Abstract. We present a detailed computational analysis for the interaction between the vibrating/rotating molecular ions H + 2 , HD + , D + 2 colliding with He atoms employed as buffer gas within ion trap experiments. The production and preparation of these molecular ions from their neutrals usually generate rovibrationally excited species which will therefore require internal energy cooling down to their ground vibrational levels for further experimental handling. In this work we describe the calculation of the full 3D interaction potentials and of the ionic vibrational levels needed to obtain the vibrational coupling potential matrix elements which are needed in the multichannel treatment of the rovibrationally inelastic collision dynamics. The general features of such coupling potential terms are discussed for their employment within a quantum dynamical modeling of the relaxation processes, as well as in connection with their dependence on the initial and final vibrational levels which are directly coupled by the present potentials. As a preliminary test of the potential effects on scattering observables, we perform calculations between H + 2 and He atoms at the energies of an ion-trap by using either the rigid rotor (RR) approximation or the more accurate vibrationally averaged (VA) description for the v = 0 state of the target. Both schemes are described in detail in the present paper and the differences found in the scattering results are also analysed and discussed. We further present and briefly discuss some examples of state-to-state rovibrationally inelastic cross sections, involving the two lowest vibrational levels of the H + 2 molecular target ion, as obtained from our time-independent multichannel quantum scattering code.

This paper deals with the possible formation of two molecular anions often considered likely components in the physical environments of the Interstellar Medium ( ISM) : C 2 H − and NCO − . They are both discussed here by computationally following the radiative association (RA) mechanism starting from C − 2 , H, NC − and O as partners. The corresponding RA total cross sections produced by the calculations are in turn employed to generate the overall association rates over the relevant range of temperatures. The latter are found to be in line with other molecular ions formed by RA but not large enough to uniquivocally suggest this path as the main route to the anions formation in the ISM. Other possible paths of formation are also analysed and discussed.The presence of resonant structures during the association dynamics for both systems is found by the calculations and their consequences are discussed in some detail in the present study.