Volume 129, Issue 8, 28 August 2008
Index of content:
129(2008); http://dx.doi.org/10.1063/1.2965905View Description Hide Description
The Wang–Landau sampling method is adapted to the calculation of quantum densities of states for fully coupled anharmonic systems. The accuracy of the method is illustrated against exact counting for two molecules with separable oscillators, namely, the Zundel complex and the cluster. Application to the fully coupled naphthalene molecule reveals significant deviations in the finite temperature thermodynamicalproperties that are not captured by simple perturbation theory. There are no limitations in the size of the molecules that can be treated with this method.
Anomaly of the rotational nonergodicity parameter of glass formers probed by high field electron paramagnetic resonance129(2008); http://dx.doi.org/10.1063/1.2973660View Description Hide Description
Exploiting the high angular resolution of high field electron paramagnetic resonance measured at 95, 190, and 285 GHz we determine the rotational nonergodicity parameter of different probe molecules in the glass former -terphenyl and polybutadiene in a model-independent way. Our results clearly show a characteristic change in the temperature of the nonergodicity parameter proving a rather sharp dynamic crossover in both systems, in contrast to previous results from other techniques.
129(2008); http://dx.doi.org/10.1063/1.2976563View Description Hide Description
The quantum state-resolved reactivity of on has been measured for the first time for two vibrationally excited Si–H stretch local mode states ( and ) as well the ground state as a function of translational energy and surface temperature . We observe evidence for both direct and precursor-mediated chemisorption pathways. As expected, increasing (or ) decreases for the precursor-mediated reaction and increases for the direct chemisorption. However, vibrational excitation of the incident increases for both the direct and the precursor-mediated pathway with a higher for the state than for the state, indicating a nonstatistical reaction mechanism.