
7Li-
85Rb magneto-optical trap (MOT) and the PA resonances are detected using trap loss spectroscopy. We identify several strong PA resonances below the Li (2
s 2S1/2) + Rb (5
p 2P3/2) asymptote and experimentally determine the long range
C6 dispersion coefficients. We find a molecule formation rate (
PLiRb) of 3.5 \ifmmode\times\else\texttimes\fi{} 10
7 s${}^{\ensuremath{-}1}$ and a PA rate coefficient (
KPA) of 1.3 \ifmmode\times\else\texttimes\fi{} 10${}^{\ensuremath{-}10}$ cm
3/s, the highest among heteronuclear bi-alkali-metal molecules. At large PA laser intensity we observe the saturation of the PA rate coefficient (
KPA) close to the theoretical value at the unitarity limit.
We report the production of ultracold 7 Li 85 Rb molecules by photoassociation (PA) below the Li (2 s 2 S 1/2 ) + Rb(5 p 2 P 1/2 ) asymptote. We perform PA spectroscopy in a dual-species 7 Li- 85 Rb magneto-optical trap (MOT) and detect the PA resonances using trap loss spectroscopy. We observe several strong PA resonances corresponding to the last few bound states, assign the lines and derive the long-range C 6 dispersion coefficients for the Li (2 s 2 S 1/2 ) + Rb(5 p 2 P 1/2 ) asymptote. We also report an excited-state molecule formation rate of and a PA rate coefficient of , which are both among the highest observed for heteronuclear bi-alkali molecules. These suggest that PA is a promising route for the creation of ultracold ground-state LiRb molecules.
Heteronuclear polar molecules have recently attracted enormous attention owing to their ground state having a large electric dipole moment. The long range anisotropic dipole-dipole interaction in such systems is the basis for a variety of applications including quantum computing, precision measurements, ultracold chemistry and quantum simulations. Heteronuclear bi-alkali molecules, only a small subset of polar molecules, have received special attention mainly because the constituent alkali atoms are easy to laser cool and can be relatively easily associated to form molecules at ultracold temperatures. Our choice, the LiRb molecule, is motivated by the relatively high dipole moment (4.1 Debye) of the LiRb molecule in its rovibronic ground state. In this thesis, we study the LiRb molecule using laser spectroscopy and report, for the first time, the production of ultracold LiRb molecules by photoassociation (PA). The LiRb molecule is the least studied among all bi-alkali molecules and the first spectroscopic measurements on hot vapor phase LiRb molecules were reported only in 2011. We describe these measurements and their significance in chapter 2, after a brief introduction to the field of ultracold polar molecules in chapter 1. In chapter 3, we discuss our apparatus for simultaneous cooling and trapping of Li and Rb atoms in a dual-species magneto-optical trap (MOT) and report the measurement of interspecies collision-induced losses. In chapter 4, we describe the production of ultracold LiRb molecules in excited electronic states by photoassociation (PA). We report the measurements of the C6 coefficients for the Li (2s 2S1/2) + Rb (5p 2P1/2) and the Li (2s 2S1/2) + Rb (5p 2P3/2) asymptotes. We find a molecule formation rate (PLiRb) as high as 3.5x107 s-1 and a PA rate coefficient (KPA) as high as 1.3x10-10 cm3/s, the highest among heteronuclear bi-alkali molecules. In chapter 5, we discuss results on two-photon PA and we conclude, in chapter 6, with a road roadmap of future experiments for the production and detection of ultracold LiRb molecules in their rovibronic ground state.
We report on the production of ultracold heteronuclear YbLi* molecules in a dual-species magneto-optical trap by photoassociation (PA). The formation of the electronically excited molecules close to dissociation was observed by trap loss spectroscopy. We find 4 rovibrational states within a range of
250GHz below the
Yb(1S0)+Li(2P1/2) asymptote and observe isotopic PA line shifts in mixtures of
6Li with
174Yb,
172Yb, and
176Yb. We also describe our theoretical ab initio calculation for the relevant electronic potentials and utilize it to analyze and identify the lines in the experimentally observed spectrum.
We report the formation of ultracold (7)Li(85)Rb molecules in the a(3)Σ(+) electronic state by photoassociation (PA) and their detection via resonantly enhanced multiphoton ionization (REMPI). With our dual-species Li and Rb magneto-optical trap apparatus, we detect PA resonances with binding energies up to ∼62 cm(-1) below the (7)Li 2s (2)S1/2 + (85)Rb 5p (2)P1/2 asymptote. In addition, we use REMPI spectroscopy to probe the a(3)Σ(+) state and excited electronic 3(3)Π and 4(3)Σ(+) states and identify a(3)Σ(+) (v″ = 7-13), 3(3)Π (vΠ' = 0-10), and 4(3)Σ(+) (vΣ' = 0-5) vibrational levels. Our line assignments agree well with ab initio calculations. These preliminary spectroscopic studies on previously unobserved electronic states are crucial to discovering transition pathways for transferring ultracold LiRb molecules created via PA to deeply bound rovibrational levels of the electronic ground state.
We have produced ultracold heteronuclear ${\text{YbRb}}^{\ensuremath{\ast}}$ molecules in a combined magneto-optical trap by photoassociation. The formation of electronically excited molecules close to the dissociation limit was observed by the trap loss spectroscopy in mixtures of
87Rb with
174Yb and
176Yb. The molecules could be prepared in well-defined rovibrational levels, allowing for an experimental determination of the long-range potential in the electronically excited state.