Computation and analysis of bound vibrational spectra of the neon tetramer using row orthonormal hyperspherical coordinates.

This paper presents the first implementation of the row-orthonormal hyperspherical coordinate formalism for the computation of the vibrational spectrum of a tetratomic system. The wavefunction of Ne is expanded on a large basis set of hyperspherical harmonics generated numerically. This method not only provides spectra with reasonable accuracy, but also gives physical insight into the vibrational dynamics of the system.

Non-adiabatic molecular dynamics investigation of the size dependence of the electronic relaxation in polyacenes.

The Tully's fewest switches surface hopping algorithm is implemented within the framework of the time-dependent density functional based tight binding method (TD-DFTB) to simulate the energy relaxation following absorption of a UV photon by polycyclic aromatic hydrocarbons (PAHs). This approach is used to study the size effect on the ultrafast dynamics in excited states for a special class of PAH species called polyacenes. We determine the dynamical relaxation times and discuss the underlying mechanisms.

Quantum modelling of hydrogen chemisorption on graphene and graphite.

The chemisorption of hydrogen on graphene or graphite is studied within a quantum formalism involving a subsystem coupled to a phonon bath. The subsystem includes the hydrogen atom approaching the surface perpendicularly right on top of a carbon atom which puckers out of the surface. The bath includes the acoustic and optical phonon modes vibrating perpendicularly to the surface.

Photoabsorption spectrum of helium trimer cation--theoretical modeling.

The photoabsorption spectrum of He3(+) is calculated for two semiempirical models of intracluster interactions and compared with available experimental data reported in the middle UV range [H. Haberland and B. von Issendorff, J.

Sticking of hydrogen on supported and suspended graphene at low temperature.

The physisorption of atomic hydrogen on graphene is investigated quantum mechanically using a semiempirical model for the lattice dynamics. A thermally averaged wave packet propagation describes the motion of the H atoms with respect to the membrane. Two graphene configurations, either supported on a silicone oxide substrate or suspended over a hole in the substrate, are considered.

Sticking and desorption of hydrogen on graphite: a comparative study of different models.

We study the physisorption of atomic hydrogen on graphitic surfaces with four different quantum mechanical methods: perturbation and effective Hamiltonian theories, close coupling wavepacket, and reduced density matrix propagation methods. Corrugation is included in the modeling of the surface. Sticking is a fast process which is well described by all methods.

Vibrational spectrum of Ar3(+) and relative importance of linear and perpendicular isomers in its photodissociation.

The photodissociation dynamics of the argon ionized trimer Ar(3)(+) is revisited in the light of recent experimental results of Lepère et al. [J. Chem.

Ab initio study of valence and Rydberg states of CH3Br.

We performed configuration interaction ab initio calculations on the valence and 5s, 5p(a(1)), and 5p(e) Rydberg bands of the CH(3)Br molecule as a function of the methyl-bromide distance for frozen C(3v) geometries. The valence state potential energy curves are repulsive, the Rydberg state ones are similar to the one of the CH(3)Br(+) ion with a minimum at short distance. One state emerging from the 5p(e) band has valence and ion-pair characters as distance increases and the corresponding potential curve has a second minimum at large distance.

Ab initio study of methyl-bromide photodissociation in the A band.

We performed a theoretical study of the photodissociation dynamics of CH(3)Br in the A band using a wave packet propagation technique on coupled ab initio potential energy curves. The present model involves the (3)Q(1) and (1)Q(1) excited states which can be populated from the ground state by a perpendicular transition and which are correlated at large methyl-bromide distance to the ground bromide spin-orbit state, as well as the (3)Q(0) and 4E states which can be excited by a parallel and perpendicular transition (respectively) and both correlate to excited Br(*) spin-orbit state. The model provides absorption cross sections and branching ratios in excellent agreement with experimental results.

The H(3) (+) rovibrational spectrum revisited with a global electronic potential energy surface.

In this paper, we have computed the rovibrational spectrum of the H(3) (+) molecule using a new global potential energy surface, invariant under all permutations of the nuclei, that includes the long range electrostatic interactions analytically. The energy levels are obtained by a variational calculation using hyperspherical coordinates. From the comparison with available experimental results for low lying levels, we conclude that our accuracy is of the order of 0.

Modeling of HeN+ clusters. II. Calculation of He3+ vibrational spectrum.

We have computed the vibrational spectrum of the helium ionized trimer He(3)(+) using three different potential energy surfaces [D. T. Chang and G.

Ab initio vibrational predissociation dynamics of He-I2(B) complex.

Three-dimensional quantum mechanical calculations on the vibrational predissociation dynamics of HeI2 B state complex are performed using a potential energy surface accurately fitted to unrestricted open-shell coupled cluster ab initio data, further enabling extrapolation for large I2 bond lengths. A Lanczos iterative method with an optimized complex absorbing potential is used to determine energies and lifetimes of the vibrationally predissociating He,I2(B,v') complex for v' View Article and Find Full Text PDF

Calculation of argon trimer rovibrational spectrum.

Rovibrational spectra of Ar3 are computed for total angular momenta up to J=6 using row-orthonormal hyperspherical coordinates and an expansion of the wave function on hyperspherical harmonics. The sensitivity of the spectra to the two-body potential and to the three-body corrections is analyzed. First, the best available semiempirical pair potential (HFDID1) is compared with our recent ab initio two-body potential.

Numerical generation of hyperspherical harmonics for tetra-atomic systems.

A numerical generation method of hyperspherical harmonics for tetra-atomic systems, in terms of row-orthonormal hyperspherical coordinates-a hyper-radius and eight angles-is presented. The nine-dimensional coordinate space is split into three three-dimensional spaces, the physical rotation, kinematic rotation, and kinematic invariant spaces. The eight-angle principal-axes-of-inertia hyperspherical harmonics are expanded in Wigner rotation matrices for the physical and kinematic rotation angles.

Competition between adiabatic and nonadiabatic fragmentation pathways in the unimolecular decay of the ArI2(B) van der Waals complex.

The competition between vibrational and electronic predissociations of the ArI2(B) van der Waals complex has been studied using several dynamical computational methods: exact quantum wave-packet propagation, time-dependent golden rule, and quasiclassical trajectory with quantum jumps model. Five electronic states are considered using recent three-dimensional coupled surfaces obtained with a perturbative diatoms-in-molecules method. Final vibrational and electronic populations, predissociation rates, and absorption spectra have been computed for I2(B,v=18-24)<--I2(X,v=0) excitations within the complex.

Quantum studies of H atom trapping on a graphite surface.

The trapping and sticking of H and D atoms on the graphite (0001) surface is examined, over the energy range of 0.1-0.9 eV.