Quantum rainbow scattering at tunable velocities

Strebel, M.; Müller, Tim-Oliver; Ruff, Bernhard; Stienkemeier, F.; Mudrich, M.

doi:10.1103/physreva.86.062711

Cited by 15 publications

(13 citation statements)

References 18 publications

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“…This renders them particularly suitable for studying low-energy collision dynamics [3,4,5,6,7,8,9,10] and enabling controlled chemistry [11,12]. Cold molecules are also beneficial for precision spectroscopy, serving as an important tool for exploring fundamental physics [13,14,15].…”

Section: Introductionmentioning

confidence: 99%

Thermometry of Guided Molecular Beams from a Cryogenic Buffer‐Gas Cell

Gantner

Zeppenfeld

et al. 2016

ChemPhysChem

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Abstract.We present a comprehensive characterization of cold molecular beams from a cryogenic buffer-gas cell, providing an insight into the physics of buffer-gas cooling. Cold molecular beams are extracted from a cryogenic cell by electrostatic guiding, which is also used to measure their velocity distribution. Molecules' rotational-state distribution is probed via radio-frequency resonant depletion spectroscopy. With the help of complete trajectory simulations, yielding the guiding efficiency for all of the thermally populated states, we are able to determine both the rotational and the translational temperature of the molecules at the output of the buffer-gas cell. This thermometry method is demonstrated for various regimes of buffer-gas cooling and beam formation as well as for molecular species of different sizes, CH 3 F and CF 3 CCH. Comparison between the rotational and translational temperatures provides evidence of faster rotational thermalization for the CH 3 F-He system in the limit of low He density. In addition, the relaxation rates for different rotational states appear to be different.2

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Section: Introductionmentioning

confidence: 99%

Thermometry of Guided Molecular Beams from a Cryogenic Buffer‐Gas Cell

Gantner

Zeppenfeld

et al. 2016

ChemPhysChem

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confidence: 75%

“…The ions are stored for a long time and their number can be accurately determined, which allows the study of reactions with rates as small as one per minute. In a similar fashion, collisions of slow beams of ammonia with magnetically trapped OH molecules were observed [23], as were collisions of slow beams of rare gas atoms and SF 6 with lithium in a magneto-optic trap [24].Here, we study collisions between neutral ammonia molecules stored in a synchrotron and beams of argon atoms. Using a synchrotron for collision studies offers two advantages: First, the collision partners move in the same direction as the stored molecules, resulting in a small relative velocity and thus a low collision energy.…”

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confidence: 78%

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Cold Collisions in a Molecular Synchrotron

Poel¹,

Zieger²,

Meerakker³

et al. 2018

Phys. Rev. Lett.

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We study collisions between neutral, deuterated ammonia molecules (ND 3 ) stored in a 50 cm diameter synchrotron and argon atoms in copropagating supersonic beams. The advantages of using a synchrotron in collision studies are twofold: (i) By storing ammonia molecules many round-trips, the sensitivity to collisions is greatly enhanced; (ii) the collision partners move in the same direction as the stored molecules, resulting in low collision energies. We tune the collision energy in three different ways: by varying the velocity of the stored ammonia packets, by varying the temperature of the pulsed valve that releases the argon atoms, and by varying the timing between the supersonic argon beam and the stored ammonia packets. These give consistent results. We determine the relative, total, integrated cross section for ND 3 þ Ar collisions in the energy range of 40-140 cm −1 , with a resolution of 5-10 cm −1 and an uncertainty of 7%-15%. Our measurements are in good agreement with theoretical scattering calculations. DOI: 10.1103/PhysRevLett.120.033402 The crossed molecular beam technique, pioneered by Herschbach and Lee, has yielded a detailed understanding of how molecules interact and react [1,2]. Until recently, these crossed molecular beam studies were limited by the velocities of the molecular beams to collision energies above a few hundred cm −1 (1 cm −1 ≃ 1.4 K). Over the past years, however, a number of ingenious methods [3][4][5] have been developed to study collisions in the cold regime. These advances are important for several reasons. First, the temperatures of interstellar clouds are typically between 10 and 100 K; collision data of simple molecules at low temperatures are thus highly relevant for understanding the chemistry in these clouds [6]. Furthermore, quantum effects become important at low temperatures, where few partial waves contribute and the de Broglie wavelength associated with the relative velocity becomes comparable to or larger than the intermolecular distances. Of particular interest are resonances of the collision cross section as a function of the collision energy [7][8][9][10]. The position and shape of these resonances are very sensitive to the exact shape of the PES and thus serve as precise tests of our understanding of intermolecular forces.The ability to control the velocity of molecules using time-varying electric fields has allowed studies of inelastic collisions of OH and NO molecules with rare gas atoms at low collision energies [11][12][13][14]. Using cryogenically cooled beams under a small (and variable) crossing angle, inelastic collisions of O 2 and CO with H 2 and helium at energies between 5 and 30 K have been studied [15]. Even lower temperatures can be obtained by using magnetic or electric guides to merge two molecular beams into a single beam. This technique has been used to study Penning ionization reactions of various atoms and molecules with metastable helium [16][17][18][19] and collisions between ground state hydrogen molecules and hydrogen molecules in ...

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“…A schematic drawing of the apparatus is shown in Figure 1. Some parts of the setup have already been described elsewhere [25][26][27] .…”

Section: A General Setupmentioning

confidence: 99%

Penning collisions between supersonically expanded metastable He atoms and laser-cooled Li atoms

Grzesiak

Momose

Stienkemeier

et al. 2019

The Journal of Chemical Physics

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We describe an experimental setup comprised of a discharge source for supersonic beams of metastable helium atoms and a magneto-optical trap (MOT) for ultracold lithium atoms that makes it possible to study Penning ionization and associative ionization processes at high ion count rates. The cationic reaction products are analyzed using a novel ion detection scheme which allows for mass selection, a high ion extraction efficiency and a good collision-energy resolution. The influence of elastic He-Li collisions on the steady-state Li atom number in the MOT is described, and the collision data are used to estimate the excitation efficiency of the discharge source. We also show that Penning collisions can be directly used to probe the temperature of the Li cloud without the need for an additional time-resolved absorption or fluorescence detection system.

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Quantum rainbow scattering at tunable velocities

Cited by 15 publications

References 18 publications

Thermometry of Guided Molecular Beams from a Cryogenic Buffer‐Gas Cell

Thermometry of Guided Molecular Beams from a Cryogenic Buffer‐Gas Cell

Cold Collisions in a Molecular Synchrotron

Penning collisions between supersonically expanded metastable He atoms and laser-cooled Li atoms

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