State purity of decelerated molecular beams

Fitch, N. J.; Esteves, D.; Fabrikant, Maya; Briles, Travis; Shyur, Yomay; Parazzoli, L. P.; Lewandowski, H. J.

doi:10.1016/j.jms.2012.07.005

Cited by 11 publications

(10 citation statements)

References 50 publications

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“…TheB 1 E (v 2 = 5) ←X(v 2 = 0, upper inversion doublet) transition is selected because the predissociation rate of the intermediateB state is independent of the rotational state of the molecule. Fitch et al have utilized thisB ←X transition in their characterization of a Stark-decelerated ND 3 beam, 23 as have Bertsche and Osterwalder 24,25 in their study of hexapole-guided ND 3 from an effusive 300 K source. In related experiments, Putzke et al 26 used fluorescence excitation spectroscopy to characterize the rotational distribution of a supersonic beam of benzonitrile transmitted through a straight AC electric quadrupole guide.…”

Section: A Simulation Of Rempi Spectra To Extract Rotational Level Pmentioning

confidence: 99%

Production of cold beams of ND3 with variable rotational state distributions by electrostatic extraction of He and Ne buffer-gas-cooled beams

Twyman

Bell

Heazlewood

2014

The Journal of Chemical Physics

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The measurement of the rotational state distribution of a velocity-selected, buffer-gas-cooled beam of ND3 is described. In an apparatus recently constructed to study cold ion-molecule collisions, the ND3 beam is extracted from a cryogenically cooled buffer-gas cell using a 2.15 m long electrostatic quadrupole guide with three 90° bends. (2+1) resonance enhanced multiphoton ionization spectra of molecules exiting the guide show that beams of ND3 can be produced with rotational state populations corresponding to approximately T(rot) = 9-18 K, achieved through manipulation of the temperature of the buffer-gas cell (operated at 6 K or 17 K), the identity of the buffer gas (He or Ne), or the relative densities of the buffer gas and ND3. The translational temperature of the guided ND3 is found to be similar in a 6 K helium and 17 K neon buffer-gas cell (peak kinetic energies of 6.92(0.13) K and 5.90(0.01) K, respectively). The characterization of this cold-molecule source provides an opportunity for the first experimental investigations into the rotational dependence of reaction cross sections in low temperature collisions.

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Section: A Simulation Of Rempi Spectra To Extract Rotational Level Pmentioning

confidence: 99%

Production of cold beams of ND3 with variable rotational state distributions by electrostatic extraction of He and Ne buffer-gas-cooled beams

Twyman

Bell

Heazlewood

2014

The Journal of Chemical Physics

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“…In addition, molecules in a decelerated CH beam could potentially be combined and trapped with magnetic or electric fields. This would enable the study of collisions down to energies in the 10-100 mK regime with essentially only one quantum state populated [16]. This paper describes experimental work investigating the production of CH in a cryogenic buffer-gas cell, and detailed calculations of the coupling of a cryogenic beam of CH to a traveling-wave Stark decelerator.…”

Section: Introductionmentioning

confidence: 99%

Method for traveling-wave deceleration of buffer-gas beams of CH

et al. 2014

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Cryogenic buffer-gas beams are a promising method for producing bright sources of cold molecular radicals for cold collision and chemical reaction experiments. In order to use these beams in studies of reactions with controlled collision energies, or in trapping experiments, one needs a method of controlling the forward velocity of the beam. A Stark decelerator can be an effective tool for controlling the mean speed of molecules produced by supersonic jets, but efficient deceleration of buffer-gas beams presents new challenges due to longer pulse lengths. Traveling-wave decelerators are uniquely suited to meet these challenges because of their ability to confine molecules in three dimensions during deceleration and their versatility afforded by the analog control of the electrodes. We have created ground state CH(X 2 Π) radicals in a cryogenic buffer-gas cell with the potential to produce a cold molecular beam of 10 11 mol./pulse. We present a general protocol for Stark deceleration of beams with a large position and velocity spread for use with a traveling-wave decelerator. Our method involves confining molecules transversely with a hexapole for an optimized distance before deceleration. This rotates the phase-space distribution of the molecular packet so that the packet is matched to the time varying phase-space acceptance of the decelerator. We demonstrate with simulations that this method can decelerate a significant fraction of the molecules in successive wells of a traveling-wave decelerator to produce energy-tuned beams for cold and controlled molecule experiments.

