Volume 129, Issue 17, 07 November 2008
Index of content:
129(2008); http://dx.doi.org/10.1063/1.3001918View Description Hide Description
The photodissociationdynamics of chlorine azide at the 157 nm region was studied theoretically using the multireference configuration interaction method and the complete active space self-consistent field direct dynamics method. The excitation at the 157 nm region was assigned to the transition. A likely pathway for the formation of cyclic after this transition was identified by direct dynamics as follows: excited to dissociates after about 40 fs to excited , with about 44 kcal/mol internal energy). This vibrationally hot goes diabatically through a conical intersection with at 44 fs onto . At 19 fs later and repeatedly after every 55 fs, crosses and trickles down via Coriolis coupling to state, which has a potential minimum at the cyclic- structure. Some fraction of produced will survive dissociation and will be found as the cyclic , and some other fraction will eventually dissociate to over a high barrier found previously.
129(2008); http://dx.doi.org/10.1063/1.3020350View Description Hide Description
The diffusion of long -alkanes confined in silicalite zeolite has been studied with the neutron spin-echo technique. Since only isotropic diffusion has been measured so far with this technique, we derive the intermediate scattering functions for one-dimensional (1D) and single-file diffusion. The 1D diffusion model explains the results obtained for long -alkanes in the intersecting channel system of silicalite. A redistribution of the molecules is observed at high temperatures, supporting the presence of internal barriers within the zeolite crystals.
129(2008); http://dx.doi.org/10.1063/1.3020717View Description Hide Description
Recent experiments and classical molecular dynamics simulations performed on liquidHg near melting have suggested the existence of two processes with different time scales in its single-particle dynamics. We report a study of this system by using ab initiomolecular dynamics simulations, which recover the same kind of behavior, and we analyze it in terms of a theoretical approach, which clarifies its origin. We show that the previous interpretation has been induced by the unphysical extension of the diffusive model to short times. Moreover, we also find that quite different liquid metals, such as Si and Mg, also exhibit a similar behavior as Hg, with the only difference being in the time scales involved due to the different masses and interactions.
129(2008); http://dx.doi.org/10.1063/1.3013559View Description Hide Description
A generalized effective fitting Hamiltonian is tested against a modelsystem of highly excited coupled Morse oscillators. At energies approaching dissociation, a very few resonance couplings in addition to the standard 1:1 and 2:2 couplings of the Darling–Dennison Hamiltonian suffice to fit the spectrum and match the large-scale features of the mixed regular and chaotic phase spaces, consisting of resonance zones organized around periodic orbits of low order that break the total polyad action.