The photodissociation spectroscopy and dynamics of the methoxy radical Ã(A1) r X̃(2E) transition have been investigated using fast radical beam photofragment translational spectroscopy. The à state of both CH3O and CD3O is observed to predissociate via curve crossings with one or more repulsive electronic states. The photofragment yield spectrum consists of the C-O stretch progression and combin...

(Received December, 1988) The adaptive umbrella sampling technique, introduced recently to improve the probability ratio method and found to perform more reliably then the customary harmonic umbrella sampling, is tested and compared with other free energy methods. One of the tests applies the method to a transition involving a chemical change: calculation of the hydration free energy difference...

The relative free energias of hydration of dimethyl phosphate anion in gauchegauche, gauchetrans, and trans-trans conformations of phosphodiester torsion angles, computed with Monte Carlo method in the (T, V, N) ensemble at 25 OC, are reported. The free energy differences are determined by the probability ratio method using both umbrella sampling with harmonic weighting functions and adaptive u...

In a previous article we introduced a reaction coordinate based on the unstable normal mode at the saddle point of the potential energy surface. We here calculate the free-energy distribution along this coordinate for the isomerization of calix@4#arene in vacuo and in chloroform using umbrella sampling, with one umbrella covering the entire range of the reaction coordinate. An excellent first g...

Negative linear compressibility (NLC), a rare and important mechanical effect with many application potentials, in a crystal of α-BiB3O6 (BIBO) is comprehensively investigated using first-principles calculations and high-pressure synchrotron X-ray diffraction experiments. The results indicate that the BIBO crystal exhibits the second largest NLC among all known inorganic materials over a broad ...

This contribution deals with the blocking probability in a hierarchical network. In the considered model, a continuous coverage is made with micro-cells that accommodate both fresh calls and handover requests. Over this micro-cell coverage, umbrella-cells are implemented. These umbrella-cells only accept handover requests that cannot be managed by micro-cells. This hierarchy enables to reduce t...