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Physical Review Research

High resolution photoassociation spectroscopy of the excited c3Σ1+ potential of Na23Cs133

Lewis R. B. Picard, Jessie T. Zhang, William B. Cairncross, Kenneth Wang, Gabriel E. Patenotte, Annie Jihyun Park, Yichao Yu, Lee R. Liu, Jonathan D. Hood, Rosario González‐Férez, Kang-Kuen Ni

Published Jun 5, 2023• 11 citations
Publisher

Abstract

We report on photoassociation spectroscopy probing the ${c}^{3}{\mathrm{\ensuremath{\Sigma}}}_{1}^{+}$ potential of the bialkali NaCs molecule, identifying 11 vibrational lines between ${v}^{\ensuremath{'}}=0$ and ${v}^{\ensuremath{'}}=25$ of the excited ${c}^{3}{\mathrm{\ensuremath{\Sigma}}}_{1}^{+}$ potential and fitting their rotational and hyperfine structure. The observed lines are assigned by fitting to an effective Hamiltonian model of the excited-state structure with rotational and hyperfine constants as free parameters. We discuss unexpected broadening of select vibrational lines and its possible link to strong spin-orbit coupling of the ${c}^{3}{\mathrm{\ensuremath{\Sigma}}}_{1}^{+}$ potential with the nearby ${b}^{3}{\mathrm{\ensuremath{\Pi}}}_{1}$ and ${B}^{1}{\mathrm{\ensuremath{\Pi}}}_{1}$ manifolds. Finally, we report use of the ${v}^{\ensuremath{'}}=22$ line as an intermediate state for two-photon transfer of weakly bound Feshbach molecules to the rovibrational ground state of the ${X}^{1}{\mathrm{\ensuremath{\Sigma}}}^{+}$ manifold.

