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Anthony C. Legon - One of the best experts on this subject based on the ideXlab platform.
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a two force constant model for complexes b m x b is a lewis base and mx is any Diatomic Molecule intermolecular stretching force constants from centrifugal distortion constants dj or δj
Journal of Chemical Physics, 2016Co-Authors: Dror M Bittner, Nicholas R Walker, Anthony C. LegonAbstract:A two force-constant model is proposed for complexes of the type B⋯MX, in which B is a simple Lewis base of at least C2v symmetry and MX is any Diatomic Molecule lying along a Cn axis (n ≥ 2) of B. The model assumes a rigid subunit B and that force constants beyond quadratic are negligible. It leads to expressions that allow, in principle, the determination of three quadratic force constants F11, F12, and F22 associated with the r(B⋯M) = r2 and r(M–X) = r1 internal coordinates from the equilibrium centrifugal distortion constants DJe or ΔJe, the equilibrium principal axis coordinates a1 and a2, and equilibrium principal moments of inertia. The model can be applied generally to complexes containing different types of intermolecular bond. For example, the intermolecular bond of B⋯MX can be a hydrogen bond if MX is a hydrogen halide, a halogen-bond if MX is a dihalogen Molecule, or a stronger, coinage-metal bond if MX is a coinage metal halide. The equations were tested for BrCN, for which accurate equilibri...
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a two force constant model for complexes b m x b is a lewis base and mx is any Diatomic Molecule intermolecular stretching force constants from centrifugal distortion constants dj or δj
Journal of Chemical Physics, 2016Co-Authors: Dror M Bittner, Nicholas R Walker, Anthony C. LegonAbstract:A two force-constant model is proposed for complexes of the type B⋯MX, in which B is a simple Lewis base of at least C2v symmetry and MX is any Diatomic Molecule lying along a Cn axis (n ≥ 2) of B. The model assumes a rigid subunit B and that force constants beyond quadratic are negligible. It leads to expressions that allow, in principle, the determination of three quadratic force constants F11, F12, and F22 associated with the r(B⋯M) = r2 and r(M-X) = r1 internal coordinates from the equilibrium centrifugal distortion constants DJ (e) or ΔJ (e), the equilibrium principal axis coordinates a1 and a2, and equilibrium principal moments of inertia. The model can be applied generally to complexes containing different types of intermolecular bond. For example, the intermolecular bond of B⋯MX can be a hydrogen bond if MX is a hydrogen halide, a halogen-bond if MX is a dihalogen Molecule, or a stronger, coinage-metal bond if MX is a coinage metal halide. The equations were tested for BrCN, for which accurate equilibrium spectroscopic constants and a complete force field are available. In practice, equilibrium values of DJ (e) or ΔJ (e) for B⋯MX are not available and zero-point quantities must be used instead. The effect of doing so has been tested for BrCN. The zero-point centrifugal distortion constants DJ (0) or ΔJ (0) for all B⋯MX investigated so far are of insufficient accuracy to allow F11 and F22 to be determined simultaneously, even under the assumption F12 = 0 which is shown to be reasonable for BrCN. The calculation of F22 at a series of fixed values of F11 reveals, however, that in cases for which F11 is sufficiently larger than F22, a good approximation to F22 is obtained. Plots of F22 versus F11 have been provided for Kr⋯CuCl, Xe⋯CuCl, OC⋯CuCl, and C2H2⋯AgCl as examples. Even in cases where F22 ∼ F11 (e.g., OC⋯CuCl), such plots will yield either F22 or F11 if the other becomes available.
David Demille - One of the best experts on this subject based on the ideXlab platform.
