Calculated rotational and vibrational excitation rates for electron—HeH+ collisions

Rabadán, I.; Sarpal, B K; Tennyson, Jonathan

doi:10.1046/j.1365-8711.1998.01741.x

Cited by 28 publications

(35 citation statements)

References 14 publications

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“…(12). The required value of the cross section constant σ 0 (amounting to ∼10 4Å2 ) is not unrealistic [55] and slightly smaller values may in fact be sufficient if transitions other than ∆J = ±1 [54] are considered in addition. Fig.…”

Section: Rotational Excitation and Coolingmentioning

confidence: 98%

“…(3) with v = v ′ ] we parameterize the rotational excitation cross section, inspired by the formulation given by Rabadan et al [54], as…”

Section: Rotational Excitation and Coolingmentioning

confidence: 99%

“…[54]). It must be expected that such reactions play a significant role for other storage ring measurements on DR too.…”

Section: Rotational Excitation and Coolingmentioning

confidence: 99%

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Dissociative recombination and low-energy inelastic electron collisions of the helium dimer ion

et al. 2005

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The dissociative recombination (DR) of 3 He 4 He + has been investigated at the heavy-ion Test Storage Ring (TSR) in Heidelberg by observing neutral products from electron-ion collisions in a merged beams configuration at relative energies from near-zero (thermal electron energy about 10 meV) up to 40 eV. After storage and electron cooling for 35 s, an effective DR rate coefficient at nearzero energy of 3 × 10 −9 cm 3 s −1 is found. The temporal evolution of the neutral product rates and fragment imaging spectra reveals that the populations of vibrational levels in the stored ion beam are non-thermal with fractions of ∼0.1-1% in excited levels up to at least v = 4, having a significant effect on the observed DR signals. With a pump-probe-type technique using DR fragment imaging while switching the properties of the electron beam, the vibrational excitation of the ions is found to originate mostly from ion collisions with the residual gas. Also, the temporal evolution of the DR signals suggests that a strong electron induced rotational cooling occurs in the vibrational ground state, reaching a rotational temperature near or below 300 K. From the absolute rate coefficient and the shape of the fragment imaging spectrum observed under stationary conditions, the DR rate coefficient from the vibrational ground state is determined; converted to a thermal electron gas at 300 K it amounts to (3.3 ± 0.9) × 10 −10 cm 3 s −1 . The corresponding branching ratios from v = 0 to the atomic final states are found to be (3.7 ± 1.2)% for 1s2s 3 S, (37.4 ± 4.0)% for 1s2s 1 S, (58.6 ± 5.2)% for 1s2p 3 P , and (2.9 ± 3.0)% for 1s2p 1 P . A DR rate coefficient in the range of 2 × 10 −7 cm 3 s −1 or above is inferred for vibrational levels v = 3 and higher. As a function of the collision energy, the measured DR rate coefficient displays a structure around 0.2 eV. At higher energies, it has one smooth peak around 7.3 eV and a highly structured appearance at 15-40 eV. The small size of the observed effective DR rate coefficient at near-zero energy indicates that the electron induced rotational cooling is due to inelastic electron-ion collisions and not due to selective depletion of rotational levels by DR.

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Section: Rotational Excitation and Coolingmentioning

confidence: 98%

“…(3) with v = v ′ ] we parameterize the rotational excitation cross section, inspired by the formulation given by Rabadan et al [54], as…”

Section: Rotational Excitation and Coolingmentioning

confidence: 99%

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Dissociative recombination and low-energy inelastic electron collisions of the helium dimer ion

et al. 2005

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“…Vibrational transition v → v labels are shown in each panel. Results of a previous calculation [15] are shown by dashed lines.…”

Section: Rate Coefficients and Cross Sections For Vibrational (De-)exmentioning

confidence: 94%

“…for which cross sections were calculated in a previous study [15] for the transitions between the three lowest vibrational levels v = 0, 1, 2. In that study, an R-matrix approach was employed to determine scattering matrices for fixed geometries.…”

Section: Introductionmentioning

confidence: 99%

Cross Sections and Rate Coefficients for Vibrational Excitation of HeH+ Molecule by Electron Impact

Ayouz

Kokoouline

2016

Atoms

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Abstract:Cross sections and thermally-averaged rate coefficients for vibration (de-)excitation of HeH + by an electron impact are computed using a theoretical approach that combines the multi-channel quantum defect theory and the UK R-matrix code. Fitting formulas with a few numerical parameters are derived for the obtained rate coefficients. The interval of applicability of the formulas is from 40 to 10,000 K.

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Electron–molecule collision calculations using the R-matrix method

2010

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Calculated rotational and vibrational excitation rates for electron—HeH+ collisions

Cited by 28 publications

References 14 publications

Dissociative recombination and low-energy inelastic electron collisions of the helium dimer ion

Dissociative recombination and low-energy inelastic electron collisions of the helium dimer ion

Cross Sections and Rate Coefficients for Vibrational Excitation of HeH+ Molecule by Electron Impact

Electron–molecule collision calculations using the R-matrix method

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