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Two-photon pathway to ultracold ground state molecules of [superscript 23]Na [superscript 40]K

Jee Woo Park, Sebastian Will, Martin W. Zwierlein

Published Jul 1, 2015• 0 citations
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Abstract

We report on high-resolution spectroscopy of ultracold fermionic [superscript 23]Na[superscript 40]K Feshbach molecules, and identify a two-photon pathway to the rovibrational singlet ground state via a resonantly mixed B[superscript 1]Π ~ c[superscript 3]Σ[superscript +]intermediate state. Photoassociation in a [superscript 23]Na–[superscript 40]K atomic mixture and one-photon spectroscopy on [superscript 23]Na[superscript 40]K Feshbach molecules reveal about 20 vibrational levels of the electronically excited c[superscript 3]Σ[superscript +]state. Two of these levels are found to be strongly perturbed by nearby B[superscript 1]Π levels via spin–orbit coupling, resulting in additional lines of dominant singlet character in the perturbed complex B[superscript 1}Π |v = 4〉 ~ c[superscript 3]∑[superscript +] v = 25〉, or of resonantly mixed character in B[superscript 1}Π |v = 12〉 ~ c[superscript 3]∑[superscript +] v = 35〉. The dominantly singlet level is used to locate the absolute rovibrational singlet ground state X[superscript 1]∑[superscript +] |v = 0, J = 0〉 via Autler–Townes spectroscopy. We demonstrate coherent two-photon coupling via dark state spectroscopy between the predominantly triplet Feshbach molecular state and the singlet ground state. Its binding energy is measured to be 5212.0447(1) cm[superscript −1], a thousand-fold improvement in accuracy compared to previous determinations. In their absolute singlet ground state, [superscript 23]Na[superscript 40]K molecules are chemically stable under binary collisions and possess a large electric dipole moment of 2.72 Debye. Our work thus paves the way towards the creation of strongly dipolar Fermi gases of NaK molecules.

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Two-photon pathway to ultracold ground state molecules of23Na40K

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We report on high-resolution spectroscopy of ultracold fermionic 23 Na 40 K Feshbach molecules, and identify a two-photon pathway to the rovibrational singlet ground state via a resonantly mixed B 1 Π ∼ c 3 Σ + intermediate state.Photoassociation in a 23 Na-40 K atomic mixture and one-photon spectroscopy on 23 Na 40 K Feshbach molecules reveal about 20 vibrational levels of the electronically excited c 3 Σ + state.Two of these levels are found to be strongly perturbed by nearby B 1 Π levels via spinorbit coupling, resulting in additional lines of dominant singlet character in the perturbed complex. The dominantly singlet level is used to locate the absolute rovibrational singlet ground state v J X 0, 0via Autler-Townes spectroscopy.We demonstrate coherent two-photon coupling via dark state spectroscopy between the predominantly triplet Feshbach molecular state and the singlet ground state.Its binding energy is measured to be 5212.0447(1)cm -1 , a thousand-fold improvement in accuracy compared to previous determinations.In their absolute singlet ground state, 23 Na 40 K molecules are chemically stable under binary collisions and possess a large electric dipole moment of 2.72 Debye.Our work thus paves the way towards the creation of strongly dipolar Fermi gases of NaK molecules.

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Ultracold Dipolar Gas of Fermionic [superscript 23]Na[superscript 40]K Molecules in Their Absolute Ground State

Jee Woo Park, Sebastian Will, Martin W. Zwierlein

We report on the creation of an ultracold dipolar gas of fermionic [superscript 23]Na[superscript 40]Kmolecules in their absolute rovibrational and hyperfine ground state. Starting from weakly bound Feshbach molecules, we demonstrate hyperfine resolved two-photon transfer into the singlet X[superscript 1]Σ[superscript +]|v = 0,J = 0⟩ ground state, coherently bridging a binding energy difference of 0.65 eV via stimulated rapid adiabatic passage. The spin-polarized, nearly quantum degenerate molecular gas displays a lifetime longer than 2.5 s, highlighting NaK’s stability against two-body chemical reactions. A homogeneous electric field is applied to induce a dipole moment of up to 0.8 D. With these advances, the exploration of many-body physics with strongly dipolar Fermi gases of [superscript 23]Na[superscript 40]K molecules is within experimental reach.

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We report on the formation of ultracold weakly bound Feshbach molecules of [superscript 23]Na[superscript 40]K, the first fermionic molecule that is chemically stable in its absolute ground state. The lifetime of the nearly degenerate molecular gas exceeds 100 ms in the vicinity of the Feshbach resonance. The measured dependence of the molecular binding energy on the magnetic field demonstrates the open-channel character of the molecules over a wide field range and implies significant singlet admixture. This will enable efficient transfer into the singlet vibrational ground state, resulting in a stable molecular Fermi gas with strong dipolar interactions.