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improved magneto optical trapping of a Diatomic Molecule
New Journal of Physics, 2015Co-Authors: D J Mccarron, Eric B Norrgard, Matthew Steinecker, David DemilleAbstract:We present experimental results from a new scheme for magneto–optically trapping strontium monofluoride (SrF) Molecules, which provides increased confinement compared to our original work. The improved trap employs a new approach to magneto–optical trapping presented by Tarbutt (2015 New J. Phys. 17 015007), which provided insight for the first time into the source of the restoring force in magneto–optical traps (MOTs) where the cycling transition includes dark Zeeman sublevels (known as type-II MOTs). We measure a radial spring constant greater than in our original work with SrF, comparable to the spring constants reported in atomic type-II MOTs. We achieve a trap lifetime ms, over longer than originally reported for SrF. Finally, we demonstrate further cooling of the trapped Molecules by briefly increasing the trapping lasers' detunings. Our trapping scheme remains a straightforward extension of atomic techniques and marks a step towards the direct production of large, dense, ultracold molecular gases via laser cooling.
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improved magneto optical trapping of a Diatomic Molecule
arXiv: Atomic Physics, 2014Co-Authors: D J Mccarron, Eric B Norrgard, Matthew Steinecker, David DemilleAbstract:We present experimental results from a new scheme for magneto-optically trapping strontium monofluoride (SrF) Molecules, which provides increased confinement compared to our original work. The improved trap employs a new approach to magneto-optical trapping presented by M. Tarbutt, \emph{arXiv preprint} 1409.0244, which provided insight for the first time into the source of the restoring force in magneto-optical traps (MOTs) where the cycling transition includes dark Zeeman sublevels (known as type-II MOTs). We measure a radial spring constant $20\times$ greater than in our original work with SrF, comparable to the spring constants reported in atomic type-II MOTs. We achieve a trap lifetime $\tau_{\rm{MOT}}=136(2)$~ms, over $2\times$ longer than originally reported for SrF. Finally, we demonstrate further cooling of the trapped Molecules by briefly increasing the trapping lasers' detunings. Our trapping scheme remains a straightforward extension of atomic techniques and marks a step towards the direct production of large, dense, ultracold molecular gases via laser cooling.
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magneto optical trapping of a Diatomic Molecule
Nature, 2014Co-Authors: D J Mccarron, John Barry, Eric B Norrgard, Matthew Steinecker, David DemilleAbstract:Laser cooling and trapping are central to modern atomic physics. The most used technique in cold-atom physics is the magneto-optical trap (MOT), which combines laser cooling with a restoring force from radiation pressure. For a variety of atomic species, MOTs can capture and cool large numbers of particles to ultracold temperatures (less than ∼1 millikelvin); this has enabled advances in areas that range from optical clocks to the study of ultracold collisions, while also serving as the ubiquitous starting point for further cooling into the regime of quantum degeneracy. Magneto-optical trapping of Molecules could provide a similarly powerful starting point for the study and manipulation of ultracold molecular gases. The additional degrees of freedom associated with the vibration and rotation of Molecules, particularly their permanent electric dipole moments, allow a broad array of applications not possible with ultracold atoms. Spurred by these ideas, a variety of methods has been developed to create ultracold Molecules. Temperatures below 1 microkelvin have been demonstrated for Diatomic Molecules assembled from pre-cooled alkali atoms, but for the wider range of species amenable to direct cooling and trapping, only recently have temperatures below 100 millikelvin been achieved. The complex internal structure of Molecules complicates magneto-optical trapping. However, ideas and methods necessary for creating a molecular MOT have been developed recently. Here we demonstrate three-dimensional magneto-optical trapping of a Diatomic Molecule, strontium monofluoride (SrF), at a temperature of approximately 2.5 millikelvin, the lowest yet achieved by direct cooling of a Molecule. This method is a straightforward extension of atomic techniques and is expected to be viable for a significant number of Diatomic species. With further development, we anticipate that this technique may be employed in any number of existing and proposed molecular experiments, in applications ranging from precision measurement to quantum simulation and quantum information to ultracold chemistry.
