Patricia Barragán

Full-dimensional (15-dimensional) ab initio analytical potential energy surface for the H7+ cluster

Full-dimensional ab initio potential energy surface is constructed for the H(7)(+) cluster. The surface is a fit to roughly 160,000 interaction energies obtained with second-order MöllerPlesset perturbation theory and the cc-pVQZ basis set, using the invariant polynomial method [B. J. Braams and J. M. Bowman, Int. Rev. Phys. Chem. 28, 577 (2009)]. We employ permutationally invariant basis functions in Morse-type variables for all the internuclear distances to incorporate permutational symmetry with respect to interchange of H atoms into the representation of the surface. We describe how different configurations are selected in order to create the database of the interaction energies for the linear least squares fitting procedure. The root-mean-square error of the fit is 170 cm(-1) for the entire data set. The surface dissociates correctly to the H(5)(+) + H(2) fragments. A detailed analysis of its topology, as well as comparison with additional ab initio calculations, including harmonic frequencies, verify the quality and accuracy of the parameterized potential. This is the first attempt to present an analytical representation of the 15-dimensional surface of the H(7)(+) cluster for carrying out dynamics studies.

Energetics and solvation structure of a dihalogen dopant (I2) in 4He clusters

The energetics and structure of small HeNI2 clusters are analyzed as the size of the system changes, with N up to 38. The full interaction between the I2 molecule and the He atoms is based on analytical ab initio He-I2 potentials plus the He-He interaction, obtained from first-principle calculations. The most stable structures, as a function of the number of solvent He atoms, are obtained by employing an evolutionary algorithm and compared with CCSD(T) and MP2 ab initio computations. Further, the classical description is completed by explicitly including thermal corrections and quantum features, such as zero-point-energy values and spatial delocalization. From quantum PIMC calculations, the binding energies and radial/angular probability density distributions of the thermal equilibrium state for selected-size clusters are computed at a low temperature. The sequential formation of regular shell structures is analyzed and discussed for both classical and quantum treatments.

A study of conical intersections for the H3(+) system.

A parametrization of the three asymptotic conical intersections between the energies of the H3(+) ground state and the first excited singlet state is presented. The influence of an additional, fourth conical intersection between the first and second excited states at the equilateral geometry on the connection between the three conical regions is studied, for both diatomics-in-molecules and ab initio molecular data.

Hyperspherical close-coupling calculations for electron-capture cross sections in low-energy Ne^1^0^++H(1s) collisions (5 pages)

We present total and partial electron-capture cross sections for Ne{sup 10+}+H(1s) collisions at energies from 0.01 eV to 1 keV using the hyperspherical close-coupling method. Good agreements with the previous calculations by the classical-trajectory Monte-Carlo method are found for total capture cross section, but not for partial cross sections, especially below about 200 eV/amu. We found that the total cross section is mainly due to the population of n=7 channels and only at energies above 50 eV/amu n=5,6 channels begin to contribute to the total cross section.

Electron capture in collisions of N2+ and O2+ ions with H(1s) at low impact energies

We present ab initio quantal calculations of electron capture cross sections for collisions of ground and metastable states of {sup 14}N{sup 2+} and {sup 16}O{sup 2+} ions with H(1s), at collision energies 10{sup -2}<E<10{sup 2} eV/amu. The calculation for N{sup 2+}+H updates the previous one of Barragan et al. [Phys. Rev. A 70, 022707 (2004)] at 0.1<E<0.3 eV/amu. Total cross sections for both systems show large values of about 5x10{sup -15} cm{sup 2} at E<0.1 eV/amu, where they exhibit resonant structures.

Infrared spectrum of H{sub 5}{sup +} and D{sub 5}{sup +}: The simplest shared-proton model

This work has been supported by the Consolider-Ingenio 2010 Programme CSD2009-00038 (MICINN), MICINN Grant No. FIS2010-18132, and CAM Grant No. S-2009/MAT/1467. P.B. acknowledges support from the “Fundacion Ram ´ on Areces.” The aid of COST Action ´ CM1002 (CODECS) is also appreciated.