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“…[20,21] The technique described here would produce decelerated samples containing as mall number of states;for example, adecelerated beam of benzonitrile from a4Kb uffer gas source would contain significant populations of states j 7 70 i, j 6 60 i, j 5 50 i, j 4 40 i,a nd j 3 30 i.E xperimenters requiring higher state purity coulds electively pump trappedo rd eceleratingm olecules out of specifico ccupied states throughr esonant microwave fields. [20,21] The technique described here would produce decelerated samples containing as mall number of states;for example, adecelerated beam of benzonitrile from a4Kb uffer gas source would contain significant populations of states j 7 70 i, j 6 60 i, j 5 50 i, j 4 40 i,a nd j 3 30 i.E xperimenters requiring higher state purity coulds electively pump trappedo rd eceleratingm olecules out of specifico ccupied states throughr esonant microwave fields.…”

Section: Resultsmentioning

confidence: 99%

“…State purity in Stark-decelerated samples varies greatly with speciesa nd decelerator design. [20,21] The technique described here would produce decelerated samples containing as mall number of states;for example, adecelerated beam of benzonitrile from a4Kb uffer gas source would contain significant populations of states j 7 70 i, j 6 60 i, j 5 50 i, j 4 40 i,a nd j 3 30 i.E xperimenters requiring higher state purity coulds electively pump trappedo rd eceleratingm olecules out of specifico ccupied states throughr esonant microwave fields. Buffer-gas cooling has been shown to be an effective tool for cooling both vibrational and conformal degrees of freedom in many species, althoughv ibrations in light, stiff speciesh ave been observed to cool slowly.…”

Section: Resultsmentioning

confidence: 99%

Decelerating and Trapping Large Polar Molecules

Patterson

2016

ChemPhysChem

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Manipulating the motion of large polyatomic molecules, such as benzonitrile (C H CN), presents significant difficulties compared to the manipulation of diatomic molecules. Although recent impressive results have demonstrated manipulation, trapping, and cooling of molecules as large as CH F, no general technique for trapping such molecules has been demonstrated, and cold neutral molecules larger than 5 atoms have not been trapped (M. Zeppenfeld, B. G. U. Englert, R. Glöckner, A. Prehn, M. Mielenz, C. Sommer, L. D. van Buuren, M. Motsch, G. Rempe, Nature 2012, 491, 570-573). In particular, extending Stark deceleration and electrostatic trapping to such species remains challenging. Here, we propose to combine a novel "asymmetric doublet state" Stark decelerator with recently demonstrated slow, cold, buffer-gas-cooled beams of closed-shell volatile molecules to realize a general system for decelerating and trapping samples of a broad range of volatile neutral polar prolate asymmetric top molecules. The technique is applicable to most stable volatile molecules in the 100-500 AMU range, and would be capable of producing trapped samples in a single rotational state and at a motional temperature of hundreds of mK. Such samples would immediately allow for spectroscopy of unprecedented resolution, and extensions would allow for further cooling and direct observation of slow intramolecular processes such as vibrational relaxation and Hertz-level tunneling dynamics.

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State purity of decelerated molecular beams

Cited by 11 publications

References 50 publications

Production of cold beams of ND3 with variable rotational state distributions by electrostatic extraction of He and Ne buffer-gas-cooled beams

Production of cold beams of ND3 with variable rotational state distributions by electrostatic extraction of He and Ne buffer-gas-cooled beams

Method for traveling-wave deceleration of buffer-gas beams of CH

Decelerating and Trapping Large Polar Molecules

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