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laser cooling of a Diatomic Molecule
Nature, 2010Co-Authors: E. S. Shuman, John Barry, David DemilleAbstract:The development of Doppler laser cooling techniques allowed unprecedented access to ultracold temperatures of less 1 millikelvin. The motion of particles effectively ceases at such temperatures, enabling physical phenomena to be studied and controlled in extraordinary detail. Although laser cooling of atoms was demonstrated about 30 years ago, these techniques had not previously been extended to Molecules. Ultracold Molecules may prove even more interesting than ultracold atoms, because their greater internal complexity can potentially be exploited to investigate and manipulate a wide variety of physical phenomena, ranging from quantum information processing to chemical reactions and particle physics. Currently the only technique for producing ultracold Molecules is by binding together ultracold alkali atoms to produce bi-alkali Molecules. A team from Yale University now presents an experimental demonstration of laser cooling of a Diatomic Molecule — the polar Molecule strontium monofluoride (SrF). With further refinement, the technique should enable the production of large samples of Molecules at ultracold temperatures for species that are chemically distinct from bi-alkalis. Laser cooling has not yet been extended to Molecules because of their complex internal structure. At present, the only technique for producing ultracold Molecules is to bind ultracold alkali atoms to produce bialkali Molecules. These authors experimentally demonstrate laser cooling of the polar Molecule strontium monofluoride, reaching temperatures of a few millikelvin or less. The technique should allow the production of Molecules at microkelvin temperatures for species that are chemically distinct from bialkalis. It has been roughly three decades since laser cooling techniques produced ultracold atoms1,2,3, leading to rapid advances in a wide array of fields. Laser cooling has not yet been extended to Molecules because of their complex internal structure. However, this complexity makes Molecules potentially useful for a wide range of applications4. For example, heteronuclear Molecules possess permanent electric dipole moments that lead to long-range, tunable, anisotropic dipole–dipole interactions. The combination of the dipole–dipole interaction and the precise control over molecular degrees of freedom possible at ultracold temperatures makes ultracold Molecules attractive candidates for use in quantum simulations of condensed-matter systems5 and in quantum computation6. Also, ultracold Molecules could provide unique opportunities for studying chemical dynamics7,8 and for tests of fundamental symmetries9,10,11. Here we experimentally demonstrate laser cooling of the polar Molecule strontium monofluoride (SrF). Using an optical cycling scheme requiring only three lasers12, we have observed both Sisyphus and Doppler cooling forces that reduce the transverse temperature of a SrF molecular beam substantially, to a few millikelvin or less. At present, the only technique for producing ultracold Molecules is to bind together ultracold alkali atoms through Feshbach resonance13 or photoassociation14. However, proposed applications for ultracold Molecules require a variety of molecular energy-level structures (for example unpaired electronic spin5,9,11,15, Omega doublets16 and so on). Our method provides an alternative route to ultracold Molecules. In particular, it bridges the gap between ultracold (submillikelvin) temperatures and the ∼1-K temperatures attainable with directly cooled Molecules (for example with cryogenic buffer-gas cooling17 or decelerated supersonic beams18). Ultimately, our technique should allow the production of large samples of Molecules at ultracold temperatures for species that are chemically distinct from bialkalis.
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radiative force from optical cycling on a Diatomic Molecule
Physical Review Letters, 2009Co-Authors: E. S. Shuman, John Barry, David Glenn, David DemilleAbstract:We demonstrate a scheme for optical cycling in the polar, Diatomic Molecule strontium monofluoride (SrF) using the ${X}^{2}{\ensuremath{\Sigma}}^{+}\ensuremath{\rightarrow}{A}^{2}{\ensuremath{\Pi}}_{1/2}$ electronic transition. SrF's highly diagonal Franck-Condon factors suppress vibrational branching. We eliminate rotational branching by employing a quasicycling $N=1\ensuremath{\rightarrow}{N}^{\ensuremath{'}}=0$ type transition in conjunction with magnetic field remixing of dark Zeeman sublevels. We observe cycling fluorescence and deflection through radiative force of an SrF molecular beam using this scheme. With straightforward improvements our scheme promises to allow more than ${10}^{5}$ photon scatters, possibly enabling the direct laser cooling of SrF.
Dror M Bittner - One of the best experts on this subject based on the ideXlab platform.
