Index of content:
Volume 125, Issue 23, 21 December 2006
125(2006); http://dx.doi.org/10.1063/1.2408412View Description Hide Description
A new band system of , is observed by laser induced fluorescencespectroscopy, constituting the first direct detection of the state of . Observations were made by laser excitation of , produced in an acetylene discharge, to the level, followed by detection of Swan band fluorescence. Rotational analysis of this band yielded rotational constants for the state: , and . The vibrational band origin was determined to be .
125(2006); http://dx.doi.org/10.1063/1.2408411View Description Hide Description
By using the multiconfigurational second-order perturbation method CASPT2, including corrections for the basis set superposition error, the lowest-singlet excited state of the face-to-face -stacked cytosine homodimer is revealed to be bound by about half an eV, being the source of an emissive feature consistent with the observed redshiftedfluorescence.
125(2006); http://dx.doi.org/10.1063/1.2400851View Description Hide Description
In recent years there has been a resurgence of interest in Bohmian mechanics as a numerical tool because of its local dynamics, which suggest the possibility of significant computational advantages for the simulation of large quantum systems. However, closer inspection of the Bohmian formulation reveals that the nonlocality of quantum mechanics has not disappeared—it has simply been swept under the rug into the quantum force. In this paper we present a new formulation of Bohmian mechanics in which the quantum action, , is taken to be complex. This leads to a single equation for complex , and ultimately complex and but there is a reward for this complexification—a significantly higher degree of localization. The quantum force in the new approach vanishes for Gaussian wave packet dynamics, and its effect on barrier tunneling processes is orders of magnitude lower than that of the classical force. In fact, the current method is shown to be a rigorous extension of generalized Gaussian wave packet dynamics to give exact quantum mechanics. We demonstrate tunneling probabilities that are in virtually perfect agreement with the exact quantum mechanics down to calculated from strictly localized quantum trajectories that do not communicate with their neighbors. The new formulation may have significant implications for fundamental quantum mechanics, ranging from the interpretation of non-locality to measures of quantum complexity.