Production of cold bromine atoms at zero mean velocity by photodissociation

Doherty, William; Bell, Martin T.; Softley, T. P.; Rowland, Adrian M.; Wrede, Eckart; Carty, David

doi:10.1039/c0cp02472d

Cited by 13 publications

(18 citation statements)

References 43 publications

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“…However, Doherty et al [17] have recently used the PhotoStop approach [18] to trap Br atoms below 1 K at number densities up to 10 8 cm −3 . In addition, halogen atoms may be amenable to Zeeman deceleration [19].…”

Section: Introductionmentioning

confidence: 99%

Sympathetic cooling of fluorine atoms with ultracold atomic hydrogen

González-Martínez

Hutson²

2013

Phys. Rev. A

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. We consider the prospect of using ultracold hydrogen atoms for sympathetic cooling of fluorine atoms to microkelvin temperatures. We carry out quantum-mechanical calculations on collisions between cold F and H atoms in magnetically trappable states and show that the ratio of elastic to inelastic cross sections remains high across a wide range of temperatures and magnetic fields. For F atoms initially in the spin-stretched state ( 2 P 3/2 , f = m f = +2), sympathetic cooling appears likely to succeed from starting temperatures around 1 K or even higher. This occurs because inelastic collisions are suppressed by p-wave and d-wave barriers that are 600 mK and 3.2 K high, respectively. In combination with recent results on H + NH and H + OH collisions [M. L. González-Martínez and J. M. Hutson, Phys. Rev. Lett. 111, 203004 (2013)], this establishes ultracold H atoms as a very promising and versatile coolant for atoms and molecules that cannot be laser-cooled.

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Section: Introductionmentioning

confidence: 99%

Sympathetic cooling of fluorine atoms with ultracold atomic hydrogen

González-Martínez

Hutson²

2013

Phys. Rev. A

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“…produces one ground state Br( 2 P 3/2 ) and one spin-orbit excited Br( 2 P 1/2 ) atom. As shown previously, the centerof-mass frame recoil velocity of the Br fragments u Br is [6] …”

Section: Introductionmentioning

confidence: 98%

“…We have previously demonstrated the production of cold Br atoms in the photodissociation of Br 2 [6], and confinement of the groundstate atoms in a permanent-magnet trap for durations up * tim.softley@chem.ox.ac.uk to 99 ms [7]. Permanent magnetic traps can provide larger trap depths for confinement of cold atoms than those produced by non-superconducting electromagnetic coils [8], which are limited to a trap depth of few thousand gauss.…”

Section: Introductionmentioning

confidence: 99%

“…In order to distinguish the signal of interest, a mechanical shutter is used to block the photodissociation laser, and the one-color probe laser signal is recorded separately in alternation with the two-color signal. The decay of the trapped Br atoms is mapped by delaying the probe laser with respect to the gas pulse [6]. Ionization of the Br 2 parent molecules does not contribute to the recorded signal, as the wavelength used in the REMPI detection was far from resonance with the 2 + 1 REMPI transition of Br 2 at 263 nm [10].…”

Section: Introductionmentioning

confidence: 99%

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Collisional trap losses of cold magnetically trapped Br atoms

2014

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Near-threshold photodissociation of Br2 from a supersonic beam produces slow bromine atoms that are trapped in the magnetic field minimum formed between two opposing permanent magnets. Here, we quantify the dominant trap loss rate due to collisions with two sources of residual gas: the background limited by the vacuum chamber base pressure, and the carrier gas during the supersonic gas pulse. The loss rate due to collisions with residual Ar in the background follows pseudo firstorder kinetics, and the bimolecular rate coefficient for collisional loss from the trap is determined by measurement of this rate as a function of the background Ar pressure. This rate coefficient is smaller than the total elastic collision rate coefficient, as it only samples those collisions that lead to trap loss, and is determined to be νσ = (1.12±0.09)×10 −9 cm 3 s −1 . The calculated differential cross section can be used with this value to estimate a trap depth of 293 ± 24 mK. Carrier gas collisions occur only during the tail of the supersonic beam pulse. Using the differential cross section verified by the background-gas collision measurements provides an estimate of the peak molecular beam density of (3.0 ± 0.3) × 10 13 cm −3 in good agreement with the prediction of a simple supersonic expansion model. Finally, we estimate the trap loss rate due to Majorana transitions to be negligible, owing to the relatively large trapped-atom phase-space volume.

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“…The photostop method is capable of loading traps by producing the cold molecules directly inside the trap. This has been demonstrated with atomic bromine 20 in a permanent magnetic trap. 21 Following on from our work on the production of cold NO via photostop, 22 we demonstrate that cold SH radicals can be magnetically trapped following the photodissociation of H 2 S in a molecular-beam.…”

Section: Introductionmentioning

confidence: 99%

Magnetic trapping of SH radicals

Eardley

Warner

Deng

et al. 2017

Phys. Chem. Chem. Phys.

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. The molecular-beam speed was controlled by the mixing ratio of H2S in Kr to match the recoil velocity of the SH photofragments such that some SH radicals were produced with near-zero laboratory-frame velocity. The density of SH radicals in the 2 Π 3/2 , v = 0, J = 3/2 state was followed by (2+1) REMPI over seven orders of magnitude of signal intensity.5 ms after photodissociation, SH radicals moving faster than the capture velocity of 13 m/s had left the trap. The 1/e trap lifetime of the remaining SH radicals was 40 ± 10 ms at an estimated density of 5×10 4 molecules/cm 3 . Photostop offers a simple and direct way to accumulate absolute ground state molecules in a variety of traps.

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Production of cold bromine atoms at zero mean velocity by photodissociation

Cited by 13 publications

References 43 publications

Sympathetic cooling of fluorine atoms with ultracold atomic hydrogen

Sympathetic cooling of fluorine atoms with ultracold atomic hydrogen

Collisional trap losses of cold magnetically trapped Br atoms

Magnetic trapping of SH radicals

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