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Abstract We spectroscopically investigate a pathway for the conversion of 23Na39K Feshbach molecules into rovibronic ground state molecules via stimulated Raman adiabatic passage. Using photoassociation spectroscopy from the diatomic scattering threshold in the a 3Σ+ potential, we locate the resonantly mixed electronically excited intermediate states ∣ B 1 Π , v = 8 〉 and ∣ c 3 Σ + , v = 30 〉 which, due to their singlet–triplet admixture, serve as an ideal bridge between predominantly a 3Σ+ Feshbach molecules and pure X 1Σ+ ground state molecules. We investigate their hyperfine structure and present a simple model to determine the singlet–triplet coupling of these states. Using Autler–Townes spectroscopy, we locate the rovibronic ground state of the 23Na39K molecule ( ∣ X 1 Σ + , v = 0 , N = 0 〉 ) and the second rotationally excited state N = 2 to unambiguously identify the ground state. We also extract the effective transition dipole moment from the excited to the ground state. Our investigations result in a fully characterized scheme for the creation of ultracold bosonic 23Na39K ground state molecules.

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Ultracold Dipolar Gas of Fermionic Na 23 K 40 Molecules in Their Absolute Ground State

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We report the successful production of an ultracold sample of absolute ground-state ^{23}Na^{87}Rb molecules. Starting from weakly bound Feshbach molecules formed via magnetoassociation, the lowest rovibrational and hyperfine level of the electronic ground state is populated following a high-efficiency and high-resolution two-photon Raman process. The high-purity absolute ground-state samples have up to 8000 molecules and densities of over 10^{11} cm^{-3}. By measuring the Stark shifts induced by external electric fields, we determined the permanent electric dipole moment of the absolute ground-state ^{23}Na^{87}Rb and demonstrated the capability of inducing an effective dipole moment over 1 D. Bimolecular reaction between ground-state ^{23}Na^{87}Rb molecules is endothermic, but we still observed a rather fast decay of the molecular sample. Our results pave the way toward investigation of ultracold molecular collisions in a fully controlled manner and possibly to quantum gases of ultracold bosonic molecules with strong dipolar interactions.

