Simulation of the infrared predissociation spectra of H5+

Abstract

A quantum study of the bound states and infrared predissociation spectra of H 5 + is done using a recently proposed global and accurate potential-energy surface [Aguado et al., J. Chem. Phys. 133, 024306 (2010)]. The bound states are calculated for seven degrees of freedom using an iterative Lanczos method, yielding a dissociation energy in very good agreement with the available experimental data. The predissociation states are described by a wave-packet treatment considering a shared-proton model, in which the three-dimensional motion of the central atom is described using non-Jacobi bond coordinates. The justification of this model is that the change in the electric dipole moment is larger as a function of the motion of the central atom, responsible for the proton transfer in the H 3 + + H 2 → H 2 + H 3 + reaction. The electric dipole moment is calculated at the level of coupled-cluster theory with single and double excitations and fitted in nine dimensions to an analytical function. With it, the infrared predissociation spectrum is simulated, yielding a reasonable agreement with recent measurements.

Infrared spectrum of H5+and D5+: The simplest shared-proton model

“…To date, several full dimensional potential energy surfaces (PESs) for H 5 + are available [8][9][10]. In this Rapid Communication we use the accurate triatomics in molecules based analytical PES [9], fitted to high-level ab initio points [11], together with the electric dipole moment surface recently reported and used to perform spectra simulations at zero temperature [12]. To just account for the proton transfer between the two H 2 moieties, we present an extremely simplified two-dimensional (2D) model which incorporates the effect of the temperature.…”

“…The dipole moment surface μ(r,R) was also analytically fitted to the ab initio values [12]. At each R, it resembles a hyperbolic tangent as a function of r, that is, an odd function, and the corresponding transition dipole moments μ v n ;vn = v n |μ| vn vanish unless the v ,v states are of different symmetry.…”

Dynamically biased statistical model for the ortho/para conversion in the ${\rm H}_2 + {\rm H}_3^+$H2+H3+ → ${\rm H}_3^{+} +$H3++ H2 reaction

“…[59][60][61]65 If the hypothesis discussed above is true, there may be some differences in the broadening of the resonances near the dissociation threshold as a function of the total angular momentum excitation, and this could be probably measured by changing the experimental rotational temperature of the experiments. Also, there have been several theoretical simulations on this infrared predissociation spectra, 44,61,62 but they use either approximate methods or reduced dimensionality models which need to be improved to account for the narrow resonances at high J with enough accuracy to extract information relevant for the transition between statistical and direct regimes in the collisions discussed in this work.…”

“…The experimental value at 135 K of Crabtree et al 17 is much lower than the one obtained here, and very close to the statistical limit. In order to improve the present results, quantum cal- [59][60][61] Recently, several quantum approximate and/or reduced dimensionality simulations of the predissociation spectrum have been performed 44,61,62 providing some physical assignment. The agreement between experiment and theory is still quite poor, what demonstrate the need of designing new quantum methods to include all degrees of freedom and the permutation symmetry in this problem.…”

Dissociative recombination and excitation of D5+by collisions with low-energy electrons

“…The spectroscopic work and the fact that H 5 + is * Corresponding author. Email: mats.larsson@fysik.su.se the simplest molecule containing five atoms and the simplest system with two neutrals combined by a proton have stimulated much theoretical work [11][12][13][14][15][16][17][18][19].…”