Dissociative recombination ofN2+: Anab initiostudy

Abstract

Cross sections for the dissociative recombination of N + 2 for v + i = 0-3 are computed using multichannel quantum defect theory with molecular data generated using the R-matrix method. The calculation is completely ab initio and includes three electronic cores of the ion. Extensive comparisons are made with previous experimental and theoretical studies. Our cross section is in excellent agreement with experimental results and other theoretical results. Cross sections and isotropic rate coefficients are provided for all computed vibrational levels.

TIMEDELn: A programme for the detection and parametrization of overlapping resonances using the time-delay method

“…Branching ratios are also functions of energy and can vary across the resonance, although in the case of [23] the branching ratios were effectively constant across the narrow resonances (supported by data from the indicative benchmarks and more broadly from the pyrimidine test run in section 4.3). The code provides options to calculate branching ratios across a range of energies within the resonance in the routine BRANCHING RATIOS.…”

“…When resonances are strongly overlapping, the relationship between the time-delay eigenvalues and the branching ratios is not given straightforwardly by (3), as investigated by Shimamura [11]. However, we have found empirically that if the separation leads to clearly defined Lorentzian peaks (with the peak maxima originally in the largest eigenvalue) then the formula gives consistent results away from the avoided crossings (see [23], also data from the current indicative benchmarks and test runs are available from the authors).…”

“…Partial widths for each partial wave of a channel are calculated by multiplying Γ by the β i . The partial width for a specific channel can be found by summing over the partial widths of the partial waves, as was done by Little et al [23]. Having autoionisation widths resolved in this way is necessary for a dissociative recombination cross-section calculation which includes core-excited bound states, see Little et al [23].…”

“…The partial width for a specific channel can be found by summing over the partial widths of the partial waves, as was done by Little et al [23]. Having autoionisation widths resolved in this way is necessary for a dissociative recombination cross-section calculation which includes core-excited bound states, see Little et al [23]. The extraction of branching ratios using (3) is accurate when the resonance is isolated and the peak appears in the largest eigenvalue, as shown by Smith [8].…”

“…The serial version simply calls PTIMEDEL (and any other sub-programs the user may also wish to run) whereas the parallel main code first changes to multiple sub-directories for simultaneous runs as required by the user, splits the    communicator to match these subdirectory calculations, calls PTIMEDEL and finally calls MPI Finalize: again, other sub-program calls may be inserted by the user (expert user-developers may wish to return to the initial directory for other work). This initial parallelization allows controlled task-farming of many 'similar but different' jobs and was originally de-veloped to allow bulk production of resonance data for the N 2 calculations (as in [23,25]) at various fixed internuclear separations in a single job, independently of the hardware and operating system. More generally it can be used for bulk calculations for different molecular geometries, or different irreducible representations, although it is up to the user to make sure the 'similar but different' rule applies, to maintain reasonable load balancing.…”