1
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Vilas NB, Robichaud P, Hallas C, Li GK, Anderegg L, Doyle JM. An optical tweezer array of ultracold polyatomic molecules. Nature 2024; 628:282-286. [PMID: 38570690 DOI: 10.1038/s41586-024-07199-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 02/13/2024] [Indexed: 04/05/2024]
Abstract
Polyatomic molecules have rich structural features that make them uniquely suited to applications in quantum information science1-3, quantum simulation4-6, ultracold chemistry7 and searches for physics beyond the standard model8-10. However, a key challenge is fully controlling both the internal quantum state and the motional degrees of freedom of the molecules. Here we demonstrate the creation of an optical tweezer array of individual polyatomic molecules, CaOH, with quantum control of their internal quantum state. The complex quantum structure of CaOH results in a non-trivial dependence of the molecules' behaviour on the tweezer light wavelength. We control this interaction and directly and non-destructively image individual molecules in the tweezer array with a fidelity greater than 90%. The molecules are manipulated at the single internal quantum state level, thus demonstrating coherent state control in a tweezer array. The platform demonstrated here will enable a variety of experiments using individual polyatomic molecules with arbitrary spatial arrangement.
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Affiliation(s)
- Nathaniel B Vilas
- Department of Physics, Harvard University, Cambridge, MA, USA.
- Harvard-MIT Center for Ultracold Atoms, Cambridge, MA, USA.
| | - Paige Robichaud
- Department of Physics, Harvard University, Cambridge, MA, USA
- Harvard-MIT Center for Ultracold Atoms, Cambridge, MA, USA
| | - Christian Hallas
- Department of Physics, Harvard University, Cambridge, MA, USA
- Harvard-MIT Center for Ultracold Atoms, Cambridge, MA, USA
| | - Grace K Li
- Department of Physics, Harvard University, Cambridge, MA, USA
- Harvard-MIT Center for Ultracold Atoms, Cambridge, MA, USA
| | - Loïc Anderegg
- Department of Physics, Harvard University, Cambridge, MA, USA
- Harvard-MIT Center for Ultracold Atoms, Cambridge, MA, USA
| | - John M Doyle
- Department of Physics, Harvard University, Cambridge, MA, USA
- Harvard-MIT Center for Ultracold Atoms, Cambridge, MA, USA
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2
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Zhang C, Hutzler NR, Cheng L. Intensity-Borrowing Mechanisms Pertinent to Laser Cooling of Linear Polyatomic Molecules. J Chem Theory Comput 2023. [PMID: 37384588 DOI: 10.1021/acs.jctc.3c00408] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/01/2023]
Abstract
A study of the intensity-borrowing mechanisms important to optical cycling transitions in laser-coolable polyatomic molecules arising from non-adiabatic coupling, contributions beyond the Franck-Condon approximation, and Fermi resonances is reported. It has been shown to be necessary to include non-adiabatic coupling to obtain computational accuracy that is sufficient to be useful for laser cooling of molecules. The predicted vibronic branching ratios using perturbation theory based on the non-adiabatic mechanisms have been demonstrated to agree well with those obtained from variational discrete variable representation calculations for representative molecules including CaOH, SrOH, and YbOH. The electron-correlation and basis-set effects on the calculated transition properties, including the vibronic coupling constants, the spin-orbit coupling matrix elements, and the transition dipole moments, and on the calculated branching ratios have been thoroughly studied. The vibronic branching ratios predicted using the present methodologies demonstrate that RaOH is a promising radioactive molecule candidate for laser cooling.
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Affiliation(s)
- Chaoqun Zhang
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Nicholas R Hutzler
- Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, California 91125, United States
| | - Lan Cheng
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
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3
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Zhelyazkova V, Martins FBV, Schilling S, Merkt F. Reaction of an Ion and a Free Radical near 0 K: He + + NO → He + N + + O. J Phys Chem A 2023; 127:1458-1468. [PMID: 36752385 PMCID: PMC9940198 DOI: 10.1021/acs.jpca.2c08221] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
The reactions between ions and free radicals are among the fastest chemical reactions. They are predicted to proceed with large rates, even near 0 K, but so far, this prediction has not been verified experimentally. We report on measurements of the rate coefficient of the reaction between the ion He+ and the free radical NO at collision energies in the range between 0 and ∼ kB·10 K. To avoid heating of the ions by stray electric fields, the reaction is observed within the large orbit of a Rydberg electron of principal quantum number n ≥ 30, which shields the ion from external electric fields without affecting the reaction. Low collision energies are reached by merging a supersonic beam of He Rydberg atoms with a supersonic beam of NO molecules and adjusting their relative velocity using a chip-based Rydberg-Stark decelerator and deflector. We observe a strong enhancement of the reaction rate at collision energies below ∼kB·2 K. This enhancement is interpreted on the basis of adiabatic-channel capture-rate calculations as arising from the near-degenerate rotational levels of opposite parity resulting from the Λ-doubling in the X 2Π1/2 ground state of NO. With these new results, we examine the reliability of broadly used approximate analytic expressions for the thermal rate constants of ion-molecule reactions at low temperatures.
