Note: A modular and robust continuous supersonic expansion discharge source

Crabtree, Kyle N.; Kauffman, Carrie A.; McCall, Benjamin J.

doi:10.1063/1.3478019

Cited by 6 publications

(8 citation statements)

References 26 publications

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“…The design of the continuous gas-flow supersonic expansion source has been described in detail in an earlier publication. 22 While the cathode used in this work retains the dimensions and shape described there (a trumpet-flared pinhole with 1.0 mm starting and 2.4 mm ending inner diameters), it has been replaced by one machined from tungsten (previously stainless steel) in the hope of further improving the lifetime of the source. It has been found previously that the density of H + 3 ions produced varies with current supplied to the source (10 10 −10 12 cm −3 for 30−120 mA), and HN + 2 is expected to be formed in similar quantities in a predominantly hydrogen expansion.…”

Section: Methodsmentioning

confidence: 99%

“…Cryogenic ion traps have demonstrated the ability to cool molecular ions to very low temperatures. 15 Cooled molecular ions have also been produced by coupling electric discharges to supersonic expansions, achieving rotational temperatures on the order of 10 K. [16][17][18][19][20][21][22] In addition to producing cold molecular ions, these sources have the unique ability to efficiently produce ions that other ion sources cannot, including primary and cluster ions.…”

Section: Introductionmentioning

confidence: 99%

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Mid-infrared concentration-modulated noise-immune cavity-enhanced optical heterodyne molecular spectroscopy of a continuous supersonic expansion discharge source

Talicska

Porambo

Perry

et al. 2016

Review of Scientific Instruments

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Concentration-modulated noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) is implemented for the first time on a continuous gas-flow pinhole supersonic expansion discharge source for the study of cooled molecular ions. The instrument utilizes a continuous-wave optical parametric oscillator easily tunable from 2.5 to 3.9 μm and demonstrates a noise equivalent absorption of ∼1 × 10(-9) cm(-1). The effectiveness of concentration-modulated NICE-OHMS is tested through the acquisition of transitions in the ν1 fundamental band of HN2 (+) centered near 3234 cm(-1), with a signal-to-noise of ∼40 obtained for the strongest transitions. The technique is used to characterize the cooling abilities of the supersonic expansion discharge source itself, and a Boltzmann analysis determines a rotational temperature of ∼29 K for low rotational states of HN2 (+). Further improvements are discussed that will enable concentration-modulated NICE-OHMS to reach its full potential for the detection of molecular ions formed in supersonic expansion discharges.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mid-infrared concentration-modulated noise-immune cavity-enhanced optical heterodyne molecular spectroscopy of a continuous supersonic expansion discharge source

Talicska

Porambo

Perry

et al. 2016

Review of Scientific Instruments

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“…Finally, it is expected that a continuous supersonic expansion discharge source 20 and skimmer will replace the cold cathode ion source in the near future. The use of a supersonic expansion will enable the spectroscopy of larger and more fluxional molecular ions (e.g., CH + 5 and C 3 H + 3 ), for which quantum dilution at higher rotational temperatures has complicated previous attempts to apply velocity modulation spectroscopy.…”

Section: Discussionmentioning

confidence: 99%

“…20 To utilize such a source, our ion source chamber was designed to be large in size, and to couple to a high-throughput Roots pumping system through large-diameter tubing. However, for the initial testing of the instrument described here, we have designed a modular cold cathode discharge source for simplicity.…”

Section: B Ion Sourcementioning

confidence: 99%

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Ultra-sensitive high-precision spectroscopy of a fast molecular ion beam

Mills

Siller

Porambo

et al. 2011

The Journal of Chemical Physics

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Direct spectroscopy of a fast molecular ion beam offers many advantages over competing techniques, including the generality of the approach to any molecular ion, the complete elimination of spectral confusion due to neutral molecules, and the mass identification of individual spectral lines. The major challenge is the intrinsic weakness of absorption or dispersion signals resulting from the relatively low number density of ions in the beam. Direct spectroscopy of an ion beam was pioneered by Saykally and co-workers in the late 1980s, but has not been attempted since that time. Here, we present the design and construction of an ion beam spectrometer with several improvements over the Saykally design. The ion beam and its characterization have been improved by adopting recent advances in electrostatic optics, along with a time-of-flight mass spectrometer that can be used simultaneously with optical spectroscopy. As a proof of concept, a noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) setup with a noise equivalent absorption of ∼2 × 10 −11 cm −1 Hz −1/2 has been used to observe several transitions of the Meinel 1-0 band of N + 2 with linewidths of ∼120 MHz. An optical frequency comb has been used for absolute frequency calibration of transition frequencies to within ∼8 MHz. This work represents the first direct spectroscopy of an electronic transition in an ion beam, and also represents a major step toward the development of routine infrared spectroscopy of rotationally cooled molecular ions.

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Infrared Spectroscopy of Ions of Astrophysical Interest

Doménech

2018

Laboratory Astrophysics

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Molecular ions are key species in the chemistry of the interstellar medium (ISM). Given the low temperatures and number densities typically occurring in the ISM, one of the few available mechanisms to form more complex molecules is through barrierless exothermic reactions, as it is the case for many ion-molecule reactions. Ions are highly reactive species but they can be formed efficiently in the ISM by cosmic-ray or ultraviolet ionization and can survive for relatively long times due to the few collisions they suffer. On earth, molecular ions are "exotic" species much more difficult to produce in appreciable quantities. Electrical discharges in low pressure gases form cold plasmas which can be used to produce molecular ions in abundances high enough to enable their spectroscopic study.

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Note: A modular and robust continuous supersonic expansion discharge source

Cited by 6 publications

References 26 publications

Mid-infrared concentration-modulated noise-immune cavity-enhanced optical heterodyne molecular spectroscopy of a continuous supersonic expansion discharge source

Mid-infrared concentration-modulated noise-immune cavity-enhanced optical heterodyne molecular spectroscopy of a continuous supersonic expansion discharge source

Ultra-sensitive high-precision spectroscopy of a fast molecular ion beam

Infrared Spectroscopy of Ions of Astrophysical Interest

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