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Calculations are performed for electron collision with the methylene molecular ion C H 2 + in its bent equilibrium geometry, with the goal of obtaining cross sections for electron impact excitation and dissociation. The polyatomic version of the UK molecular R -matrix codes was used to perform an initial configuration-interaction calculation on the doublet and quartet states of the C H 2 + ion. Subsequently, scattering calculations are performed to obtain electron impact electronic excitation and dissociation cross sections and, additionally, the bound states of the CH2 molecule and Feshbach resonances in the e - C H 2 + system. [ABSTRACT FROM AUTHOR]

Cross section data for electron impact electronic excitation of electronically excited states of H2 are computed using fixed-nuclear R-matrix calculations. Specifically, there is a focus on transitions from the quasi-metastable excited states and. Data are compared with known theoretical data where available. Our calculations suggest that the published cross sections are generally too large in the low energy (<20 eV) collision region. The effect of shifting the electronic excitation thresholds to those given by essentially exact calculations is tested. [ABSTRACT FROM AUTHOR]

We present benchmark integrated and differential cross-sections for electron collisions with H2 using two different theoretical approaches, namely, the R-matrix and molecular convergent close-coupling. This is similar to comparative studies conducted on electron–atom collisions for H, He and Mg. Electron impact excitation to the , , , c3Πu, , C1Πu, , , and d3Πu excited electronic states are considered. Calculations are presented in both the fixed nuclei and adiabatic nuclei approximations, where the latter is shown only for the state. Good agreement is found for all transitions presented. Where available, we compare with existing experimental and recommended data. [ABSTRACT FROM AUTHOR]

Beryllium is being adopted for plasma facing walls in fusion reactors. This has led to the observation of emissions from the A 2Π state of beryllium hydride. Use of these emissions to monitor Be erosion requires electron impact excitation rates. Cross sections for electron impact vibrational excitation within the X 2Σ+ state and vibrationally resolved electronic excitation to the A 2Π state are reported for BeH, BeD and BeT. Electron collisions are studied at a range of internuclear separations using the UK molecular R-matrix (UKRmol+) codes. Electronic excitation is studied both within the Franck–Condon approximation and by explicit averaging of the T-matrix elements. It is found that (a) inclusion of the effect of higher partial waves using the Born approximation leads to significant increases in the cross sections and (b) the Franck–Condon approximation underestimates the importance of collisions for which the vibrational state changes during electronic excitation. [ABSTRACT FROM AUTHOR]

Electron collisions with CHOH are studied up to impact energies of 10 eV using several theoretical models. Calculated differential cross sections suggest that the extrapolation to low angles used to extend experimental data and hence give integral cross sections significantly underestimates the large, dipole-driven forward scattering cross section. An improved set of values for the rotationally-unresolved elastic cross section is proposed; the corresponding rotationally resolved cross sections are also presented. Static exchange plus polarisation calculations find a very broad shape resonance in each of the A′ and A′′ symmetries in the 7 eV collision region however no resonance at lower energies, in qualitative agreement with the interpretation of some but not all dissociative electron attachment measurements. [ABSTRACT FROM AUTHOR]

We describe the UK computational implementation of the R-matrix method for the treatment of electron and positron scattering from molecules. Recent developments in the UKRmol suite are detailed together with the collision processes it is enabling us to treat. [ABSTRACT FROM AUTHOR]

We present the latest developments of the R-matrix method as applied to electron-molecule collisions. A variety of calculations for H2O are presented including the study of rotational excitation and preliminary data for dissociative electron attachment. Results for the application of the recently developed molecular R-matrix with pseudostates (MRMPS) method to neutral and cationic targets are also included. This method is currently being applied to the study of collisions with anionic targets. [ABSTRACT FROM AUTHOR]

ABSTRACT New coupled-state R-matrix calculations are performed at energies up to 1 eV to give rotational excitation and de-excitation cross-sections for electron collisions with CH[sup +]. Rotational excitations with Δ j up to 7 are considered. Transitions with Δ j up to 6 are found to have appreciable cross-sections, those with Δ j = 2 being comparable to (indeed slightly larger than) those with Δ j = 1, the only ones considered previously. Rates for electron temperatures up to 15 000 K and critical electron densities are given. A model of CH[sup +] rotational populations shows them to be relatively insensitive to electron temperatures in the range 800–2000 K, but to depend strongly upon electron density. The models predict a significant population in rotational states with j > 1 even at low electron densities; at higher densities the possibility exists that electron collisions alone might explain the recently observed populations in the planetary nebula NGC 7027. [ABSTRACT FROM AUTHOR]

We provide cross sections and Maxwell rate coefficients for reactive collisions of slow electrons with BeH + ions on all the eighteen vibrational levels ( X 1 Σ + , v i + = 0 , 1 , 2 , … , 17 ) using a Multichannel Quantum Defect Theory (MQDT)—type approach. These data on dissociative recombination, vibrational excitation and vibrational de-excitation are relevant for magnetic confinement fusion edge plasma modeling and spectroscopy, in devices with beryllium based main chamber materials, such as the International Thermonuclear Experimental Reactor (ITER) and the Joint European Torus (JET). Our results are presented in graphical form and as fitted analytical functions, the parameters of which are organized in tables. [ABSTRACT FROM AUTHOR]

Abstract: Dissociative electron attachment cross sections (DEA) on vibrationally excited H2 molecule taking place via the Rydberg-excited resonant state are studied using the local complex potential (LCP) model for resonant collisions. The cross sections are calculated for all initial vibrational levels (v i =0–14) of the neutral molecule. In contrast to the previously noted dramatic increase in the DEA cross sections with increasing v i , when the process proceeds via the X shape resonance of H2, for the Rydberg resonance the cross sections increase only gradually up to v i =3 and then decrease. Moreover, the cross sections for v i ⩾6 exhibit pronounced oscillatory structures. A discussion of the origin of the observed behavior of calculated cross sections is given. The DEA rate coefficients for all v i levels are also calculated in the 0.5–1000eV temperature range. [Copyright &y& Elsevier]