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4
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Vilas NB, Hallas C, Anderegg L, Robichaud P, Winnicki A, Mitra D, Doyle JM. Magneto-optical trapping and sub-Doppler cooling of a polyatomic molecule. Nature 2022; 606:70-74. [PMID: 35650357 DOI: 10.1038/s41586-022-04620-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 03/04/2022] [Indexed: 11/09/2022]
Abstract
Laser cooling and trapping1,2, and magneto-optical trapping methods in particular2, have enabled groundbreaking advances in science, including Bose-Einstein condensation3-5, quantum computation with neutral atoms6,7 and high-precision optical clocks8. Recently, magneto-optical traps (MOTs) of diatomic molecules have been demonstrated9-12, providing access to research in quantum simulation13 and searches for physics beyond the standard model14. Compared with diatomic molecules, polyatomic molecules have distinct rotational and vibrational degrees of freedom that promise a variety of transformational possibilities. For example, ultracold polyatomic molecules would be uniquely suited to applications in quantum computation and simulation15-17, ultracold collisions18, quantum chemistry19 and beyond-the-standard-model searches20,21. However, the complexity of these molecules has so far precluded the realization of MOTs for polyatomic species. Here we demonstrate magneto-optical trapping of a polyatomic molecule, calcium monohydroxide (CaOH). After trapping, the molecules are laser cooled in a blue-detuned optical molasses to a temperature of 110 μK, which is below the Doppler cooling limit. The temperatures and densities achieved here make CaOH a viable candidate for a wide variety of quantum science applications, including quantum simulation and computation using optical tweezer arrays15,17,22,23. This work also suggests that laser cooling and magneto-optical trapping of many other polyatomic species24-27 will be both feasible and practical.
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Affiliation(s)
- Nathaniel B Vilas
- Department of Physics, Harvard University, Cambridge, MA, USA. .,Harvard-MIT Center for Ultracold Atoms, Cambridge, MA, USA.
| | - Christian Hallas
- Department of Physics, Harvard University, Cambridge, MA, USA.,Harvard-MIT Center for Ultracold Atoms, Cambridge, MA, USA
| | - Loïc Anderegg
- Department of Physics, Harvard University, Cambridge, MA, USA.,Harvard-MIT Center for Ultracold Atoms, Cambridge, MA, USA
| | - Paige Robichaud
- Department of Physics, Harvard University, Cambridge, MA, USA.,Harvard-MIT Center for Ultracold Atoms, Cambridge, MA, USA
| | - Andrew Winnicki
- Department of Physics, Harvard University, Cambridge, MA, USA.,Harvard-MIT Center for Ultracold Atoms, Cambridge, MA, USA
| | - Debayan Mitra
- Department of Physics, Harvard University, Cambridge, MA, USA.,Harvard-MIT Center for Ultracold Atoms, Cambridge, MA, USA.,Department of Physics, Columbia University, New York, NY, USA
| | - John M Doyle
- Department of Physics, Harvard University, Cambridge, MA, USA.,Harvard-MIT Center for Ultracold Atoms, Cambridge, MA, USA
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5
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Wu LY, Miossec C, Heazlewood BR. Low-temperature reaction dynamics of paramagnetic species in the gas phase. Chem Commun (Camb) 2022; 58:3240-3254. [PMID: 35188499 PMCID: PMC8902758 DOI: 10.1039/d1cc06394d] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 01/12/2022] [Indexed: 12/12/2022]
Abstract
Radicals are abundant in a range of important gas-phase environments. They are prevalent in the atmosphere, in interstellar space, and in combustion processes. As such, understanding how radicals react is essential for the development of accurate models of the complex chemistry occurring in these gas-phase environments. By controlling the properties of the colliding reactants, we can also gain insights into how radical reactions occur on a fundamental level. Recent years have seen remarkable advances in the breadth of experimental methods successfully applied to the study of reaction dynamics involving paramagnetic species-from improvements to the well-known crossed molecular beams approach to newer techniques involving magnetically guided and decelerated beams. Coupled with ever-improving theoretical methods, quantum features are being observed and interesting insights into reaction dynamics are being uncovered in an increasingly diverse range of systems. In this highlight article, we explore some of the exciting recent developments in the study of chemical dynamics involving paramagnetic species. We focus on low-energy reactive collisions involving neutral radical species, where the reaction parameters are controlled. We conclude by identifying some of the limitations of current methods and exploring possible new directions for the field.
