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Cheng C, van der Poel APP, Jansen P, Quintero-Pérez M, Wall TE, Ubachs W, Bethlem HL. Molecular Fountain. PHYSICAL REVIEW LETTERS 2016; 117:253201. [PMID: 28036190 DOI: 10.1103/physrevlett.117.253201] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Indexed: 06/06/2023]
Abstract
The resolution of any spectroscopic or interferometric experiment is ultimately limited by the total time a particle is interrogated. Here we demonstrate the first molecular fountain, a development which permits hitherto unattainably long interrogation times with molecules. In our experiments, ammonia molecules are decelerated and cooled using electric fields, launched upwards with a velocity between 1.4 and 1.9 m/s and observed as they fall back under gravity. A combination of quadrupole lenses and bunching elements is used to shape the beam such that it has a large position spread and a small velocity spread (corresponding to a transverse temperature of <10 μK and a longitudinal temperature of <1 μK) when the molecules are in free fall, while being strongly focused at the detection region. The molecules are in free fall for up to 266 ms, making it possible, in principle, to perform sub-Hz measurements in molecular systems and paving the way for stringent tests of fundamental physics theories.
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Affiliation(s)
- Cunfeng Cheng
- LaserLaB, Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Aernout P P van der Poel
- LaserLaB, Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Paul Jansen
- LaserLaB, Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Marina Quintero-Pérez
- LaserLaB, Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Thomas E Wall
- LaserLaB, Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Wim Ubachs
- LaserLaB, Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Hendrick L Bethlem
- LaserLaB, Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
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Meyer KAE, Pollum LL, Petralia LS, Tauschinsky A, Rennick CJ, Softley TP, Heazlewood BR. Ejection of Coulomb Crystals from a Linear Paul Ion Trap for Ion-Molecule Reaction Studies. J Phys Chem A 2015; 119:12449-56. [PMID: 26406306 DOI: 10.1021/acs.jpca.5b07919] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Coulomb crystals are being increasingly employed as a highly localized source of cold ions for the study of ion-molecule chemical reactions. To extend the scope of reactions that can be studied in Coulomb crystals-from simple reactions involving laser-cooled atomic ions, to more complex systems where molecular reactants give rise to multiple product channels-sensitive product detection methodologies are required. The use of a digital ion trap (DIT) and a new damped cosine trap (DCT) are described, which facilitate the ejection of Coulomb-crystallized ions onto an external detector for the recording of time-of-flight (TOF) mass spectra. This enables the examination of reaction dynamics and kinetics between Coulomb-crystallized ions and neutral molecules: ionic products are typically cotrapped, thus ejecting the crystal onto an external detector reveals the masses, identities, and quantities of all ionic species at a selected point in the reaction. Two reaction systems are examined: the reaction of Ca(+) with deuterated isotopologues of water, and the charge exchange between cotrapped Xe(+) with deuterated isotopologues of ammonia. These reactions are examples of two distinct types of experiment, the first involving direct reaction of the laser-cooled ions, and the second involving reaction of sympathetically-cooled heavy ions to form a mixture of light product ions. Extensive simulations are conducted to interpret experimental results and calculate optimal operating parameters, facilitating a comparison between the DIT and DCT approaches. The simulations also demonstrate a correlation between crystal shape and image shape on the detector, suggesting a possible means for determining crystal geometry for nonfluorescing ions.
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Affiliation(s)
- K A E Meyer
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory , 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom.,Institut für Physikalische Chemie, Georg-August-Universität Göttingen , Tammannstraße 6, D-37077 Göttingen, Germany
| | - L L Pollum
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory , 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - L S Petralia
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory , 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - A Tauschinsky
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory , 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - C J Rennick
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory , 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - T P Softley
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory , 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - B R Heazlewood
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory , 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
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Vogels SN, Gao Z, van de Meerakker SYT. Optimal beam sources for Stark decelerators in collision experiments: a tutorial review. EPJ TECHNIQUES AND INSTRUMENTATION 2015; 2:12. [PMID: 26269781 PMCID: PMC4527007 DOI: 10.1140/epjti/s40485-015-0021-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 07/07/2015] [Indexed: 06/04/2023]
Abstract
With the Stark deceleration technique, packets of molecules with a tunable velocity, a narrow velocity spread, and a high state purity can be produced. These tamed molecular beams find applications in high resolution spectroscopy, cold molecule trapping, and controlled scattering experiments. The quality and purity of the packets of molecules emerging from the decelerator critically depend on the specifications of the decelerator, but also on the characteristics of the molecular beam pulse with which the decelerator is loaded. We consider three frequently used molecular beam sources, and discuss their suitability for molecular beam deceleration experiments, in particular with the application in crossed beam scattering in mind. The performance of two valves in particular, the Nijmegen Pulsed Valve and the Jordan Valve, is illustrated by decelerating ND 3 molecules in a 2.6 meter-long Stark decelerator. We describe a protocol to characterize the valve, and to optimally load the pulse of molecules into the decelerator. We characterize the valves regarding opening time duration, optimal valve-to-skimmer distance, mean velocity, velocity spread, state purity, and relative intensity.
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Affiliation(s)
- Sjoerd N Vogels
- Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, AJ Nijmegen, 6525 Netherlands
| | - Zhi Gao
- Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, AJ Nijmegen, 6525 Netherlands
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Quintero-Pérez M, Jansen P, Wall TE, van den Berg JE, Hoekstra S, Bethlem HL. Static trapping of polar molecules in a traveling wave decelerator. PHYSICAL REVIEW LETTERS 2013; 110:133003. [PMID: 23581314 DOI: 10.1103/physrevlett.110.133003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2012] [Indexed: 06/02/2023]
Abstract
We present experiments on decelerating and trapping ammonia molecules using a combination of a Stark decelerator and a traveling wave decelerator. In the traveling wave decelerator, a moving potential is created by a series of ring-shaped electrodes to which oscillating high voltages (HV) are applied. By lowering the frequency of the applied voltages, the molecules confined in the moving trap are decelerated and brought to a standstill. As the molecules are confined in a true 3D well, this kind of deceleration has practically no losses, resulting in a great improvement on the usual Stark deceleration techniques. The necessary voltages are generated by amplifying the output of an arbitrary wave generator using fast HV amplifiers, giving us great control over the trapped molecules. We illustrate this by experiments in which we adiabatically cool trapped NH3 and ND3 molecules and resonantly excite their motion.
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Affiliation(s)
- Marina Quintero-Pérez
- LaserLaB, Department of Physics and Astronomy, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
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