Abstract EN:

Small open quantum systems, whose properties are profoundly affected by the environment of continuum states, are intensely studied in various fields of Physics: nuclear physics, atomic and molecular physics, quantum optics, etc. These different many-body systems, in spite of their specific features, have generic properties which are common to all weakly bound or unbound systems close to the threshold. Coupling to the continuum is essential to describe the low-energy nuclear reactions of astrophysical interest, the formation of halo states in nuclei, atomic clusters and dipolar anions, or the near-threshold two neutron and alpha particle correlations (clustering). Recently, the open quantum system extension of the nuclear shell model, the Gamow shell model (GSM), based on the Berggren ensemble, has been applied successfully for the description of resonant states spectra in atomic nuclei. The coupled-channel formulation of the GSM (GSM-CC) allows to describe various low-energy nuclear reactions. In this work, the GSM-CC is formulated and applied for the description of proton/neutron radiative capture reactions of astrophysical interest, such as: 17F ( p , gamma ) 18Ne, 7Be ( p , gamma ) 8B and 7Li ( n , gamma ) 8Li. Moreover, for the first time, the GSM has been applied in atomic physics for the description of spectra of dipolar anions. Systematic investigation of the hydrogen cyanide dipolar anion (HCN-) allowed to identify the collective bands of states both in the strong coupling regime, for weakly bound halo states, and in the weak coupling regime above the dissociation threshold. In the strong coupling regime, K_J = 0 anion a rotational band has been found. Above the threshold, K_J quantum number is not conserved. Resonances in this regime form rotational bands according to the angular momentum of the rotating molecule, whereas the bandhead energies and the lifetimes depend predominantly on the external electron wave function.