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a two force constant model for complexes b m x b is a lewis base and mx is any Diatomic Molecule intermolecular stretching force constants from centrifugal distortion constants dj or δj
Journal of Chemical Physics, 2016Co-Authors: Dror M Bittner, Nicholas R Walker, Anthony C. LegonAbstract:A two force-constant model is proposed for complexes of the type B⋯MX, in which B is a simple Lewis base of at least C2v symmetry and MX is any Diatomic Molecule lying along a Cn axis (n ≥ 2) of B. The model assumes a rigid subunit B and that force constants beyond quadratic are negligible. It leads to expressions that allow, in principle, the determination of three quadratic force constants F11, F12, and F22 associated with the r(B⋯M) = r2 and r(M–X) = r1 internal coordinates from the equilibrium centrifugal distortion constants DJe or ΔJe, the equilibrium principal axis coordinates a1 and a2, and equilibrium principal moments of inertia. The model can be applied generally to complexes containing different types of intermolecular bond. For example, the intermolecular bond of B⋯MX can be a hydrogen bond if MX is a hydrogen halide, a halogen-bond if MX is a dihalogen Molecule, or a stronger, coinage-metal bond if MX is a coinage metal halide. The equations were tested for BrCN, for which accurate equilibri...
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a two force constant model for complexes b m x b is a lewis base and mx is any Diatomic Molecule intermolecular stretching force constants from centrifugal distortion constants dj or δj
Journal of Chemical Physics, 2016Co-Authors: Dror M Bittner, Nicholas R Walker, Anthony C. LegonAbstract:A two force-constant model is proposed for complexes of the type B⋯MX, in which B is a simple Lewis base of at least C2v symmetry and MX is any Diatomic Molecule lying along a Cn axis (n ≥ 2) of B. The model assumes a rigid subunit B and that force constants beyond quadratic are negligible. It leads to expressions that allow, in principle, the determination of three quadratic force constants F11, F12, and F22 associated with the r(B⋯M) = r2 and r(M-X) = r1 internal coordinates from the equilibrium centrifugal distortion constants DJ (e) or ΔJ (e), the equilibrium principal axis coordinates a1 and a2, and equilibrium principal moments of inertia. The model can be applied generally to complexes containing different types of intermolecular bond. For example, the intermolecular bond of B⋯MX can be a hydrogen bond if MX is a hydrogen halide, a halogen-bond if MX is a dihalogen Molecule, or a stronger, coinage-metal bond if MX is a coinage metal halide. The equations were tested for BrCN, for which accurate equilibrium spectroscopic constants and a complete force field are available. In practice, equilibrium values of DJ (e) or ΔJ (e) for B⋯MX are not available and zero-point quantities must be used instead. The effect of doing so has been tested for BrCN. The zero-point centrifugal distortion constants DJ (0) or ΔJ (0) for all B⋯MX investigated so far are of insufficient accuracy to allow F11 and F22 to be determined simultaneously, even under the assumption F12 = 0 which is shown to be reasonable for BrCN. The calculation of F22 at a series of fixed values of F11 reveals, however, that in cases for which F11 is sufficiently larger than F22, a good approximation to F22 is obtained. Plots of F22 versus F11 have been provided for Kr⋯CuCl, Xe⋯CuCl, OC⋯CuCl, and C2H2⋯AgCl as examples. Even in cases where F22 ∼ F11 (e.g., OC⋯CuCl), such plots will yield either F22 or F11 if the other becomes available.
J G Eden - One of the best experts on this subject based on the ideXlab platform.