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Affiliation(s)
- Lok Yiu Wu
- The Oliver Lodge, Department of Physics, University of Liverpool, Oxford Street, Liverpool, L69 7ZE, UK.
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
| | - Chloé Miossec
- The Oliver Lodge, Department of Physics, University of Liverpool, Oxford Street, Liverpool, L69 7ZE, UK.
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
| | - Brianna R Heazlewood
- The Oliver Lodge, Department of Physics, University of Liverpool, Oxford Street, Liverpool, L69 7ZE, UK.
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6
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Miossec C, Hejduk M, Pandey R, Coughlan NJA, Heazlewood BR. Design and characterization of a cryogenic linear Paul ion trap for ion-neutral reaction studies. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:033201. [PMID: 35364974 DOI: 10.1063/5.0080458] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 02/16/2022] [Indexed: 06/14/2023]
Abstract
Ultra-high vacuum conditions are ideal for the study of trapped ions. They offer an almost perturbation-free environment, where ions confined in traps can be studied for extended periods of time-facilitating precision measurements and allowing infrequent events to be observed. However, if one wishes to study processes involving molecular ions, it is important to consider the effect of blackbody radiation (BBR). The vast majority of molecular ions interact with BBR. At 300 K, state selection in trapped molecular ions can be rapidly lost (in a matter of seconds). To address this issue, and to maintain state selectivity in trapped molecular ions, a cryogenic ion trap chamber has been constructed and characterized. At the center of the apparatus is a linear Paul ion trap, where Coulomb crystals can be formed for ion-neutral reaction studies. Optical access is provided, for lasers and for imaging of the crystals, alongside ion optics and a flight tube for recording time-of-flight mass spectra. The ion trap region, encased within two nested temperature stages, reaches temperatures below 9 K. To avoid vibrations from the cryocooler impeding laser cooling or imaging of the ions, vibration-damping elements are explicitly included. These components successfully inhibit the coupling of vibrations from the cold head to the ion trap-confirmed by accelerometer measurements and by the resolution of images recorded at the trap center (at 9 and 295 K). These results confirm that the cryogenic ion trap apparatus meets all requirements for studying ion-neutral reactions under cold, controlled conditions.
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Affiliation(s)
- Chloé Miossec
- Department of Physics, University of Liverpool, Oxford Street, Liverpool L69 7ZE, United Kingdom
| | - Michal Hejduk
- Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Rahul Pandey
- Department of Physics, University of Liverpool, Oxford Street, Liverpool L69 7ZE, United Kingdom
| | - Neville J A Coughlan
- Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Brianna R Heazlewood
- Department of Physics, University of Liverpool, Oxford Street, Liverpool L69 7ZE, United Kingdom
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7
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Augenbraun BL, Frenett A, Sawaoka H, Hallas C, Vilas NB, Nasir A, Lasner ZD, Doyle JM. Zeeman-Sisyphus Deceleration of Molecular Beams. PHYSICAL REVIEW LETTERS 2021; 127:263002. [PMID: 35029484 DOI: 10.1103/physrevlett.127.263002] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 11/01/2021] [Indexed: 06/14/2023]
Abstract
We present a robust, continuous molecular decelerator that employs high magnetic fields and few optical pumping steps. CaOH molecules are slowed, accumulating at low velocities in a range sufficient for loading both magnetic and magneto-optical traps. During the slowing, the molecules scatter only seven photons, removing around 8 K of energy. Because large energies can be removed with only a few spontaneous radiative decays, this method can in principle be applied to nearly any paramagnetic atomic or molecular species, opening a general path to trapping of complex molecules.
