The Buffer Gas Beam: An Intense, Cold, and Slow Source for Atoms and Molecules

Hutzler, Nicholas R.; Lu, Hsin-I; Doyle, John M.

doi:10.1021/cr200362u

Cited by 358 publications

(414 citation statements)

References 170 publications

(640 reference statements)

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“…CBGBs can be used to produce high brightness and low velocity beams of nearly any small molecule [36]. Many molecules of the type under consideration, for example YbOH [26] and YbCCH [37], have been created in beams by ablating metal into an inert carrier gas mixed with a reactive gas like H 2 O 2 and HCCH, respectively, a technique commonly implemented in CBGBs as well.…”

Section: H Y S I C a L R E V I E W L E T T E R Smentioning

confidence: 99%

Precision Measurement of Time-Reversal Symmetry Violation with Laser-Cooled Polyatomic Molecules

2017

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Precision searches for time-reversal symmetry violating interactions in polar molecules are extremely sensitive probes of high energy physics beyond the standard model. To extend the reach of these probes into the PeV regime, long coherence times and large count rates are necessary. Recent advances in laser cooling of polar molecules offer one important tool-optical trapping. However, the types of molecules that have been laser cooled so far do not have the highly desirable combination of features for new physics searches, such as the ability to fully polarize and the existence of internal comagnetometer states. We show that by utilizing the internal degrees of freedom present only in molecules with at least three atoms, these features can be attained simultaneously with molecules that have simple structure and are amenable to laser cooling and trapping. DOI: 10.1103/PhysRevLett.119.133002 Precision measurements of heavy atomic and molecular systems have proven to be a powerful probe of high energy scales in the search for new physics beyond the standard model (BSM) [1]. For example, the limit on the electron's electric dipole moment (EDM), set by the ACME Collaboration using ThO, is sensitive to T-violating BSM physics at the ≳TeV scale [2]. This sensitivity relies on the ability to experimentally access the large effective electromagnetic fields (>10 GV=cm) present in heavy polar molecules by fully polarizing them in the laboratory frame. This makes the experimental challenges of working with such a complex species worth the effort.Despite the success of ACME, a current limitation of that experiment and all present molecular beam experiments is that their coherence time is limited to a few milliseconds by the beam transit time through an apparatus of reasonable size. Since EDM sensitivity scales linearly with coherence time, trapping neutral molecules has the potential to increase sensitivity by many orders of magnitude. Trapped molecular ions have shown great power in EDM searches [3], primarily due to their long coherence time of ∼1 s. Neutral species offer the ability to increase the number of trapped molecules much more easily and essentially without limit compared to ions, while retaining strong robustness against systematic errors. Here we show that laser-cooled and trapped polyatomic molecules offer a combination of features not available in other systems, including long lifetimes, robustness against systematic errors, and scalability, and present a feasible approach to access PeV-scale BSM physics.A very promising route to trapping EDM-sensitive molecules is direct laser cooling and trapping from cryogenic buffer gas beams (CBGBs), which has advanced tremendously in the last few years [4][5][6][7][8][9][10][11]. The molecules that have been cooled so far posses an electronic structure that makes them amenable to laser cooling, but also precludes the existence of Ω doublets, such as the 3 Δ 1 molecular state used in the two most sensitive electron EDM measurements [2,3]. These doublets enable full po...

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Section: H Y S I C a L R E V I E W L E T T E R Smentioning

confidence: 99%

Precision Measurement of Time-Reversal Symmetry Violation with Laser-Cooled Polyatomic Molecules

2017

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“…The corresponding mean free path l of the gas atoms lies in the range of * 0.05-1.5 mm (Haynes 2016). This corresponds to Knudsen numbers K n = l/d * 0.01-0.3, where d = 5 mm is the diameter of the exit aperture, placing the expansion in the intermediate to mildly supersonic continuum regime (Hutzler et al 2012). In this range, atoms and small molecules approach the regime of being fully accelerated by a buffer gas expansion (Hutzler et al 2012); however, the ''velocity slip'' phenomenon (Milani and Iannotta 1999) also becomes more and more pronounced as the mass of the diluted species increases.…”

Section: Appendix: Cluster Velocitiesmentioning

confidence: 99%

“…The terminal velocity for a gas mixture in the continuum expansion regime can be approximated (Cattolica et al 1979;Miller 1988) by the use of an average mass M ¼ P X i M i , so that for monatomic gases, one has v t ¼ 5k B T 0 = M ð Þ 1=2 [for a purely effusive expansion, the forward beam velocity is & 15% lower (Pauly 2000;Hutzler et al 2012)]. The aforementioned velocity of 2 nm particles is in sensible agreement with the value v t & 650 m/s obtained for a stagnation temperature T 0 = 200 K (as expected, this is somewhat higher than at the source jacket, see above), but the corresponding value for the 9 nm particle source parameters would be & 500 m/s, which is significantly greater than the measured velocity.…”

Section: Appendix: Cluster Velocitiesmentioning

confidence: 99%

Influence of source parameters on the growth of metal nanoparticles by sputter-gas-aggregation

Khojasteh

Kresin

2017

Appl Nanosci

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We describe the production of size-selected manganese nanoclusters using a magnetron sputtering/aggregation source. Since nanoparticle production is sensitive to a range of overlapping operating parameters (in particular, the sputtering discharge power, the inert gas flow rates, and the aggregation length), we focus on a detailed map of the influence of each parameter on the average nanocluster size. In this way, it is possible to identify the main contribution of each parameter to the physical processes taking place within the source. The discharge power and argon flow supply the metal vapor, and argon also plays a crucial role in the formation of condensation nuclei via three-body collisions. However, the argon flow and the discharge power have a relatively weak effect on the average nanocluster size in the exiting beam. Here the defining role is played by the source residence time, governed by the helium supply (which raises the pressure and density of the gas column inside the source, resulting in more efficient transport of nanoparticles to the exit) and by the aggregation path length.

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“…Typical parameters for the two sources have been well documented [1,29,30]. For our simulations, we chose parameters listed in Table. III, typical for a neon buffer-gas beam in the hydrodynamic expansion regime.…”

Section: Stark Deceleration Of a Position/velocity Correlated Beammentioning

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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The Buffer Gas Beam: An Intense, Cold, and Slow Source for Atoms and Molecules

Cited by 358 publications

References 170 publications

Precision Measurement of Time-Reversal Symmetry Violation with Laser-Cooled Polyatomic Molecules

Precision Measurement of Time-Reversal Symmetry Violation with Laser-Cooled Polyatomic Molecules

Influence of source parameters on the growth of metal nanoparticles by sputter-gas-aggregation

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

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