Index of content:
Volume 117, Issue 1, 01 July 2002
Quantum chemical study of π–π stacking interactions of the bacteriochlorophyll dimer in the photosynthetic reaction center of Rhodobacter sphaeroides117(2002); http://dx.doi.org/10.1063/1.1487831View Description Hide Description
Intermolecular π–π stacking interactions of the bacteriochlorophyll dimer in the photosynthetic reaction center of the purple bacterium Rhodobacter sphaeroides were analyzed by the second order Møller–Plesset perturbation method using the modified 6-31G*(0.25) basis set with diffuse d-polarization by Hobza and co-workers. MP2/6-31G*(0.25) calculations yield an intermolecular interaction energy of −21.50 kcal/mol for the bacteriochlorophyll dimer. Thus, the attractive nature of the π–π stacking interaction of the bacteriochlorophyll dimer in the photosynthetic reaction center from Rhodobacter sphaeroides is, for the first time, firmly established.
Depolarization as a probe for ultrafast reorientation of diatomics in condensed phase: ClF versus in rare gas solids117(2002); http://dx.doi.org/10.1063/1.1486444View Description Hide Description
Polarization dependent femtosecond pump-probe spectra display characteristic vibrational wave packet dynamics of ClF in Ar (isotropic cage and small fragment size) and in Kr (cylindrical cage and large fragments). The intensity ratio of the signals for pumping with parallel versus crossed polarization with respect to the probe pulse is close to the value 1/3, as expected for full photoselection immediately after excitation. For ClF this ratio depolarizes to unity within showing the ultrafast randomization of the orientation of the molecular bond due to fragment scattering off the matrix cage. The direction of the bond is geometrically fixed by the Kr matrix and the ratio remains constant.
Structure of the exact wave function. V. Iterative configuration interaction method for molecular systems within finite basis117(2002); http://dx.doi.org/10.1063/1.1487830View Description Hide Description
The iterative configuration interaction (ICI) method is applied to molecular systems within finite basis using only few (1–3) variables and shown to give the exact results that are identical to the full CI (FCI) ones. Since each iteration step of ICI is variational, the ICI converges monotonically to the exact solution from above. The diagonalization in ICI is so slight as the number of variables is so small, in contrast to the huge number of variables of FCI. We calculated the molecular ground states of various spin-space symmetries using minimal basis and double zeta basis. The number of iterations for convergence was small for minimal basis but moderate for double zeta basis, considering that only 1–3 variables are optimized in each iteration step.