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Affiliation(s)
- Benjamin L Augenbraun
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA and Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
| | - Alexander Frenett
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA and Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
| | - Hiromitsu Sawaoka
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA and Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
| | - Christian Hallas
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA and Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
| | - Nathaniel B Vilas
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA and Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
| | - Abdullah Nasir
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA and Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
| | - Zack D Lasner
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA and Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
| | - John M Doyle
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA and Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
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8
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Mohamed O, Wu LY, Tsikritea A, Heazlewood BR. Optimizing the intensity and purity of a Zeeman-decelerated beam. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:093201. [PMID: 34598488 DOI: 10.1063/5.0061379] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 08/31/2021] [Indexed: 06/13/2023]
Abstract
A pure, state-selected beam of gas-phase radicals is an important tool for the precise study of radical reactions that are astrochemically and atmospherically relevant. Generating such a beam has proven to be an ongoing challenge for the scientific community. Using evolutionary algorithms to optimize the variable experimental parameters, the passage of state- and velocity-selected hydrogen atoms can be optimized as they travel through a 12-stage Zeeman decelerator and a magnetic guide. Only H atoms traveling at the target velocity are present in the beam that reaches the detection region, from a source containing a mixture of different species. All other species-including seed gases, precursor molecules, other dissociation products, and H atoms traveling outside the target velocity-are removed from the beam. The fully optimized parameters yield a pure H-atom beam containing twice as many target particles and a narrower velocity distribution compared to beams produced when only the Zeeman decelerator is optimized. These significant improvements highlight the importance of considering the passage of all target particles in the beam as they pass through all elements of the experimental apparatus.
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Affiliation(s)
- Omar Mohamed
- Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Lok Yiu Wu
- Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Andriana Tsikritea
- Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Brianna R Heazlewood
- Department of Physics, University of Liverpool, Oxford Street, Liverpool L69 7ZE, United Kingdom
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9
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Heazlewood BR. Quantum-State Control and Manipulation of Paramagnetic Molecules with Magnetic Fields. Annu Rev Phys Chem 2021; 72:353-373. [PMID: 33492979 DOI: 10.1146/annurev-physchem-090419-053842] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Since external magnetic fields were first employed to deflect paramagnetic atoms in 1921, a range of magnetic field-based methods have been introduced to state-selectively manipulate paramagnetic species. These methods include magnetic guides, which selectively filter paramagnetic species from all other components of a beam, and magnetic traps, where paramagnetic species can be spatially confined for extended periods of time. However, many of these techniques were developed for atomic-rather than molecular-paramagnetic species. It has proven challenging to apply some of these experimental methods developed for atoms to paramagnetic molecules. Thanks to the emergence of new experimental approaches and new combinations of existing techniques, the past decade has seen significant progress toward the manipulation and control of paramagnetic molecules. This review identifies the key methods that have been implemented for the state-selective manipulation of paramagnetic molecules-discussing the motivation, state of the art, and future prospects of the field. Key applications include the ability to control chemical interactions, undertake precise spectroscopic measurements, and challenge our understanding of chemical reactivity at a fundamental level.
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10
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Abstract
The prospect of cooling matter down to temperatures that are close to absolute zero raises intriguing questions about how chemical reactivity changes under these extreme conditions. Although some types of chemical reaction still occur at 1 μK, they can no longer adhere to the conventional picture of reactants passing over an activation energy barrier to become products. Indeed, at ultracold temperatures, the system enters a fully quantum regime, and quantum mechanics replaces the classical picture of colliding particles. In this Review, we discuss recent experimental and theoretical developments that allow us to explore chemical reactions at temperatures that range from 100 K to 500 nK. Although the field is still in its infancy, exceptional control has already been demonstrated over reactivity at low temperatures.
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11
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Jansen P, Merkt F. Manipulating beams of paramagnetic atoms and molecules using inhomogeneous magnetic fields. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2020; 120-121:118-148. [PMID: 33198967 DOI: 10.1016/j.pnmrs.2020.08.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 08/07/2020] [Accepted: 08/10/2020] [Indexed: 06/11/2023]
Abstract
We review methods to manipulate the motion of pulsed supersonic atomic and molecular beams using time-independent and -dependent inhomogeneous magnetic fields. In addition, we discuss current and possible future applications and research directions.
