Calculations of Effusive-Flow Patterns. II. Scattering Chambers with Semi-Infinite Slits

Nelson, R. N.; Colgate, S. O.

doi:10.1103/physreva.8.3045

Cited by 48 publications

(20 citation statements)

References 8 publications

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“…Another inevitable error comes from the effusion of target molecules through orifices of the scattering cell leading to inhomogeneity of target density in the reaction volume and to elongation of the effective path over which the scattering events take place. 10 We also noticed that the increasing contamination of the electron optics elements with the target molecules causes a gradual drift in the energy scale during the experiment. The energy drift, by about 0.1 eV, is especially troublesome at low electron-impact energies where the TCS may change steeply with the energy and/or has resonant-like structures.…”

Section: Methodsmentioning

confidence: 84%

Electron collisions with methyl-substituted ethylenes: Cross section measurements and calculations for 2-methyl–2-butene and 2,3-dimethyl–2-butene

Szmytkowski

Stefanowska

Zawadzki

et al. 2015

The Journal of Chemical Physics

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We report electron-scattering cross sections determined for 2-methyl-2-butene [(H3C)HC = C(CH3)2] and 2,3-dimethyl-2-butene [(H3C)2C = C(CH3)2] molecules. Absolute grand-total cross sections (TCSs) were measured for incident electron energies in the 0.5-300 eV range, using a linear electron-transmission technique. The experimental TCS energy dependences for the both targets appear to be very similar with respect to the shape. In each TCS curve, three features are discernible: the resonant-like structure located around 2.6-2.7 eV, the broad distinct enhancement peaking near 8.5 eV, and a weak hump in the vicinity of 24 eV. Theoretical integral elastic (ECS) and ionization (ICS) cross sections were computed up to 3 keV by means of the additivity rule (AR) approximation and the binary-encounter-Bethe method, respectively. Their sums, (ECS+ICS), are in a reasonable agreement with the respective measured TCSs. To examine the effect of methylation of hydrogen sides in the ethylene [H2C = CH2] molecule on the TCS, we compared the TCS energy curves for the sequence of methylated ethylenes: propene [H2C = CH(CH3)], 2-methylpropene [H2C = C(CH3)2], 2-methyl-2-butene [(H3C)HC = C(CH3)2], and 2,3-dimethyl-2-butene [(H3C)2C = C(CH3)2], measured in the same laboratory. Moreover, the isomeric effect is also discussed for the C5H10 and C6H12 compounds.

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Section: Methodsmentioning

confidence: 84%

Electron collisions with methyl-substituted ethylenes: Cross section measurements and calculations for 2-methyl–2-butene and 2,3-dimethyl–2-butene

Szmytkowski

Stefanowska

Zawadzki

et al. 2015

The Journal of Chemical Physics

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“…Taking into account theoretical elastic differential cross sections [19,20,26], we found that the measured TCS can be lowered by 4-5% around 3 eV, about 2-3% within tor nL in the BBL formula we followed the method adopted from Ref. [33] to the present experimental conditions. The calculations show that both aforementioned effects nearly compensate and the estimated uncertainty of nL is about 2-3%, taking also into account the uncertainty in the pressure measurements.…”

Section: B Uncertainty Analysismentioning

confidence: 99%

Cross sections for electron collision with pyridine [C₅H₅N] molecule

et al. 2018

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The absolute grand -total cross section (TCS) for electron scattering from pyridine, C 5 H 5 N, molecules has been measured at impact energies from 0.6 to 300 eV in the linear electrontransmission experiment. The obtained TCS energy dependence appears to be typical for targets of high electric dipole moment; the cross section generally decreases with rising energy, except for the 3-20 eV range, where a broad enhancement peaked near 8.5 eV is clearly visible. Below 10 eV, some weak structures which can be attributed to resonant scattering processes are also discernible.The present TCS energy dependence is compared with TCS experimental data obtained recently for energies above 13 eV by Traoré Dubuis et al. [26]. The TCS for pyridine has been confronted with TCS for benzene to search how the replacement of the CH group in the benzene ring with the nitrogen atom influences the electron scattering process. In addition, for pyridine and its halogenated derivatives: 2-chloropyridine [2-C 5 H 4 ClN] and 2-bromopyridine [2-C 5 H 4 BrN], integral elastic (ECS) and ionization (ICS) cross sections have been calculated at intermediate and high electron-impact energies within semiempirical approaches. For pyridine the sum of ECS and ICS is in reasonable agreement with the measured TCS above 40 eV.

