A single-center method for calculating photodetachment cross section for anions and radiative electron attachment cross section for neutral molecules by microreversibility is presented. It uses the integral equation method to calculate the ejected electron's continuum wave function while the single-electron bound function of the anion is described by the Dyson orbital. It is compared with related theoretical approaches and benchmarked to the experimental photodetachment cross sections of O 2 − , OH − , and CN − . The use of the plane-wave approximation of the ejected electron wave function combined with the Hartree-Fock frozen-core approximation of the Dyson orbital is also considered and its results are compared with those of our methods and with experiment. A good agreement between the calculated photodetachment cross sections and the experimental data is obtained for O 2 − and CN − when using the three methods. For OH − , the calculated scattering-wave electron photodetachment cross sections agree well with two most recent sets of experimental data among the three available while the plane-wave results disagree with all the experimental and theoretical data. The different approaches to calculate the Dyson orbital are also discussed as well as the convergence of the calculations with respect to the choice of the one-electron basis set. The approximation of Dyson orbitals by Kohn-Sham orbitals appears to overestimate the photodetachment cross section.
Rate coefficients for state-to-state rotational transitions of C 3 N − induced by collision with both orthoand para-H 2 are presented. Quantum calculations are performed at the closecoupling level using the uniform J-shifting method and a new potential energy surface specially developed for this purpose. Rate coefficients are obtained for state-to-state transitions among the first 28 rotational levels of C 3 N − and for temperatures ranging from 10 to 300 K. The para-H 2 rate coefficients are shown to differ strongly from the mass-scaled He rate coefficients previously computed. The orthoand para-H 2 rate coefficients are very similar, as it was already observed for the rotational transitions of CN − and C 6 H − . There is also an unexpected similarity between the rates coefficients of the rotational de-excitations of CN − , C 3 N − , and C 6 H − . This may open to door to quantitative extrapolations of the rate coefficients for larger anions.
Quantum tunneling is a common fundamental quantum mechanical phenomenon. The dynamics induced by this effect is closely connected to the shape of the potentials. Here we treat the CO2-N2 van der Waals complex dynamics using a first principles treatment where nuclear motions and nuclear spins are fully considered. This dimer is found to exhibit complex spectral and dynamical features that cannot be accounted for using standard experimental and theoretical models. We shed light on some aspects of its quantum tunneling dynamics that remained unexplained since its first evidence 85 years ago. CO2-N2 represents also an important prototype for studying the systematic (as in NH3) lifting of degeneracy due to tunneling effects and large amplitude motions. Vibrational memory and quantum localization effects are evidenced. Plural potential wells separated by potential barriers are commonly found for polyatomic organic and inorganic molecules (e.g., cis-trans isomerization and enol-keto tautomerism). The present findings are useful for understanding the complex quantum effects that may occur there.
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