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

Vinodkumar, Minaxi; Limbachiya, Chetan; Barot, Avani; Mason, Nigel J.

doi:10.1103/physreva.87.012702

Cited by 32 publications

(23 citation statements)

References 53 publications

(112 reference statements)

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“…At lower energy, short-range forces can become important, and these effects were found to reduce the low-energy cross-sections by up to a factor of ∼1.5. In the case of methanol, the Born treatment probably overestimates the rotational cross-sections by a factor of 2-3, as suggested by the measurements of the total elastic cross-section (see Vinodkumar et al 2013, and references therein). In the Born approximation, cross-sections are proportional to line strengths and the square of the dipole and therefore strictly obey the dipolar selection rule.…”

Section: Ch 3 Ohmentioning

confidence: 98%

The IRAM-30 m line survey of the Horsehead PDR

Guzmán

Goicoechea

Pety

et al. 2013

A&A

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Context. Theoretical models and laboratory experiments show that CH 3 OH is efficiently formed on cold grain surfaces through the successive hydrogenation of CO, forming HCO and H 2 CO as intermediate species.In cold cores and low UV-field illumination photodissociation regions (PDRs) the ices can be released into the gas-phase through nonthermal processes such as photodesorption, which considerably increases their gas-phase abundances. Aims. We investigate the dominant formation mechanism of H 2 CO and CH 3 OH in the Horsehead PDR and its associated dense core.Methods. We performed deep integrations of several H 2 CO and CH 3 OH lines at two positions in the Horsehead, namely the PDR and dense core, with the IRAM-30 m telescope. In addition, we observed one H 2 CO higher-frequency line with the CSO telescope at both positions. We determined the H 2 CO and CH 3 OH column densities and abundances from the single-dish observations complemented with IRAM-PdBI high-angular resolution maps (6 ) of both species. We compared the observed abundances with PDR models including either pure gas-phase chemistry or both gas-phase and grain surface chemistry.Results. We derived CH 3 OH abundances relative to total number of hydrogen atoms of ∼1.2 × 10 −10 and ∼2.3 × 10 −10 in the PDR and dense-core positions, respectively. These abundances are similar to the inferred H 2 CO abundance in both positions (∼2 × 10 −10 ). We find an abundance ratio H 2 CO/CH 3 OH of ∼2 in the PDR and ∼1 in the dense core. Pure gas-phase models cannot reproduce the observed abundances of either H 2 CO or CH 3 OH at the PDR position. The two species are therefore formed on the surface of dust grains and are subsequently photodesorbed into the gas-phase at this position. At the dense core, on the other hand, photodesorption of ices is needed to explain the observed abundance of CH 3 OH, while a pure gas-phase model can reproduce the observed H 2 CO abundance. The high-resolution observations show that CH 3 OH is depleted onto grains at the dense core. CH 3 OH is thus present in an envelope around this position, while H 2 CO is present in both the envelope and the dense core itself. Conclusions. Photodesorption is an efficient mechanism to release complex molecules in low-FUV-illuminated PDRs, where thermal desorption of ice mantles is ineffective.

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Section: Ch 3 Ohmentioning

confidence: 98%

The IRAM-30 m line survey of the Horsehead PDR

Guzmán

Goicoechea

Pety

et al. 2013

A&A

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“…The BEB method uses an analytic formula that requires the incident particle energy, the target particle's binding energy and the target particle's kinetic energy to generate direct ionisation cross section curves, which are reliable in intensity (±20%) and shape from the ionisation threshold to a few keV in the nonrelativistic version of BEB [35,36]. We have computed Q ion data for the present targets using the BEB method by the QuanteMol-N package [26] to provide a comparison for the ionisation cross sections calculated using the CSP-ic method [31].…”

Section: Complex Scattering Potential-ionisationmentioning

confidence: 99%

“…These charge densities are then added. The molecular charge density, ρ(r), so obtained is renormalised to incorporate the covalent bonding [26] and used to generate the potentials mentioned in Equation (1). The optical potential thus created is used in the Schrödinger equation which is solved numerically using partial wave analysis to obtain complex phase shifts which, in turn, are used to compute various total cross sections [27].…”

Section: Spherical Complex Optical Potential (Scop)mentioning

confidence: 99%

Electron-impact total cross sections for inelastic processes for furan, tetrahydrofuran and 2,5-dimethylfuran

Limbachiya

Vinodkumar²,

Swadia

et al. 2014

Molecular Physics

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We report total inelastic, total ionisation and summed total excitation cross sections for electron scattering on furan, tetrahydrofuran (THF) and 2,5-dimethylfuran at energies between the ionisation threshold and 5 keV. We have employed the spherical complex optical potential formalism (SCOP) to calculate the total inelastic cross sections (Q inel ) and have used complex scattering potential-ionisation contribution (CSP-ic) method to derive total ionisation cross sections (Q ion ) and summed total excitation cross sections ( Q exc ) from the calculated Q inel . We have also computed Q ion for these molecules using binary-encounter-Bethe (BEB) approach. We have compared our total cross sections (TCS) with available experimental as well as previous theoretical results and have found good agreement. The results are presented graphically as well as numerically.

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“…Methanol is the smallest alcohol and has therefore been the most studied as it can be considered as a prototype for larger alcohols. Experimental and theoretical investigations include total [7][8][9][10][11][12][13][14] and elastic differential cross sections [13,[15][16][17], from which integral cross sections and momentum transfer cross sections can also be derived. Most recently, there has been a study of the electronic excitation of methanol by electron impact [18] which is important as the excited electronic states may provide a pathway to neutral dissociation.…”

Section: Introductionmentioning

confidence: 99%

Electron impact ionisation and fragmentation of methanol and ethanol

Nixon

Pires

Neves

et al. 2016

International Journal of Mass Spectrometry

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Electron impact ionisation and dissociative ionisation of the two smallest primary alcohols have been investigated. A quadrupole mass spectrometer was used, with an internal ionising electron source resulting in an energy resolution of ~ 0.8 eV. The partial ionisation cross sections (PICS) for a number of individual cations have been measured for energies between 10 - 100 eV. The present data compares well with previous results for methanol. Surprisingly, however, this study is the first to report individual PICS for ethanol. The sum of the present PICS for both methanol and ethanol is also compared to the total ionisation cross sections reported in the literature and are found to be in good accord. Additionally, appearance energies have been derived by fitting the Wannier equation to data measured within ~ 2 eV of the cation formation threshold. However, the low energy resolution limits the precision with which these values are able to be determined. This study also establishes the validity of the data collected using the apparatus at Universidade Federal de Juiz de Fora (UFJF) and so provides a solid foundation for further studies of larger alcohols

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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)

Cited by 32 publications

References 53 publications

The IRAM-30 m line survey of the Horsehead PDR

The IRAM-30 m line survey of the Horsehead PDR

Electron-impact total cross sections for inelastic processes for furan, tetrahydrofuran and 2,5-dimethylfuran

Electron impact ionisation and fragmentation of methanol and ethanol

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