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“…Following the electron path-length calculations [38], we have estimated that the denominator pL in the BBL formula, taken as the product of the pressure, p, measured in the center of the cell and the geometrical distance (L = 30.5 mm) between entrance and exit cell apertures, may be erroneous to within 2%.…”

Section: Measurementsmentioning

confidence: 99%

Electron-scattering cross sections for selected alkyne molecules: Measurements and calculations

et al. 2014

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We report cross-section results from experimental and theoretical studies on electron collisions with 1-butyne (HC≡C-CH 2 CH 3 ) and acetylene (HC≡CH) molecules and from computations for a propyne (HC≡C-CH 3 ) molecule. Absolute grand -total electron-scattering cross sections (TCSs) were measured at impact energies ranging from about 0.5 to 300 eV using the linear electron-transmission method. The TCS energy curve for 1-butyne has a very broad enhancement on which some distinct features are superimposed, namely a resonant-like maximum (located near 3.2 eV), a broad hump (centered around 7.5 eV), and a shoulder (spanned between 12 and 26 eV). The shape of our experimental TCS curve for acetylene closely resembles that reported earlier, while its magnitude is usually larger. As no previous calculations for electron collisions with 1-butyne and propyne are disclosed in the literature, we computed the elastic (ECS) and ionization (ICS) cross sections for these molecules. Similar calculations were also performed for acetylene molecules. The additivity rule was employed to calculate the ECSs from 50 to 3000 eV, while the binary-encounter-Bethe approach was used for computation of the ICSs, from the threshold up to 3000 eV. The sum (ECS + ICS) of these two computed cross sections reasonably reproduces the TCS measurements above 50 eV. Furthermore, the experimental TCS curves, obtained in our laboratory, for a series of acetylenic compounds-acetylene (HC≡CH), propyne (HC≡C-CH 3 ), and 1-butyne (HC≡C-CH 2 CH 3 )-are compared to study the substitutional effect. Finally, the influence of the structural differences on the electron-scattering TCS for isomers of the C 4 H 6 molecule (1-butyne, 2-butyne, and 1,3-butadiene) is indicated and discussed.

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Calculations of Effusive-Flow Patterns. II. Scattering Chambers with Semi-Infinite Slits

Cited by 48 publications

References 8 publications

Electron collisions with methyl-substituted ethylenes: Cross section measurements and calculations for 2-methyl–2-butene and 2,3-dimethyl–2-butene

Electron collisions with methyl-substituted ethylenes: Cross section measurements and calculations for 2-methyl–2-butene and 2,3-dimethyl–2-butene

Cross sections for electron collision with pyridine [C₅H₅N] molecule

Electron-scattering cross sections for selected alkyne molecules: Measurements and calculations

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Calculations of Effusive-Flow Patterns. II. Scattering Chambers with Semi-Infinite Slits

Cited by 48 publications

References 8 publications

Electron collisions with methyl-substituted ethylenes: Cross section measurements and calculations for 2-methyl–2-butene and 2,3-dimethyl–2-butene

Electron collisions with methyl-substituted ethylenes: Cross section measurements and calculations for 2-methyl–2-butene and 2,3-dimethyl–2-butene

Cross sections for electron collision with pyridine [C5H5N] molecule

Electron-scattering cross sections for selected alkyne molecules: Measurements and calculations

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Cross sections for electron collision with pyridine [C₅H₅N] molecule