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spin polarization of rb and cs np 2 p_ 3 2 n 5 6 atoms by circularly polarized photoexcitation of a transient Diatomic Molecule
Physical Review Letters, 2017Co-Authors: Andrey E Mironov, J D Hewitt, J G EdenAbstract:We report the selective population of Rb or Cs np ^{2}P_{3/2} (n=5, 6; F=4, 5) hyperfine states by the photodissociation of a transient, alkali-rare gas Diatomic Molecule. Circularly polarized (σ^{-}), amplified spontaneous emission (ASE) on the D_{2} line of Rb or Cs (780.0 and 852.1 nm, respectively) is generated when Rb-Xe or Cs-Xe ground state collision pairs are photoexcited by a σ^{+}-polarized optical field having a wavelength within the D_{2} blue satellite continuum, associated with the B^{2}Σ_{1/2}^{+}←X^{2}Σ_{1/2}^{+} (free←free) transition of the Diatomic Molecule. The degree of spin polarization of Cs (6p ^{2}P_{3/2}), specifically, is found to be dependent on the interatomic distance (R) at which the excited complex is born, a result attributed to the structure of the B^{2}Σ_{1/2}^{+} state. For Cs-Xe atomic pairs, tuning the wavelength of the optical field from 843 to 848 nm varies the degree of circular polarization of the ASE from 63% to almost unity because of the perturbation, in the 5≤R≤6 A interval, of the ^{2}Σ_{1/2}^{+} potential by a dσ molecular orbital associated with a higher ^{2}Λ electronic state. Monitoring only the Cs 6p ^{2}P_{3/2} spin polarization reveals a previously unobserved interaction of CsXe (B^{2}Σ_{1/2}^{+}) with the lowest vibrational levels of a ^{2}Λ state derived from Cs (5d)+Xe. By inserting a molecular intermediate into the alkali atom excitation mechanism, these experiments realize electronic spin polarization through populating no more than two np ^{2}P_{3/2} hyperfine states, and demonstrate a sensitive spectroscopic probe of R-dependent state-state interactions and their impact on interatomic potentials.
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spin polarization of rb and cs n p p 2 3 2 n 5 6 atoms by circularly polarized photoexcitation of a transient Diatomic Molecule
Physical Review Letters, 2017Co-Authors: Andrey E Mironov, J D Hewitt, J G EdenAbstract:We report the selective population of Rb or Cs $np$ ${^{2}P}_{\frac{3}{2}}$ ($n=5$, 6; $F=4$, 5) hyperfine states by the photodissociation of a transient, alkali-rare gas Diatomic Molecule. Circularly polarized (${\ensuremath{\sigma}}^{\ensuremath{-}}$), amplified spontaneous emission (ASE) on the ${D}_{2}$ line of Rb or Cs (780.0 and 852.1 nm, respectively) is generated when Rb-Xe or Cs-Xe ground state collision pairs are photoexcited by a ${\ensuremath{\sigma}}^{+}$-polarized optical field having a wavelength within the ${D}_{2}$ blue satellite continuum, associated with the $B{^{2}\mathrm{\ensuremath{\Sigma}}}_{\frac{1}{2}}^{+}\ensuremath{\leftarrow}X{^{2}\mathrm{\ensuremath{\Sigma}}}_{\frac{1}{2}}^{+}$ ($\text{free}\ensuremath{\leftarrow}\text{free}$) transition of the Diatomic Molecule. The degree of spin polarization of Cs ($6p$ $^{2}{P}_{\frac{3}{2}}$), specifically, is found to be dependent on the interatomic distance ($R$) at which the excited complex is born, a result attributed to the structure of the $B{^{2}\mathrm{\ensuremath{\Sigma}}}_{\frac{1}{2}}^{+}$ state. For Cs-Xe atomic pairs, tuning the wavelength of the optical field from 843 to 848 nm varies the degree of circular polarization of the ASE from 63% to almost unity because of the perturbation, in the $5\ensuremath{\le}R\ensuremath{\le}6\text{ }\text{ }\AA{}$ interval, of the ${^{2}\mathrm{\ensuremath{\Sigma}}}_{\frac{1}{2}}^{+}$ potential by a $d\ensuremath{\sigma}$ molecular orbital associated with a higher $^{2}\mathrm{\ensuremath{\Lambda}}$ electronic state. Monitoring only the Cs $6p$ $^{2}{P}_{\frac{3}{2}}$ spin polarization reveals a previously unobserved interaction of CsXe ($B{^{2}\mathrm{\ensuremath{\Sigma}}}_{\frac{1}{2}}^{+}$) with the lowest vibrational levels of a $^{2}\mathrm{\ensuremath{\Lambda}}$ state derived from Cs $(5d)+\mathrm{Xe}$. By inserting a molecular intermediate into the alkali atom excitation mechanism, these experiments realize electronic spin polarization through populating no more than two $np$ ${^{2}P}_{\frac{3}{2}}$ hyperfine states, and demonstrate a sensitive spectroscopic probe of $R$-dependent state-state interactions and their impact on interatomic potentials.
