Spectroscopy of weakly-bound complexes in highly excited electronic states: the HeI2(E3g) ion-pair state

1 pag.; 2 figs. XXVIII International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2013) IOP PublishingThe study of electronically excited van der Waals (vdW) systems presents a challenge for the theory of intermolecular interactions, and here we show how far ab initio computations can go. We found that the interaction energies for such electronically excited systems can indeed be determined, providing a reliable and accurate description for the E state potential of the HeI2, that in combination with the ground X and electronic excited B state of the complex, is useful to model experimental data related with potential minima and also predict higher vibrational vdW states.Peer Reviewe

Revisiting the symmetry breaking in the (X)over-tilde(2)Sigma(+)(u) state of BNB

In agreement with our previous work [A. Kalemos, J. Chem. Phys. 138, 224302 (2013)], we established the centrosymmetric nature of the ground BNB state by means of the Restricted Coupled Cluster Singles and Doubles + Perturbative Triples (RCCSD(T)) computational method. We have also studied the symmetry adapted or broken behavior at the Configuration Interaction Singles and Doubles (CISD), CISD + Davidson Correction (CISD + Q), and RCCSD(T) computational levels based on various solutions of the Restricted Hartree-Fock (RHF) equations. Our theoretical conclusions are in agreement with the experimental results concerning the structure of the titled species. Published by AIP Publishing

Some ab initio thoughts on the bonding in O3H

We study the groundstate of O3H (= OaObOcH) with single (RCCSD(T)) and multi (MRCI) reference correlation methods in order to shed some light on its bonding mechanism in connection with its low dissociation energy and rather long bond distance (OaOb-OcH). For such a task all three dissociation/formation paths were considered (O-2 + OH, O + O2H, and O-3 + H) and the associated nonadiabatic coupling matrix elements were examined. It appears that the excited states of the above asymptotic fragments participate in the equilibrium wavefunction of O3H in a way that results in a symmetry broken structure

Theoretical investigation of the He-I 2(E 3Π g) ion-pair state: Ab initio intermolecular potential and vibrational levels

We present a theoretical study on the potential energy surface and vibrational bound states of the E electronic excited state of the HeI 2 van der Waals system. The interaction energies are computed using accurate ab initio methods and large basis sets. Relativistic small-core effective core potentials in conjunction with a quintuple-zeta quality basis set are employed for the heavy iodine atoms in multireference configuration interaction calculations for the 3A ′ and 3A ″ states. For the representation of the potential energy surface we used a general interpolation technique for constructing potential surfaces from ab initio data based on the reproducing kernel Hilbert space method. The surface presents global and local minima for T-shaped configurations with well-depths of 33.2 and 4.6cm -1, respectively. Vibrational energies and states are computed through variational quantum mechanical calculations. We found that the binding energy of the HeI 2(E) T-shaped isomer is 16.85cm -1, in excellent agreement with recent experimental measurements. In lieu of more experimental data we also report our predictions on higher vibrational levels and we analyze the influence of the underlying surface on them. This is the first attempt to represent the potential surface of such a highly excited electronic state of a van der Waals complex, and it demonstrates the capability of the ab initio technology to provide accurate results for carrying out reliable studies to model experimental data. © 2012 American Institute of Physics.This work has been supported by the MICINN Grant Nos. FIS2010-18132 and FIS2011-29596-C02-01.Peer Reviewe

Electronic structure and bonding of ozone

The ground and low-lying states of ozone (O(3)) have been studied by multireference variational methods and large basis sets. We have constructed potential energy curves along the bending coordinate for (1,2) (1)A’, (1,2) (1)A ‘’, (1,2) (3)A’, and (1,2) (3)A ‘’ symmetries, optimizing at the same time the symmetric stretching coordinate. Thirteen minima have been located whose geometrical and energetic characteristics are in very good agreement with existing experimental data. Special emphasis has been given to the interpretation of the chemical bond through valence-bond-Lewis diagrams; their appropriate use captures admirably the bonding nature of the O(3) molecule. The biradical character of its ground state, adopted long ago by the scientific community, does not follow from a careful analysis of its wave function. (C) 2008 American Institute of Physics

Spectroscopy of weakly-bound complexes in highly excited electronic states: the He-I-2(E-3 Pi(g)) ion-pair state

The study of electronically excited van der Waals (vd) systems presents a challenge for the theory of intermolecular interactions, and here we show how far ab initio computations can go. We found that the interaction energies for such electronically excited systems can indeed be determined, providing a reliable and accurate description for the E state potential of the HeI2,, that in combination with the ground X and electronic excited B state of the complex, is useful to model experimental data related with potential minima and also predict higher vibrational vdW states