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Affiliation(s)
- Paul Jansen
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
| | - Frédéric Merkt
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
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12
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Mitra D, Vilas NB, Hallas C, Anderegg L, Augenbraun BL, Baum L, Miller C, Raval S, Doyle JM. Direct laser cooling of a symmetric top molecule. Science 2020; 369:1366-1369. [DOI: 10.1126/science.abc5357] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Accepted: 07/10/2020] [Indexed: 11/02/2022]
Abstract
Ultracold polyatomic molecules have potentially wide-ranging applications in quantum simulation and computation, particle physics, and quantum chemistry. For atoms and small molecules, direct laser cooling has proven to be a powerful tool for quantum science in the ultracold regime. However, the feasibility of laser-cooling larger, nonlinear polyatomic molecules has remained unknown because of their complex structure. We laser-cooled the symmetric top molecule calcium monomethoxide (CaOCH3), reducing the temperature of ~104 molecules from 22 ± 1 millikelvin to 1.8 ± 0.7 millikelvin in one dimension and state-selectively cooling two nuclear spin isomers. These results demonstrate that the use of proper ro-vibronic transitions enables laser cooling of nonlinear molecules, thereby opening a path to efficient cooling of chiral molecules and, eventually, optical tweezer arrays of complex polyatomic species.
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Affiliation(s)
- Debayan Mitra
- Department of Physics, Harvard University, Cambridge, MA 02138, USA, and Harvard-MIT Center for Ultracold Atoms, Cambridge, MA 02138, USA
| | - Nathaniel B. Vilas
- Department of Physics, Harvard University, Cambridge, MA 02138, USA, and Harvard-MIT Center for Ultracold Atoms, Cambridge, MA 02138, USA
| | - Christian Hallas
- Department of Physics, Harvard University, Cambridge, MA 02138, USA, and Harvard-MIT Center for Ultracold Atoms, Cambridge, MA 02138, USA
| | - Loïc Anderegg
- Department of Physics, Harvard University, Cambridge, MA 02138, USA, and Harvard-MIT Center for Ultracold Atoms, Cambridge, MA 02138, USA
| | - Benjamin L. Augenbraun
- Department of Physics, Harvard University, Cambridge, MA 02138, USA, and Harvard-MIT Center for Ultracold Atoms, Cambridge, MA 02138, USA
| | - Louis Baum
- Department of Physics, Harvard University, Cambridge, MA 02138, USA, and Harvard-MIT Center for Ultracold Atoms, Cambridge, MA 02138, USA
| | - Calder Miller
- Department of Physics, Harvard University, Cambridge, MA 02138, USA, and Harvard-MIT Center for Ultracold Atoms, Cambridge, MA 02138, USA
| | - Shivam Raval
- Department of Physics, Harvard University, Cambridge, MA 02138, USA, and Harvard-MIT Center for Ultracold Atoms, Cambridge, MA 02138, USA
| | - John M. Doyle
- Department of Physics, Harvard University, Cambridge, MA 02138, USA, and Harvard-MIT Center for Ultracold Atoms, Cambridge, MA 02138, USA
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13
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Baum L, Vilas NB, Hallas C, Augenbraun BL, Raval S, Mitra D, Doyle JM. 1D Magneto-Optical Trap of Polyatomic Molecules. PHYSICAL REVIEW LETTERS 2020; 124:133201. [PMID: 32302203 DOI: 10.1103/physrevlett.124.133201] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 03/09/2020] [Indexed: 06/11/2023]
Abstract
We demonstrate a 1D magneto-optical trap of the polar free radical calcium monohydroxide (CaOH). A quasiclosed cycling transition is established to scatter ∼10^{3} photons per molecule, predominantly limited by interaction time. This enables radiative laser cooling of CaOH while compressing the molecular beam, leading to a significant increase in on axis beam brightness and reduction in temperature from 8.4 to 1.4 mK.
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Affiliation(s)
- Louis Baum
- Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Nathaniel B Vilas
- Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Christian Hallas
- Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Benjamin L Augenbraun
- Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Shivam Raval
- Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Debayan Mitra
- Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - John M Doyle
- Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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14
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Plomp V, Gao Z, Cremers T, Besemer M, van de Meerakker SYT. High-resolution imaging of molecular collisions using a Zeeman decelerator. J Chem Phys 2020; 152:091103. [PMID: 33480725 DOI: 10.1063/1.5142817] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present the first crossed beam scattering experiment using a Zeeman decelerated molecular beam. The narrow velocity spreads of Zeeman decelerated NO (X2Π3/2, j = 3/2) radicals result in high-resolution scattering images, thereby fully resolving quantum diffraction oscillations in the angular scattering distribution for inelastic NO-Ne collisions and product-pair correlations in the radial scattering distribution for inelastic NO-O2 collisions. These measurements demonstrate similar resolution and sensitivity as in experiments using Stark decelerators, opening up possibilities for controlled and low-energy scattering experiments using chemically relevant species such as H and O atoms, O2 molecules, or NH radicals.
