Structure and potential energy surface for Na⁺．N₂

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Theoretical Investigation of the Infrared Spectra of the H 5

Reduced dimensional quantum dynamics calculations of the infrared spectrum of the H5 + and D5 + clusters are reported in both low, 300-2200 cm-1, and high, 2400-4500 cm -1, energy regions. The proposed four-dimensional quantum model describes the motion of the proton between the two vibrating hydrogen molecules. The simulations are performed using time-dependent and time-independent approaches within the multiconfiguration time-dependent Hartree method. Propagation of the wavepackets includes an absorbing scheme to deal with vibrational dissociating states, and to assign the different spectral lines, block improved relaxation computations are performed for both bound and predissociative vibrational states of the systems. The reported computations make use of an analytical ab initio-based potential energy, and >on the fly> DFT dipole moment surfaces. The predominant features in the spectra are assigned to the excitations of the shared-proton stretch mode, and above dissociation the symmetric and antisymmetric stretching of the two H2 and the breathing mode of H3 + are also involved. The computed infrared absorption spectra for both cations are in very good agreement with the recent experimental measurements available from multiple-photon dissociation and mass-selected single-photon photodissociation spectroscopy techniques. Comparison of the present results with previous theoretical calculations on these systems is also presented. Such comparisons between different theoretical approaches and experimental measurements can serve to evaluate the approximations employed, and to guide higher-order computations. © 2013 American Chemical Society.This work has been supported by the MICINN grants FIS2010- 18132 and FIS2011-29596-C02-01, Consolider-Ingenio 2010 Programme CSD2009-00038 (MICINN), and COST Action CM1002 (CODECS).Peer Reviewe

Potential energy and transition dipole moment functions of C-2(-)

The potential energy curves of C2- in its 2 Sigma g+, 2 Pi and 2 Sigma u+ states are constructed by morphing the appropriate icMRCI ab initio curves within the framework of the reduced potential curve (RPC) approach of Jenc and Pliva. The actual morphing is performed by fitting the RPC parameters to available experimental data. The resulting potential energy curves are in close harmony with these data thus allowing for evaluation of highly accurate wavefunctions of the observed rovibronic molecular states and for reliable interpolation of the so-far unobserved states. Using these wavefunctions and theoretically evaluated electronic transition moment functions, the dipole moment matrix elements are calculated for the allowed transitions among the studied vibronic states. The 2 Sigma g+ potential energy curve is also used for predicting rotational energies of 13C12C-. The calculated data are believed to be useful in searching for spectral evidence of C2- both in the laboratory and interstellar medium. Several rotational lines of the nu = 0-1 vibronic band of the B22 Sigma u+ rarr X22 Sigma g+ transition are shown to be coincident with absorption features in the spectrum of the carbon star HD 56126