John Barry - One of the best experts on this subject based on the ideXlab platform.
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magneto optical trapping of a Diatomic Molecule
Nature, 2014Co-Authors: D J Mccarron, John Barry, Eric B Norrgard, Matthew Steinecker, David DemilleAbstract:Laser cooling and trapping are central to modern atomic physics. The most used technique in cold-atom physics is the magneto-optical trap (MOT), which combines laser cooling with a restoring force from radiation pressure. For a variety of atomic species, MOTs can capture and cool large numbers of particles to ultracold temperatures (less than ∼1 millikelvin); this has enabled advances in areas that range from optical clocks to the study of ultracold collisions, while also serving as the ubiquitous starting point for further cooling into the regime of quantum degeneracy. Magneto-optical trapping of Molecules could provide a similarly powerful starting point for the study and manipulation of ultracold molecular gases. The additional degrees of freedom associated with the vibration and rotation of Molecules, particularly their permanent electric dipole moments, allow a broad array of applications not possible with ultracold atoms. Spurred by these ideas, a variety of methods has been developed to create ultracold Molecules. Temperatures below 1 microkelvin have been demonstrated for Diatomic Molecules assembled from pre-cooled alkali atoms, but for the wider range of species amenable to direct cooling and trapping, only recently have temperatures below 100 millikelvin been achieved. The complex internal structure of Molecules complicates magneto-optical trapping. However, ideas and methods necessary for creating a molecular MOT have been developed recently. Here we demonstrate three-dimensional magneto-optical trapping of a Diatomic Molecule, strontium monofluoride (SrF), at a temperature of approximately 2.5 millikelvin, the lowest yet achieved by direct cooling of a Molecule. This method is a straightforward extension of atomic techniques and is expected to be viable for a significant number of Diatomic species. With further development, we anticipate that this technique may be employed in any number of existing and proposed molecular experiments, in applications ranging from precision measurement to quantum simulation and quantum information to ultracold chemistry.
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Laser Cooling and Slowing of a Diatomic Molecule
2013Co-Authors: John BarryAbstract:Abstract : Laser cooling and trapping are central to modern atomic physics. It has been roughly three decades since laser cooling techniques produced ultracold atoms, leading to rapid advances in a vast array of fields and a number of Nobel prizes. Prior to the work presented in this thesis, laser cooling had not yet been extended to Molecules because of their complex internal structure. However, this complexity makes Molecules potentially useful for a wide range of applications. The first direct laser cooling of a Molecule and further results we present here provide a new route to ultracold temperatures for Molecules. In particular, these methods bridge the gap between ultracold temperatures and the approximately 1 kelvin temperatures attainable with directly cooled Molecules (e.g. with cryogenic buffer gas cooling or decelerated supersonic beams). Using the carefully chosen Molecule strontium monofluoride (SrF), decays to unwanted vibrational states are suppressed. Driving a transition with rotational quantum number R=1 to an excited state with R0=0 eliminates decays to unwanted rotational states. The dark ground-state Zeeman sublevels present in this specific scheme are remixed via a static magnetic field. Using three lasers for this scheme, a given Molecule should undergo an average of approximately 100, 000 photon absorption/emission cycles before being lost via unwanted decays. This number of cycles should be sufficient to load a magneto-optical trap (MOT) of Molecules. In this thesis, we demonstrate transverse cooling of an SrF beam, in both Doppler and a Sisyphus-type cooling regimes. We also realize longitudinal slowing of an SrF beam. Finally, we detail current progress towards trapping SrF in a MOT. Ultimately, this technique should enable the production of large samples of Molecules at ultracold temperatures for Molecules chemically distinct from competing methods.