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Affiliation(s)
- Vikram Plomp
- Institute for Molecules and Materials, Radboud University Nijmegen, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Zhi Gao
- Institute for Molecules and Materials, Radboud University Nijmegen, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Theo Cremers
- Institute for Molecules and Materials, Radboud University Nijmegen, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Matthieu Besemer
- Institute for Molecules and Materials, Radboud University Nijmegen, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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15
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Toscano J, Lewandowski HJ, Heazlewood BR. Cold and controlled chemical reaction dynamics. Phys Chem Chem Phys 2020; 22:9180-9194. [DOI: 10.1039/d0cp00931h] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
State-to-state chemical reaction dynamics, with complete control over the reaction parameters, offers unparalleled insight into fundamental reactivity.
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Affiliation(s)
- Jutta Toscano
- JILA and the Department of Physics
- University of Colorado
- Boulder
- USA
| | | | - Brianna R. Heazlewood
- Physical and Theoretical Chemistry Laboratory (PTCL)
- Department of Chemistry
- University of Oxford
- Oxford
- UK
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16
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Collisions between cold molecules in a superconducting magnetic trap. Nature 2019; 572:189-193. [DOI: 10.1038/s41586-019-1446-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Accepted: 06/12/2019] [Indexed: 11/08/2022]
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17
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Morita M, Krems RV, Tscherbul TV. Universal Probability Distributions of Scattering Observables in Ultracold Molecular Collisions. PHYSICAL REVIEW LETTERS 2019; 123:013401. [PMID: 31386401 DOI: 10.1103/physrevlett.123.013401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 05/09/2019] [Indexed: 06/10/2023]
Abstract
Currently, quantum dynamics theory cannot be used for quantitative predictions of molecular scattering observables at low temperatures because of two problems. The first problem is the extreme sensitivity of the low-temperature observables to details of potential energy surfaces (PESs) parametrizing the nuclear Schrödinger equation. The second problem is the large size of the basis sets required for the numerical integration of the Schrödinger equation for strongly interacting molecules in the presence of fields, which precludes the application of rigorous quantum theory to all but a few atom-molecule systems. Here, we show that, if the scattering problem is formulated as a probabilistic prediction, quantum theory can provide reliable results with exponentially reduced numerical effort. Specifically, we show that the probability distributions that an observable is in a certain range of values can be obtained by averaging the results of scattering calculations with much smaller basis sets than required for calculations of individual scattering cross sections. Moreover, we show that such distributions do not rely on the precise knowledge of the PES. This opens the possibility of making probabilistic predictions of experimentally relevant observables for a wide variety of molecular systems, currently considered out of reach of quantum dynamics theory. We demonstrate the approach by computing the probability for elastic scattering of CaH and SrOH molecules by Li atoms and SrF molecules by Rb atoms.
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Affiliation(s)
- Masato Morita
- Department of Physics, University of Nevada, Reno, Nevada 89557, USA
| | - Roman V Krems
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - Timur V Tscherbul
- Department of Physics, University of Nevada, Reno, Nevada 89557, USA
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Wójcik P, Korona T, Tomza M. Interactions of benzene, naphthalene, and azulene with alkali-metal and alkaline-earth-metal atoms for ultracold studies. J Chem Phys 2019; 150:234106. [PMID: 31228913 DOI: 10.1063/1.5094907] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We consider collisional properties of polyatomic aromatic hydrocarbon molecules immersed into ultracold atomic gases and investigate intermolecular interactions of exemplary benzene, naphthalene, and azulene with alkali-metal (Li, Na, K, Rb, and Cs) and alkaline-earth-metal (Mg, Ca, Sr, and Ba) atoms. We apply the state-of-the-art ab initio techniques to compute the potential energy surfaces (PESs). We use the coupled cluster method restricted to single, double, and noniterative triple excitations to reproduce the correlation energy and the small-core energy-consistent pseudopotentials to model the scalar relativistic effects in heavier metal atoms. We also report the leading long-range isotropic and anisotropic dispersion and induction interaction coefficients. The PESs are characterized in detail, and the nature of intermolecular interactions is analyzed and benchmarked using symmetry-adapted perturbation theory. The full three-dimensional PESs are provided for the selected systems within the atom-bond pairwise additive representation and can be employed in scattering calculations. The present study of the electronic structure is the first step toward the evaluation of prospects for sympathetic cooling of polyatomic aromatic molecules with ultracold atoms. We suggest azulene, an isomer of naphthalene which possesses a significant permanent electric dipole moment and optical transitions in the visible range, as a promising candidate for electric field manipulation and buffer-gas or sympathetic cooling.