DOI
10.1103/physrevresearch.5.023149

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We report on photoassociation spectroscopy probing the c3\ensuremathΣ1+{c}^{3}{\mathrm{\ensuremath{\Sigma}}}_{1}^{+}c3\ensuremathΣ1+​ potential of the bialkali NaCs molecule, identifying 11 vibrational lines between v\ensuremath′=0{v}^{\ensuremath{'}}=0v\ensuremath′=0 and v\ensuremath′=25{v}^{\ensuremath{'}}=25v\ensuremath′=25 of the excited c3\ensuremathΣ1+{c}^{3}{\mathrm{\ensuremath{\Sigma}}}_{1}^{+}c3\ensuremathΣ1+​ potential and fitting their rotational and hyperfine structure. The observed lines are assigned by fitting to an effective Hamiltonian model of the excited-state structure with rotational and hyperfine constants as free parameters. We discuss unexpected broadening of select vibrational lines and its possible link to strong spin-orbit coupling of the c3\ensuremathΣ1+{c}^{3}{\mathrm{\ensuremath{\Sigma}}}_{1}^{+}c3\ensuremathΣ1+​ potential with the nearby b3\ensuremathΠ1{b}^{3}{\mathrm{\ensuremath{\Pi}}}_{1}b3\ensuremathΠ1​ and B1\ensuremathΠ1{B}^{1}{\mathrm{\ensuremath{\Pi}}}_{1}B1\ensuremathΠ1​ manifolds. Finally, we report use of the v\ensuremath′=22{v}^{\ensuremath{'}}=22v\ensuremath′=22 line as an intermediate state for two-photon transfer of weakly bound Feshbach molecules to the rovibrational ground state of the X1\ensuremathΣ+{X}^{1}{\mathrm{\ensuremath{\Sigma}}}^{+}X1\ensuremathΣ+ manifold.
High resolution photoassociation spectroscopy of the excited c3Σ1+c^3Σ_{1}^+c3Σ1+​ potential of 23^{23}23Na133^{133}133Cs
We report on photoassociation spectroscopy probing the c3Σ1+c^3Σ_{1}^+c3Σ1+​ potential of the bi-alkali NaCs molecule, identifying eleven vibrational lines between v′=0v' = 0v′=0 and v′=25v' = 25v′=25 of the excited c3Σ1+c^3Σ_{1}^+c3Σ1+​ potential, and resolving their rotational and hyperfine structure. The observed lines are assigned by fitting to an effective Hamiltonian model of the excited state structure with rotational and hyperfine constants as free parameters. We discuss unexpected broadening of select vibrational lines, and its possible link to strong spin-orbit coupling of the c3Σ1+c^3Σ_{1}^+c3Σ1+​ potential with the nearby b3Π1b^3Π_1b3Π1​ and B1Π1B^1Π_1B1Π1​ manifolds. Finally we report use of the v′=22v' = 22v′=22 line as an intermediate state for two-photon transfer of weakly bound Feshbach molecules to the rovibrational ground state of the X1Σ+X^1Σ^+X1Σ+ manifold.
We spectroscopically investigate the hyperfine, rotational, and Zeeman structure of the vibrational levels ${v}^{\ensuremath{'}}=0,7,13$ within the electronically excited $c{\phantom{\rule{0.222222em}{0ex}}}^{3}{\mathrm{\ensuremath{\Sigma}}}_{g}{}^{+}$ state of 87Rb2^{87}\mathrm{Rb}_{2}87Rb2​ for magnetic fields of up to 1000G1000\phantom{\rule{0.28em}{0ex}}\text{G}1000G. As spectroscopic methods we use short-range photoassociation of ultracold Rb atoms as well as photoexcitation of ultracold molecules which have been previously prepared in several well-defined quantum states of the $a{\phantom{\rule{0.222222em}{0ex}}}^{3}\mathrm{\ensuremath{\Sigma}}{}_{u}^{+}$ potential. As a by-product, we present optical two-photon transfer of weakly bound Feshbach molecules into $a{\phantom{\rule{0.222222em}{0ex}}}^{3}\mathrm{\ensuremath{\Sigma}}{}_{u}^{+}$, v=0v=0v=0 levels featuring different nuclear spin quantum numbers. A simple model reproduces well the molecular level structures of the $c{\phantom{\rule{0.222222em}{0ex}}}^{3}{\mathrm{\ensuremath{\Sigma}}}_{g}{}^{+}$ vibrational states and provides a consistent assignment of the measured resonance lines. Furthermore, the model can be used to predict the relative transition strengths of the lines. From fits to the data we extract for each vibrational level the rotational constant, the effective spin-spin interaction constant, as well as the Fermi contact parameter and the anisotropic hyperfine constant. In an alternative approach, we perform coupled-channel calculations where we fit the relevant potential energy curves, spin-orbit interactions, and hyperfine functions. The calculations reproduce the measured hyperfine level term frequencies with an average uncertainty of $\ifmmode\pm\else\textpm\fi{}9\phantom{\rule{0.28em}{0ex}}\mathrm{MHz}$, similar as for the simple model. From these fits we obtain a section of the potential energy curve for the $c{\phantom{\rule{0.222222em}{0ex}}}^{3}{\mathrm{\ensuremath{\Sigma}}}_{g}{}^{+}$ state which can be used for predicting the level structure for the vibrational manifold ${v}^{\ensuremath{'}}=0$ to 13 of this electronic state.
Abstract We present a study of two-photon pathways for the transfer of NaCs molecules to their rovibrational ground state. Starting from NaCs Feshbach molecules, we perform bound-bound excited state spectroscopy in the wavelength range from 900 nm to 940 nm, covering more than 30 vibrational states of the c 3 Σ + , b 3 Π , and B 1 Π electronic states. Analyzing the rotational substructure, we identify the highly mixed c 3 Σ 1 + | v = 22 ⟩ ∼ b 3 Π 1 | v = 54 ⟩ state as an efficient bridge for stimulated Raman adiabatic passage. We demonstrate transfer into the NaCs ground state with an efficiency of up to 88(4)%. Highly efficient transfer is critical for the realization of many-body quantum phases of strongly dipolar NaCs molecules and high fidelity detection of single molecules, for example, in spin physics experiments in optical lattices and quantum information experiments in optical tweezer arrays.
We have performed a type of Autler–Townes spectroscopy to locate a number of rovibrational-hyperfine levels of the a 3Σu+ potential, the lowest triplet potential of the Na2 dimer. The spectroscopy starts with the photoassociation of ultracold atoms in a magneto-optical trap. We have measured the binding energies of over 100 individual states spanning the vibrational levels v=8–15 of this potential (binding energies up to 27 cm−1). We obtain a typical accuracy of 15 MHz and a typical resolution of 20 MHz, improving on the 10 GHz accuracy and 30 GHz resolution previously available for the vibrational states v<12. Vibrational, rotational, and hyperfine structures are resolved. Additionally, we have been able to resolve the magnetic electron–electron spin–spin dipole splitting of a number of these hyperfine levels. The measured rotational and hyperfine structures show good agreement with theoretical calculations. An analysis of the remaining discrepancies indicates where possible refinements to the potentials can be made. We also observe evidence for the presence of second-order spin–orbit coupling.
We present experimental observations of seven vibrational levels, ${v}^{\ensuremath{'}}=20$--26, of the ${1}^{3}{\ensuremath{\Sigma}}_{g}^{+}$ excited state of Li2{}_{2}2​ molecules by the photoassociation (PA) of a degenerate Fermi gas of 6{}^{6}6Li atoms. For each vibrational level, we resolve the rotational structure using a Feshbach resonance to enhance the PA rates from ppp-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 report a detailed molecular spectroscopy study of the lowest excited electronic states of 23Na87Rb^{23}\mathrm{Na}\phantom{\rule{0.16em}{0ex}}^{87}\mathrm{Rb}23Na87Rb for producing ultracold 23Na87Rb^{23}\mathrm{Na}\phantom{\rule{0.16em}{0ex}}^{87}\mathrm{Rb}23Na87Rb molecules in the electronic, rovibrational, and hyperfine ground state. Starting from weakly bound Feshbach molecules, a series of vibrational levels of the $A{\phantom{\rule{0.16em}{0ex}}}^{1}{\mathrm{\ensuremath{\Sigma}}}^{+}\text{\ensuremath{-}}b{\phantom{\rule{0.16em}{0ex}}}^{3}\mathrm{\ensuremath{\Pi}}$ coupled excited states is investigated. After resolving, modeling, and interpreting the hyperfine structure of several lines, we successfully identify a long-lived level resulting from the accidental hyperfine coupling between the 0+{0}^{+}0+ and ${0}^{\ensuremath{-}}$ components of the $b{\phantom{\rule{0.16em}{0ex}}}^{3}\mathrm{\ensuremath{\Pi}}$ state, satisfying all the requirements for the population transfer toward the lowest rovibrational level of the $X{\phantom{\rule{0.16em}{0ex}}}^{1}{\mathrm{\ensuremath{\Sigma}}}^{+}$ state. Using two-photon spectroscopy, its binding energy is measured to be 4977.308(3) ${\mathrm{cm}}^{\ensuremath{-}1}$. We calibrate all the transition strengths carefully and also demonstrate Raman transfer of Feshbach molecules to the absolute ground state.