50 research outputs found
Accumulation of three-body resonances above two-body thresholds
We calculate resonances in three-body systems with attractive Coulomb
potentials by solving the homogeneous Faddeev-Merkuriev integral equations for
complex energies. The equations are solved by using the Coulomb-Sturmian
separable expansion approach. This approach provides an exact treatment of the
threshold behavior of the three-body Coulombic systems. We considered the
negative positronium ion and, besides locating all the previously know -wave
resonances, we found a whole bunch of new resonances accumulated just slightly
above the two-body thresholds. The way they accumulate indicates that probably
there are infinitely many resonances just above the two-body thresholds, and
this might be a general property of three-body systems with attractive Coulomb
potentials.Comment: 4 pages, 3 figure
Dissociative recombination and rotational transitions of D in collisions with slow electrons
Rate coefficients for dissociative recombination and state-to-state
rotational transitions of the D ion induced by collisions with very
low-energy electrons have been reported following our previous studies on
HD and H [9,10]. The same molecular structure data sets,
excitations ( for
to ) and de-excitations ( ,
for to ) were used for collision energies ranging from
meV to eV. Isotopic effects for dissociative recombination and rotational
transitions of the vibrationally relaxed targets are presented.Comment: 7 pages, 7 figures, 4 table
Reactive collisions between electrons and BeH+ above dissociation threshold
Our previous studies of dissociative recombination, and vibrational
excitation/de-excitation of the BeH ion, based on the multichannel quantum
defect theory, are extended to collision energies above the dissociation
threshold, taking into account the vibrational continua of the BeH ion and,
consequently, its dissociative excitation. We have also significantly increased
the number of dissociative states of , and
symmetry included in our cross section calculations, generating the most
excited-ones by using appropriate scaling laws. Our results are suitable for
modeling the kinetics of BeH+ in edge fusion plasmas for collision energies up
to 12 eV.Comment: 9 pages, 9 figures
Dissociative recombination of NH: A revisited study
Dissociative recombination of NH is explored in a two-step
theoretical study. In a first step, a diatomic (1D) rough model with frozen NN
bond and frozen angles is adopted, in the framework of the multichannel quantum
defect theory (MQDT). The importance of the indirect mechanism and of the
bending mode is revealed, in spite of the disagreement between our cross
section and the experimental one. In a second step, we use our recently
elaborated 3D approach based on the normal mode approximation combined with
R-matrix theory and MQDT. This approach results in satisfactory agreement with
storage-ring measurements, significantly better at very low energy than the
former calculations.Comment: 9 pages, 5 figures, 1 tabl
Population of ground and lowest excited states of Sulfur via the dissociative recombination of SH+ in the diffuse interstellar medium
Our previous study on dissociative recombination of ground state SH into
states of SH is extended by taking into account the contribution of
states recently explored by quantum chemistry methods. Multichannel
quantum defect theory is employed for the computation of cross sections and
rate coefficients for dissociative recombination, but also for vibrational
excitation. Furthermore, we produce the atomic yields resulting from
recombination, quantifying the generation of sulfur atoms in their ground
(\mbox{P}) and lowest excited (\mbox{D}) states respectively.Comment: 9 pages, 8 figures, 3 table