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Affiliation(s)
- Paweł Wójcik
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Tatiana Korona
- Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland
| | - Michał Tomza
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
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19
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Xu S, Xia M, Yin Y, Gu R, Xia Y, Yin J. Determination of the normal A 2Π state in MgF with application to direct laser cooling of molecules. J Chem Phys 2019; 150:084302. [PMID: 30823751 DOI: 10.1063/1.5083898] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report high resolution electronic spectroscopy of cold magnesium monofluoride (MgF) molecules in the gas phase, which are created by a combination of laser ablation, chemical reaction, and 6 K helium buffer-gas cooling. Thanks to the sufficient population in the low-lying rotational states, the P, Q, and R branches in the electronic transition of the X2Σ+ to A2Π state are able to be measured unambiguously by in-cell absorption spectra. For the first time, we show that the A2Π state of MgF is actually a normal state, not an inverted one. The laser cooling relevant transitions X2Σ+v=0,1,N=1→A2Π1/2(v=0,J'=1/2) are also identified, along with the hyperfine structure of the X2Σ+(v = 0, N = 1) state. This study provides an important step for ongoing laser cooling experiments of MgF molecules.
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Affiliation(s)
- Supeng Xu
- State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200062, China
| | - Meng Xia
- State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200062, China
| | - Yanning Yin
- State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200062, China
| | - Ruoxi Gu
- State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200062, China
| | - Yong Xia
- State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200062, China
| | - Jianping Yin
- State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200062, China
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20
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Cremers T, Janssen N, Sweers E, van de Meerakker SYT. Design and construction of a multistage Zeeman decelerator for crossed molecular beams scattering experiments. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2019; 90:013104. [PMID: 30709220 DOI: 10.1063/1.5066062] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 12/13/2018] [Indexed: 06/09/2023]
Abstract
Zeeman deceleration is a relatively new technique used to obtain full control over the velocity of paramagnetic atoms or molecules in a molecular beam. We present a detailed description of a multistage Zeeman decelerator that has recently become operational in our laboratory [Cremers et al., Phys. Rev. A 98, 033406 (2018)] and that is specifically optimized for crossed molecular beams scattering experiments. The decelerator consists of an alternating array of 100 solenoids and 100 permanent hexapoles to guide or decelerate beams of paramagnetic atoms or molecules. The Zeeman decelerator features a modular design that is mechanically easy to extend to arbitrary length and allows for solenoid and hexapole elements that are convenient to replace. The solenoids and associated electronics are efficiently water cooled and allow the Zeeman decelerator to operate at repetition rates exceeding 10 Hz. We characterize the performance of the decelerator using various beams of metastable rare gas atoms. Imaging of the atoms that exit the Zeeman decelerator reveals the transverse focusing properties of the hexapole array in the Zeeman decelerator.
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Affiliation(s)
- Theo Cremers
- Institute for Molecules and Materials, Radboud University, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Niek Janssen
- Institute for Molecules and Materials, Radboud University, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Edwin Sweers
- Institute for Molecules and Materials, Radboud University, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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Grzesiak J, Vashishta M, Djuricanin P, Stienkemeier F, Mudrich M, Dulitz K, Momose T. Production of rotationally cold methyl radicals in pulsed supersonic beams. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:113103. [PMID: 30501335 DOI: 10.1063/1.5052017] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Accepted: 10/16/2018] [Indexed: 06/09/2023]
Abstract
We present a comparison of two technically distinct methods for the generation of rotationally cold, pulsed supersonic beams of methyl radicals (CH3): a plate discharge source operating in the glow regime and a dielectric barrier discharge source. The results imply that the efficiency of both sources is comparable and that molecular beams with similar translational and rotational temperatures are formed. Methane (CH4) proved to be the most suitable radical precursor species.
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Affiliation(s)
- Jonas Grzesiak
- Physikalisches Institut, Universität Freiburg, 79104 Freiburg, Germany
| | - Manish Vashishta
- Department of Chemistry, The University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - Pavle Djuricanin
- Department of Chemistry, The University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | | | - Marcel Mudrich
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
| | - Katrin Dulitz
- Physikalisches Institut, Universität Freiburg, 79104 Freiburg, Germany
| | - Takamasa Momose
- Department of Chemistry, The University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
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22
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McCarron DJ, Steinecker MH, Zhu Y, DeMille D. Magnetic Trapping of an Ultracold Gas of Polar Molecules. PHYSICAL REVIEW LETTERS 2018; 121:013202. [PMID: 30028161 DOI: 10.1103/physrevlett.121.013202] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Indexed: 06/08/2023]
Abstract
We demonstrate the efficient transfer of molecules from a magneto-optical trap into a conservative magnetic quadrupole trap. Our scheme begins with a blue-detuned optical molasses to cool SrF molecules to ≈50 μK. Next, we optically pump the molecules into a strongly trapped sublevel. This two-step process reliably transfers ≈40% of the molecules initially trapped in the magneto-optical trap into a single quantum state in the magnetic trap. Once loaded, the molecule cloud is compressed by increasing the magnetic field gradient. We observe a magnetic trap lifetime of over 1 s. This opens a promising new path to study ultracold molecular collisions, and potentially to produce quantum-degenerate molecular gases via sympathetic cooling with co-trapped atoms.
