Pulsed Laval nozzle study of the kinetics of OH with unsaturated hydrocarbons at very low temperatures

Taylor, Sally; Goddard, A.; Blitz, Mark A.; Cleary, Patricia A.; Heard, Dwayne E.

doi:10.1039/b711411g

Cited by 60 publications

(71 citation statements)

References 53 publications

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“…We have used a pulsed Laval nozzle apparatus to study the kinetics and product formation for this reaction at 63 and 82 K. This method is described in detail elsewhere [29] (see Supplementary…”

Section: Methodsmentioning

confidence: 99%

Accelerated chemistry in the reaction between the hydroxyl radical and methanol at interstellar temperatures facilitated by tunnelling

et al. 2013

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Understanding the abundances of molecules observed in dense interstellar clouds requires knowledge of the rates of gas phase reactions between two neutral species. However, reactions possessing an activation barrier were considered too slow to play any important role at the low temperatures in these clouds. Here we show that despite the presence of a barrier the rate coefficient for the reaction between the hydroxyl radical (OH) and methanol, one of the most abundant organic molecules in space, is almost two orders of magnitude larger at 63K than previously measured at ~200K. We also observe formation of the methoxy radical product that was recently detected in space. These results are interpreted through the formation of a hydrogen-bonded complex that is sufficiently long-lived to undergo quantum mechanical tunnelling to form products. We postulate that this tunnelling

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Section: Methodsmentioning

confidence: 99%

Accelerated chemistry in the reaction between the hydroxyl radical and methanol at interstellar temperatures facilitated by tunnelling

et al. 2013

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“…The experimental setup of the pulsed Laval nozzle apparatus utilised in this study has been discussed in detail previously so only a brief description is given here [12][13][21][22] . Methanol was degassed and its vapour pressure was admitted to an evacuated cylinder where it was diluted with N 2 (Ar) and allowed to mix overnight before use.…”

Section: Plp-lif-laval Nozzlementioning

confidence: 99%

Low Temperature Kinetics of the CH₃OH + OH Reaction

et al. 2014

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The rate constant of the reaction between methanol and the hydroxyl radical has been studied in the temperature range 56-202 K by pulsed laser photolysis-laser induced fluorescence in two separate experiments using either a low temperature flow tube coupled to a time of flight mass spectrometer or a pulsed Laval nozzle apparatus. The two independent techniques yield rate constants which are in mutual agreement and consistent with the results reported previously below 82 K [Shannon et al., Nature Chemistry, 2013, 5, 745-749] and above 210 K [Dillon et al., Phys. Chem. Chem. 2005, 7, 349-355], showing a very sharp increase with decreasing temperature with an onset around 180 K. This onset is also signalled by strong chemiluminescence tentatively assigned to formaldehyde, which is consistent with the formation of the methoxy radical at low temperature by quantum tunnelling, and its subsequent reaction with H and OH. Our results add confidence to the previous low temperature rate constant measurements and consolidate the experimental reference dataset for further theoretical work required to describe quantitatively the tunnelling mechanism operating in this reaction. An additional measurement of the rate constant at 56 K yielded a value of (4.9 ± 0.8) × 10 −11 cm 3 molecule −1 s −1 (2σ), showing that the rate constant is increasing less rapidly at temperatures below 70 K.

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“…Instead it will be floating around in the gas cell, until it is randomly extracted with the He buffer gas. From Laval-nozzle theory [28], the gas flow through the nozzle Φ He is known to be 1.70 · 10 20 He atoms per second at 40 mbar cell pressure. Comparing this to the absolute number of He atoms in the stopping cell N He = 1.60 · 10 22 leads to the fraction of extracted atoms per second λ extr = Φ He /N He = 0.0106 s −1 .…”

Section: The Special Case Of 220 Rnmentioning

confidence: 99%

Determination of the extraction efficiency for 233U source α-recoil ions from the MLL buffer-gas stopping cell

2015

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Abstract. Following the α decay of 233 U, 229 Th recoil ions are shown to be extracted in a significant amount from the MLL buffer-gas stopping cell. The produced recoil ions and subsequent daughter nuclei are mass purified with the help of a customized quadrupole mass spectrometer. The combined extraction and mass-purification efficiency for 229 Th 3+ is determined via MCP-based measurements and via the direct detection of the 229 Th α decay. A large value of (10 ± 2)% for the combined extraction and mass-purification efficiency of 229 Th 3+ is obtained at a mass resolution of about 1 u/e. In addition to 229 Th, also other α-recoil ions of the 233,232 U decay chains are addressed.PACS. 27.90.+b A≥220 -23.60.+e α decay -07.75.+h mass spectrometers -23.35.+g isomer decay

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Pulsed Laval nozzle study of the kinetics of OH with unsaturated hydrocarbons at very low temperatures

Cited by 60 publications

References 53 publications

Accelerated chemistry in the reaction between the hydroxyl radical and methanol at interstellar temperatures facilitated by tunnelling

Accelerated chemistry in the reaction between the hydroxyl radical and methanol at interstellar temperatures facilitated by tunnelling

Low Temperature Kinetics of the CH₃OH + OH Reaction

Determination of the extraction efficiency for 233U source α-recoil ions from the MLL buffer-gas stopping cell

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Pulsed Laval nozzle study of the kinetics of OH with unsaturated hydrocarbons at very low temperatures

Cited by 60 publications

References 53 publications

Accelerated chemistry in the reaction between the hydroxyl radical and methanol at interstellar temperatures facilitated by tunnelling

Accelerated chemistry in the reaction between the hydroxyl radical and methanol at interstellar temperatures facilitated by tunnelling

Low Temperature Kinetics of the CH3OH + OH Reaction

Determination of the extraction efficiency for 233U source α-recoil ions from the MLL buffer-gas stopping cell

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Low Temperature Kinetics of the CH₃OH + OH Reaction