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 $S$-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 D2+_2^+ in collisions with slow electrons

Rate coefficients for dissociative recombination and state-to-state rotational transitions of the D$_{2}^{+}$ ion induced by collisions with very low-energy electrons have been reported following our previous studies on HD$^{+}$ and H$_{2}^{+}$ [9,10]. The same molecular structure data sets, excitations ($N_{i}^{+} \rightarrow$ $N_{f}^{+}=N_{i}^{+}+2$ for $N_{i}^{+}=0$ to $10$) and de-excitations ($N_{i}^{+}$ $\rightarrow$ $N_{f}^{+}=N_{i}^{+}-2$, for $N_{i}^{+}=2$ to $10$) were used for collision energies ranging from $0.01$ meV to $0.3$ eV. Isotopic effects for dissociative recombination and rotational transitions of the vibrationally relaxed targets are presented.Comment: 7 pages, 7 figures, 4 table

Dissociative recombination of N2_2H+^+: A revisited study

Dissociative recombination of N$_2$H$^+$ 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 $^2\Pi$ states of SH is extended by taking into account the contribution of $^4\Pi$ 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{$^3$P}) and lowest excited (\mbox{$^1$D}) states respectively.Comment: 9 pages, 8 figures, 3 table