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Affiliation(s)
- D J McCarron
- Department of Physics, Yale University, P.O. Box 208120, New Haven, Connecticut 06520, USA
| | - M H Steinecker
- Department of Physics, Yale University, P.O. Box 208120, New Haven, Connecticut 06520, USA
| | - Y Zhu
- Department of Physics, Yale University, P.O. Box 208120, New Haven, Connecticut 06520, USA
| | - D DeMille
- Department of Physics, Yale University, P.O. Box 208120, New Haven, Connecticut 06520, USA
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23
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Williams HJ, Caldwell L, Fitch NJ, Truppe S, Rodewald J, Hinds EA, Sauer BE, Tarbutt MR. Magnetic Trapping and Coherent Control of Laser-Cooled Molecules. PHYSICAL REVIEW LETTERS 2018; 120:163201. [PMID: 29756945 DOI: 10.1103/physrevlett.120.163201] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Indexed: 06/08/2023]
Abstract
We demonstrate coherent microwave control of the rotational, hyperfine, and Zeeman states of ultracold CaF molecules, and the magnetic trapping of these molecules in a single, selectable quantum state. We trap about 5×10^{3} molecules for almost 2 s at a temperature of 70(8) μK and a density of 1.2×10^{5} cm^{-3}. We measure the state-specific loss rate due to collisions with background helium.
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Affiliation(s)
- H J Williams
- Centre for Cold Matter, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom
| | - L Caldwell
- Centre for Cold Matter, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom
| | - N J Fitch
- Centre for Cold Matter, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom
| | - S Truppe
- Centre for Cold Matter, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom
| | - J Rodewald
- Centre for Cold Matter, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom
| | - E A Hinds
- Centre for Cold Matter, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom
| | - B E Sauer
- Centre for Cold Matter, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom
| | - M R Tarbutt
- Centre for Cold Matter, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom
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24
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Kozyryev I, Baum L, Aldridge L, Yu P, Eyler EE, Doyle JM. Coherent Bichromatic Force Deflection of Molecules. PHYSICAL REVIEW LETTERS 2018; 120:063205. [PMID: 29481281 DOI: 10.1103/physrevlett.120.063205] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Indexed: 06/08/2023]
Abstract
We demonstrate the effect of the coherent optical bichromatic force on a molecule, the polar free radical strontium monohydroxide (SrOH). A dual-frequency retroreflected laser beam addressing the X[over ˜]^{2}Σ^{+}↔A[over ˜]^{2}Π_{1/2} electronic transition coherently imparts momentum onto a cryogenic beam of SrOH. This directional photon exchange creates a bichromatic force that transversely deflects the molecules. By adjusting the relative phase between the forward and counterpropagating laser beams we reverse the direction of the applied force. A momentum transfer of 70ℏk is achieved with minimal loss of molecules to dark states. Modeling of the bichromatic force is performed via direct numerical solution of the time-dependent density matrix and is compared with experimental observations. Our results open the door to further coherent manipulation of molecular motion, including the efficient optical deceleration of diatomic and polyatomic molecules with complex level structures.
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Affiliation(s)
- Ivan Kozyryev
- Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Louis Baum
- Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Leland Aldridge
- Department of Physics, University of Connecticut, Storrs, Connecticut 06269, USA
| | - Phelan Yu
- Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Edward E Eyler
- Department of Physics, University of Connecticut, Storrs, Connecticut 06269, USA
| | - John M Doyle
- Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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25
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Wu X, Gantner T, Koller M, Zeppenfeld M, Chervenkov S, Rempe G. A cryofuge for cold-collision experiments with slow polar molecules. Science 2017; 358:645-648. [DOI: 10.1126/science.aan3029] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 08/07/2017] [Accepted: 09/25/2017] [Indexed: 11/02/2022]
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