Dissociative electron attachment and vibrational excitation of CF3Cl\mathbf{CF_3Cl}: Effect of two vibrational modes revisited

We present a study of dissociative electron attachment and vibrational excitation processes in electron collisions with the CF$_3$Cl molecule. The calculations are based on the two-dimensional nuclear dynamics including the C-Cl symmetric stretch coordinate and the CF$_3$ symmetric deformation (umbrella) coordinate. The complex potential energy surfaces are calculated using the ab initio R-matrix method. The results for dissociative attachment and vibrational excitation of the umbrella mode agree quite well with experiment while the cross section for excitation of the C-Cl symmetric stretch vibrations is about a factor of three low as compared to experimental data.Comment: 24 pages, 7 figures, submitted to Physical Review

Role of electronic correlations in photoionization of NO2 in the vicinity of the 2A1/2B2 conical intersection

We present the first ab initio multi-channel photoionization calculations for NO2 in the vicinity of the 2A1/2B2 conical intersection, for a range of nuclear geometries, using our newly developed set of tools based on the ab initio multichannel R-matrix method. Electronic correlation is included in both the neutral and the scattering states of the molecule via configuration interaction. Configuration mixing is especially important around conical intersections and avoided crossings, both pertinent for NO2, and manifests itself via significant variations in photoelectron angular distributions. The method allows for a balanced and accurate description of the photoionization/photorecombination for a number of different ionic channels in a wide range of photoelectron energies up to 100 eV. Proper account of electron correlations is crucial for interpreting time-resolved signals in photoelectron spectroscopy and high harmonic generation (HHG) from polyatomic molecules

Probing the nonlocal approximation to resonant collisions ofelectrons with diatomic molecules

A numerically solvable two-dimensional model introduced bythe authors [Phys. Rev. A 73, 032721 (2006)]is used to investigate thevalidity of the nonlocal approximation to the dynamics of resonantcollisions of electrons with diatomic molecules. The nonlocalapproximation to this model is derived in detail, all underlyingassumptions are specified and explicit expressions for the resonant andnon-resonant (background) T matrix for the studied processes are given.Different choices of the so-called discrete state, which fully determinesthe nonlocal approximation, are discussedand it is shown that a physicalchoice of this state can in general give poorer results than otherchoices that minimize the non-adiabatic effects and/or the backgroundterms of the T matrix. The background contributions to the crosssections, which are usually not considered in the resonant theory ofelectron-molecule collisions, can be significant not only for elasticscattering but also for the inelastic process of vibrationalexcitation

UKRmol-scripts: a Perl-based system for the automated operation of the photoionization and electron/positron scattering suite UKRmol+

UKRmol-scripts is a set of Perl scripts to automatically run the UKRmol+ codes, a complex software suite based on the R-matrix method to calculate fixed-nuclei photoionization and electron- and positron-scattering for polyatomic molecules. Starting with several basic parameters, the scripts operatively produce all necessary input files and run all codes for electronic structure and scattering calculations as well as gather the more frequently required outputs. The scripts provide a simple way to run such calculations for many molecular geometries concurrently and collect the resulting data for easier post-processing and visualization. We describe the structure of the scripts and the input parameters as well as provide examples for photoionization and electron and positron collisions with molecules. The codes are freely available from Zenodo

Cross section and rate constants of resonant low-energy electron-molecule collisions.

Available from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi

Lowest autodetachment state of the water anion

The potential energy surface of the ground state of the water anion H2O− is carefully mapped using multireference CI calculations for a large range of molecular geometries. Particular attention is paid to a consistent description of both the O−+H2 and OH−+H asymptotes and to a relative position of the anion energy to the ground state energy of the neutral molecule. The autodetachment region, where the anion state crosses to the electronic continuum is identified. The local minimum in the direction of the O− + H2 channel previously reported by Werner et al. [J. Chem. Phys. 87, 2913 (1987)] is found to be slighly off the linear geometry and is separated by a saddle from the autodetachment region. The autodetachment region is directly accessible from the OH−+H asymptote. For the molecular geometries in the autodetachment region and in its vicinity we also performed fixed-nuclei electron-molecule scattering calculations using the R-matrix method. Tuning of consistency of a description of the correlation energy in both the multireference CI and R-matrix calculations is discussed. Two models of the correlation energy within the R-matrix method that are consistent with the quantum chemistry calculations are found. Both models yield scattering quantities in a close agreement. The results of this work will allow a consistent formulation of the nonlocal resonance model of the water anion in a future publication