Absolute electron impact ionization cross-sections for the C1 to C4 alcohols

Hudson, James E.; Hamilton, Michelle L.; Vallance, Claire; Harland, Peter W.

doi:10.1039/b304456d

Cited by 71 publications

(119 citation statements)

References 21 publications

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“…6 we include the calculation of the total ionization cross section using the binary Born-Bethe (BEB) method [53,54]. The present results using the BEB model are in excellent agreement with the measurements of Hudson et al [55]. The measurements of Duric et al [56] and Rejoub et al [52] are in good accord with the present results except at the peak where the results of Duric et al [56] are slightly lower, while the results of Rejoub et al [52] are slightly higher than the present results.…”

Section: Resultssupporting

confidence: 80%

“…The measurements of Duric et al [56] and Rejoub et al [52] are in good accord with the present results except at the peak where the results of Duric et al [56] are slightly lower, while the results of Rejoub et al [52] are slightly higher than the present results. The BEB results of Hudson et al [55] are slightly higher compared to the present results, and this may be attributed to the difference in the parameters used in the calculation for ionization cross sections. The results of Deutsch et al [57] are shifted towards a lower energy compared to other results.…”

Section: Resultscontrasting

confidence: 54%

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Computation of electron-impact rotationally elastic total cross sections for methanol over an extensive range of impact energy (0.1 – 2000 eV)

Vinodkumar¹,

Limbachiya²,

Barot³

et al. 2013

Phys. Rev. A

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Theoretical rotationally elastic total cross sections for electron scattering from methanol over the incident energy range 0.1-2000 eV are presented. The computation of such cross sections for methanol is reported over such an extended energy range. We have employed two distinct formalisms to compute the cross sections across this energy range; between 0.1 eV and the ionization threshold of the target we have used the ab initio R-matrix method, while at higher energies the spherical complex optical potential method is invoked. The results from both formalisms match quite well at energies where they overlap and hence imply that they are consistent with each other. These total cross-section results are also in very good agreement with available experimental data and earlier theoretical data. The composite methodology employed here is well established and can be used to predict cross sections for other targets where data is scarce or not available.

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Section: Resultssupporting

confidence: 80%

Section: Resultscontrasting

confidence: 54%

Computation of electron-impact rotationally elastic total cross sections for methanol over an extensive range of impact energy (0.1 – 2000 eV)

Vinodkumar¹,

Limbachiya²,

Barot³

et al. 2013

Phys. Rev. A

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“…where φ is the fragmentation fraction of CO and methanol at a specific mass, σ the total electron impact ionisation cross section of CO (or methane) and methanol at 70 eV and A the integrated QMS signal of CO or methanol. σ CO is given as 2.44Å 2 (Hudson et al 2004) and σ methanol is 4.44Å 2 (Hudson et al 2003). For methane it is 3.93Å 2 (Nishimura & Tawara 1994).…”

Section: Methanol Co-desorption Rate Determinationmentioning

confidence: 99%

Methanol ice co-desorption as a mechanism to explain cold methanol in the gas-phase

Ligterink

Walsh

Bhuin

et al. 2018

A&A

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Context. Methanol is formed via surface reactions on icy dust grains. Methanol is also detected in the gas-phase at temperatures below its thermal desorption temperature and at levels higher than can be explained by pure gas-phase chemistry. The process that controls the transition from solid state to gas-phase methanol in cold environments is not understood. Aims. The goal of this work is to investigate whether thermal CO desorption provides an indirect pathway for methanol to co-desorb at low temperatures. Methods. Mixed CH 3 OH:CO/CH 4 ices were heated under UHV (ultra-high vacuum) conditions and ice contents are traced using RAIRS (reflection absorption IR spectroscopy), while desorbing species were detected mass spectrometrically. An updated gas-grain chemical network was used to test the impact of the results of these experiments. The physical model used is applicable for TW Hya, a protoplanetary disk in which cold gas-phase methanol has recently been detected. Results. Methanol release together with thermal CO desorption is found to be an ineffective process in the experiments, resulting in an upper limit of ≤ 7.3 × 10 −7 CH 3 OH molecules per CO molecule over all ice mixtures considered. Chemical modelling based on the upper limits shows that co-desorption rates as low as 10 −6 CH 3 OH molecules per CO molecule are high enough to release substantial amounts of methanol to the gas-phase at and around the location of the CO thermal desorption front in a protoplanetary disk. The impact of thermal co-desorption of CH 3 OH with CO as a grain-gas bridge mechanism is compared with that of UV induced photodesorption and chemisorption.

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“…In order to compare GA, EG and MF yields, the desorption QMS signals are integrated, then normalized to the total column density of the most abundant carbon-bearing species observed by RAIRS at the end of the co-deposition (see Fedoseev et al 2015;Chuang et al 2016). Then, the obtained values for GA, EG and MF are calibrated using the available literature ionisation cross-section values (Hudson et al 2003(Hudson et al , 2006Bull & Harland 2008). The uncertainty in the abundance determination is statistically derived by averaging the result from a number of identical experiments.…”

Section: Experimental Methodsmentioning

confidence: 99%

Production of complex organic molecules:H-atom addition versus UV irradiation

Chuang

Fedoseev

Qasim

et al. 2017

Mon. Not. R. Astron. Soc.

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AB S TRAC TComplex organic molecules (COMs) have been identified in different environments in starforming regions. Laboratory studies show that COMs form in the solid state, on icy grains, typically following a 'non-energetic' (atom-addition) or 'energetic' (UV-photon absorption) trigger. So far, such studies have been largely performed for single processes. Here, we present the first work that quantitatively investigates both the relative importance and the cumulative effect of '(non-)energetic' processing. We focus on astronomically relevant CO:CH3OH = 4:1 ice analogues exposed to doses relevant for the collapse stage of dense clouds. Hydrogenation experiments result in the formation of methyl formate (MF; HC(O)OCH3), glycolaldehyde (GA; HC(O)CH2OH) and ethylene glycol (EG; H2C(OH)CH2OH) at 14 K. The absolute abundances and the abundance fractions are found to be dependent on the H-atom/CO:CH3 OHmolecule ratios and on the overall deposition rate. In the case that ices are exposed to UV photons only, several different COMs are found. Typically, the abundance fractions are 0.2 for MF, 0.3 for GA and 0.5 for EG as opposed to the values found in pure hydrogenation experiments without UV in which MF is largely absent: 0.0, 0.2-0.6 and 0.8-0.4, respectively. In experiments where both are applied, overall COM abundances drop to about half of those found in the pure UV irradiation experiments, but the composition fractions are very similar. This implies COM ratios can be used as a diagnostic tool to derive the processing history of an ice. Solid-state branching ratios derived here for GA and EG compare well with observations, while the MF case cannot be explained by solid-state conditions investigated here.

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Absolute electron impact ionization cross-sections for the C1 to C4 alcohols

Cited by 71 publications

References 21 publications

Computation of electron-impact rotationally elastic total cross sections for methanol over an extensive range of impact energy (0.1 – 2000 eV)

Computation of electron-impact rotationally elastic total cross sections for methanol over an extensive range of impact energy (0.1 – 2000 eV)

Methanol ice co-desorption as a mechanism to explain cold methanol in the gas-phase

Production of complex organic molecules:H-atom addition versus UV irradiation

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