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laser cooling of a Diatomic Molecule
Nature, 2010Co-Authors: E. S. Shuman, John Barry, David DemilleAbstract:The development of Doppler laser cooling techniques allowed unprecedented access to ultracold temperatures of less 1 millikelvin. The motion of particles effectively ceases at such temperatures, enabling physical phenomena to be studied and controlled in extraordinary detail. Although laser cooling of atoms was demonstrated about 30 years ago, these techniques had not previously been extended to Molecules. Ultracold Molecules may prove even more interesting than ultracold atoms, because their greater internal complexity can potentially be exploited to investigate and manipulate a wide variety of physical phenomena, ranging from quantum information processing to chemical reactions and particle physics. Currently the only technique for producing ultracold Molecules is by binding together ultracold alkali atoms to produce bi-alkali Molecules. A team from Yale University now presents an experimental demonstration of laser cooling of a Diatomic Molecule — the polar Molecule strontium monofluoride (SrF). With further refinement, the technique should enable the production of large samples of Molecules at ultracold temperatures for species that are chemically distinct from bi-alkalis. Laser cooling has not yet been extended to Molecules because of their complex internal structure. At present, the only technique for producing ultracold Molecules is to bind ultracold alkali atoms to produce bialkali Molecules. These authors experimentally demonstrate laser cooling of the polar Molecule strontium monofluoride, reaching temperatures of a few millikelvin or less. The technique should allow the production of Molecules at microkelvin temperatures for species that are chemically distinct from bialkalis. It has been roughly three decades since laser cooling techniques produced ultracold atoms1,2,3, leading to rapid advances in a wide array of fields. Laser cooling has not yet been extended to Molecules because of their complex internal structure. However, this complexity makes Molecules potentially useful for a wide range of applications4. For example, heteronuclear Molecules possess permanent electric dipole moments that lead to long-range, tunable, anisotropic dipole–dipole interactions. The combination of the dipole–dipole interaction and the precise control over molecular degrees of freedom possible at ultracold temperatures makes ultracold Molecules attractive candidates for use in quantum simulations of condensed-matter systems5 and in quantum computation6. Also, ultracold Molecules could provide unique opportunities for studying chemical dynamics7,8 and for tests of fundamental symmetries9,10,11. Here we experimentally demonstrate laser cooling of the polar Molecule strontium monofluoride (SrF). Using an optical cycling scheme requiring only three lasers12, we have observed both Sisyphus and Doppler cooling forces that reduce the transverse temperature of a SrF molecular beam substantially, to a few millikelvin or less. At present, the only technique for producing ultracold Molecules is to bind together ultracold alkali atoms through Feshbach resonance13 or photoassociation14. However, proposed applications for ultracold Molecules require a variety of molecular energy-level structures (for example unpaired electronic spin5,9,11,15, Omega doublets16 and so on). Our method provides an alternative route to ultracold Molecules. In particular, it bridges the gap between ultracold (submillikelvin) temperatures and the ∼1-K temperatures attainable with directly cooled Molecules (for example with cryogenic buffer-gas cooling17 or decelerated supersonic beams18). Ultimately, our technique should allow the production of large samples of Molecules at ultracold temperatures for species that are chemically distinct from bialkalis.
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radiative force from optical cycling on a Diatomic Molecule
Physical Review Letters, 2009Co-Authors: E. S. Shuman, John Barry, David Glenn, David DemilleAbstract:We demonstrate a scheme for optical cycling in the polar, Diatomic Molecule strontium monofluoride (SrF) using the ${X}^{2}{\ensuremath{\Sigma}}^{+}\ensuremath{\rightarrow}{A}^{2}{\ensuremath{\Pi}}_{1/2}$ electronic transition. SrF's highly diagonal Franck-Condon factors suppress vibrational branching. We eliminate rotational branching by employing a quasicycling $N=1\ensuremath{\rightarrow}{N}^{\ensuremath{'}}=0$ type transition in conjunction with magnetic field remixing of dark Zeeman sublevels. We observe cycling fluorescence and deflection through radiative force of an SrF molecular beam using this scheme. With straightforward improvements our scheme promises to allow more than ${10}^{5}$ photon scatters, possibly enabling the direct laser cooling of SrF.