RESON—A program for the detection and fitting of Breit-Wigner resonances

Tennyson, Jonathan; Noble, C. J.

doi:10.1016/0010-4655(84)90147-4

Cited by 231 publications

(164 citation statements)

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“…The R-matrix calculations were performed on a grid of fixed internuclear distances. The position and width of the resonant state were then calculated by fitting the corresponding eigenphases sum with a Breit-Wigner function [26].…”

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confidence: 99%

Calculated low-energy electron-impact vibrational excitation cross sections for CO₂molecule

Laporta

Tennyson

Celiberto

2016

Plasma Sources Sci. Technol.

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Vibrational-excitation cross sections of ground electronic state of carbon dioxide molecule by electron-impact through the CO − 2 ( 2 Π u ) shape resonance is considered in the separation of the normal modes approximation. Resonance curves and widths are computed for each vibrational mode. The calculations assume decoupling between normal modes and employ the local complex potential model for the treatment of the nuclear dynamics, usually adopted for the electron-scattering involving diatomic molecules. Results are presented for excitation up to 10 vibrational levels in each mode and comparison with data present in the literature is discussed.One of the technological problems, connected with strategies for reduction of the global warming coming from the greenhouse effect produced by carbon dioxide, is represented by the capture at source and storage of the CO 2 gas, mainly based on the plasmolysis process leading to the splitting of CO 2 into CO molecules and atomic or molecular oxygen [1,2]. The efficiency of the dissociation processes is strongly determined by the vibrational activation of the molecule. Models of CO 2 plasmas, aimed to optimize and clarify this chemical conversion, have recently been constructed [3][4][5][6][7]. The main limitation of these models is the lack of information on electron-impact cross sections or rate coefficients for collisions inducing vibrational transitions in CO 2 molecules; as result modellers usually resort to estimated rates or approximate scaling-laws [6].In order to fill this void, in this Letter we present a preliminary data set of electronimpact cross sections for vibrational excitation of ground electronic state of carbon dioxide molecule useful in plasma kinetic modeling. The cross sections show two distinctive features observed experimentally: a 2 Π u shape resonance around 3.8 eV [8][9][10] and, at energies below 2 eV, an enhancement due to the presence of the 2 Σ + g symmetry virtual state [11][12][13]. Both phenomena are explained in terms of a temporary CO − 2 system. For a general review on this topics see Itikawa paper [14] and references therein.We present here the cross sections for the following process:which occurs through the formation of the shape resonance generated by the electronic state 2 Π u of the CO − 2 ion. CO 2 in its ground electronic state, X 1 Σ + g , is a linear molecule with C-O equilibrium distance R eq = 2.19 a 0 characterized by three normal modes of vibration, denoted in the following by v = (ν 1 , ν 2 , ν 3 ) and referred to, respectively, as the symmetric stretching, bending mode (doubly degenerate) and asymmetric stretching. * vincenzo

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confidence: 99%

Calculated low-energy electron-impact vibrational excitation cross sections for CO₂molecule

Laporta

Tennyson

Celiberto

2016

Plasma Sources Sci. Technol.

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“…However, this method struggles to fit closely-spaced and overlapping resonances or ones near to a threshold. The fitting of eigenphase sum to the Breit-Wigner form is automatically done by the module RESON [49] in the UKRmol codes [50].…”

Section: Theorymentioning

confidence: 99%

Higher lying resonances in low-energy electron scattering with carbon monoxide*

Dora

Tennyson

Chakrabarti³

2016

Eur. Phys. J. D

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Abstract. R-matrix calculations on electron collisions with CO are reported whose aim is to identify any higher-lying resonances above the well-reported and lowest 2 Π resonance at about 1.6 eV. Extensive tests with respect to basis sets, target models and scattering models are performed. The final results are reported for the larger cc-pVTZ basis set using a 50 state close-coupling (CC) calculation. The BreitWigner eigenphase sum and the time-delay methods are used to detect and fit any resonances. Both these methods find a very narrow 2 Σ + symmetry Feshbach-type resonance very close to the target excitation threshold of the b 3 Σ + state which lies at 12.9 eV in the calculations. This resonance is seen in the CC calculation using cc-pVTZ basis set while a CC calculation using the cc-pVDZ basis set does not produce this feature. The electronic structure of CO − is analysed in the asymptotic region; 45 molecular states are found to correlate with states dissociating to an anion and an atom. Electronic structure calculations are used to study the behaviour of these states at large internuclear separation. Quantitative results for the total, elastic and electronic excitation cross sections are also presented. The significance of these results for models of the observed dissociative electron attachment of CO in the 10 eV region is discussed.

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“…As more polarization is included, this resonant state moves to lower energies. An automated fit to the eigenphase sums using the Breit-Wigner formula [69] gives the final resonance positions(width) for the conformer I at the 2.7(0.3) eV and 9.8(2.5) eV. The resonance positions(width) for the conformer M are 3.4(0.6) eV and 8.6(1.8) eV.…”

Section: Calculation Detailsmentioning

confidence: 99%

Low-energy electron collisions with the alanine molecule

2014

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Abstract.A theoretical study on elastic electron collisions with two conformers of amino acid alanine (CH3CH(NH2)COOH) is reported. Differential and integral cross sections are computed for collision energies in the 1-10 eV range. The UK molecular R-matrix codes are used to compute scattering amplitudes within the static exchange plus polarization (SEP) approximation. Both alanine conformers have large permanent dipole moment so to calculate cross sections the Born closure procedure is included to take into account long-range interactions. Comparisons of calculated differential cross sections with available data for glycine are made and display certain similarities. Two shape resonances are detected for each conformer: a narrow one located at 2.7 eV and 3.5 eV which is probably associated with the unoccupied π * orbital of the carboxyl group, and a broader resonance at 8.6 eV and 9.8 eV.

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RESON—A program for the detection and fitting of Breit-Wigner resonances

Cited by 231 publications

References 3 publications

Calculated low-energy electron-impact vibrational excitation cross sections for CO₂molecule

Calculated low-energy electron-impact vibrational excitation cross sections for CO₂molecule

Higher lying resonances in low-energy electron scattering with carbon monoxide*

Low-energy electron collisions with the alanine molecule

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RESON—A program for the detection and fitting of Breit-Wigner resonances

Cited by 231 publications

References 3 publications

Calculated low-energy electron-impact vibrational excitation cross sections for CO2molecule

Calculated low-energy electron-impact vibrational excitation cross sections for CO2molecule

Higher lying resonances in low-energy electron scattering with carbon monoxide*

Low-energy electron collisions with the alanine molecule

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Product

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Calculated low-energy electron-impact vibrational excitation cross sections for CO₂molecule

Calculated low-energy electron-impact vibrational excitation cross sections for CO₂molecule