arXiv:1602.03947•Physical Review Letters•May 19, 2016•369 citations
We report on high-resolution spectroscopy of ultracold fermionic [superscript 23]Na[superscript 40]K Feshbach molecules, and identify a two-photon pathway to the rovibrational singlet ground state via a resonantly mixed B[superscript 1]Π ~ c[superscript 3]Σ[superscript +]intermediate state. Photoassociation in a [superscript 23]Na–[superscript 40]K atomic mixture and one-photon spectroscopy on [superscript 23]Na[superscript 40]K Feshbach molecules reveal about 20 vibrational levels of the electronically excited c[superscript 3]Σ[superscript +]state. Two of these levels are found to be strongly perturbed by nearby B[superscript 1]Π levels via spin–orbit coupling, resulting in additional lines of dominant singlet character in the perturbed complex B[superscript 1}Π |v = 4〉 ~ c[superscript 3]∑[superscript +] v = 25〉, or of resonantly mixed character in B[superscript 1}Π |v = 12〉 ~ c[superscript 3]∑[superscript +] v = 35〉. The dominantly singlet level is used to locate the absolute rovibrational singlet ground state X[superscript 1]∑[superscript +] |v = 0, J = 0〉 via Autler–Townes spectroscopy. We demonstrate coherent two-photon coupling via dark state spectroscopy between the predominantly triplet Feshbach molecular state and the singlet ground state. Its binding energy is measured to be 5212.0447(1) cm[superscript −1], a thousand-fold improvement in accuracy compared to previous determinations. In their absolute singlet ground state, [superscript 23]Na[superscript 40]K molecules are chemically stable under binary collisions and possess a large electric dipole moment of 2.72 Debye. Our work thus paves the way towards the creation of strongly dipolar Fermi gases of NaK molecules.
We report on high-resolution spectroscopy of ultracold fermionic 23 Na 40 K Feshbach molecules, and identify a two-photon pathway to the rovibrational singlet ground state via a resonantly mixed B 1 Π ∼ c 3 Σ + intermediate state.Photoassociation in a 23 Na-40 K atomic mixture and one-photon spectroscopy on 23 Na 40 K Feshbach molecules reveal about 20 vibrational levels of the electronically excited c 3 Σ + state.Two of these levels are found to be strongly perturbed by nearby B 1 Π levels via spinorbit coupling, resulting in additional lines of dominant singlet character in the perturbed complex. The dominantly singlet level is used to locate the absolute rovibrational singlet ground state v J X 0, 0via Autler-Townes spectroscopy.We demonstrate coherent two-photon coupling via dark state spectroscopy between the predominantly triplet Feshbach molecular state and the singlet ground state.Its binding energy is measured to be 5212.0447(1)cm -1 , a thousand-fold improvement in accuracy compared to previous determinations.In their absolute singlet ground state, 23 Na 40 K molecules are chemically stable under binary collisions and possess a large electric dipole moment of 2.72 Debye.Our work thus paves the way towards the creation of strongly dipolar Fermi gases of NaK molecules.
We report on the creation of an ultracold dipolar gas of fermionic [superscript 23]Na[superscript 40]Kmolecules in their absolute rovibrational and hyperfine ground state. Starting from weakly bound Feshbach molecules, we demonstrate hyperfine resolved two-photon transfer into the singlet X[superscript 1]Σ[superscript +]|v = 0,J = 0⟩ ground state, coherently bridging a binding energy difference of 0.65 eV via stimulated rapid adiabatic passage. The spin-polarized, nearly quantum degenerate molecular gas displays a lifetime longer than 2.5 s, highlighting NaK’s stability against two-body chemical reactions. A homogeneous electric field is applied to induce a dipole moment of up to 0.8 D. With these advances, the exploration of many-body physics with strongly dipolar Fermi gases of [superscript 23]Na[superscript 40]K molecules is within experimental reach.
We report on the formation of ultracold weakly bound Feshbach molecules of [superscript 23]Na[superscript 40]K, the first fermionic molecule that is chemically stable in its absolute ground state. The lifetime of the nearly degenerate molecular gas exceeds 100 ms in the vicinity of the Feshbach resonance. The measured dependence of the molecular binding energy on the magnetic field demonstrates the open-channel character of the molecules over a wide field range and implies significant singlet admixture. This will enable efficient transfer into the singlet vibrational ground state, resulting in a stable molecular Fermi gas with strong dipolar interactions.
Abstract We spectroscopically investigate a pathway for the conversion of 23Na39K Feshbach molecules into rovibronic ground state molecules via stimulated Raman adiabatic passage. Using photoassociation spectroscopy from the diatomic scattering threshold in the a 3Σ+ potential, we locate the resonantly mixed electronically excited intermediate states ∣ B 1 Π , v = 8 〉 and ∣ c 3 Σ + , v = 30 〉 which, due to their singlet–triplet admixture, serve as an ideal bridge between predominantly a 3Σ+ Feshbach molecules and pure X 1Σ+ ground state molecules. We investigate their hyperfine structure and present a simple model to determine the singlet–triplet coupling of these states. Using Autler–Townes spectroscopy, we locate the rovibronic ground state of the 23Na39K molecule ( ∣ X 1 Σ + , v = 0 , N = 0 〉 ) and the second rotationally excited state N = 2 to unambiguously identify the ground state. We also extract the effective transition dipole moment from the excited to the ground state. Our investigations result in a fully characterized scheme for the creation of ultracold bosonic 23Na39K ground state molecules.
We report on the creation of an ultracold dipolar gas of fermionic 23Na40 K molecules in their absolute rovibrational and hyperfine ground state. Starting from weakly bound Feshbach molecules, we demonstrate hyperfine resolved two-photon transfer into the singlet X 1Σ+|v=0,J=0⟩ ground state, coherently bridging a binding energy difference of 0.65 eV via stimulated rapid adiabatic passage. The spin-polarized, nearly quantum degenerate molecular gas displays a lifetime longer than 2.5 s, highlighting NaK's stability against two-body chemical reactions. A homogeneous electric field is applied to induce a dipole moment of up to 0.8 D. With these advances, the exploration of many-body physics with strongly dipolar Fermi gases of 23Na40K molecules is within experimental reach.
We report the successful production of an ultracold sample of absolute ground-state ^{23}Na^{87}Rb molecules. Starting from weakly bound Feshbach molecules formed via magnetoassociation, the lowest rovibrational and hyperfine level of the electronic ground state is populated following a high-efficiency and high-resolution two-photon Raman process. The high-purity absolute ground-state samples have up to 8000 molecules and densities of over 10^{11} cm^{-3}. By measuring the Stark shifts induced by external electric fields, we determined the permanent electric dipole moment of the absolute ground-state ^{23}Na^{87}Rb and demonstrated the capability of inducing an effective dipole moment over 1 D. Bimolecular reaction between ground-state ^{23}Na^{87}Rb molecules is endothermic, but we still observed a rather fast decay of the molecular sample. Our results pave the way toward investigation of ultracold molecular collisions in a fully controlled manner and possibly to quantum gases of ultracold bosonic molecules with strong dipolar interactions.