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The photocurrent in conjugated polymer-fullerene blends is dominated by the dissociation efficiency of bound electron-hole pairs at the donor-acceptor interface. A model based on Onsager's theory of geminate charge recombination explains the observed field and temperature dependence of the photocurrent in $\mathrm{P}\mathrm{P}\mathrm{V}\ensuremath{\mathbin:}\mathrm{P}\mathrm{C}\mathrm{B}\mathrm{M}$ blends. At room temperature only 60% of the generated bound electron-hole pairs are dissociated and contribute to the short-circuit current, which is a major loss mechanism in photovoltaic devices based on this material system.

To describe the dynamical interplay of electronic and nuclear degrees of freedom in molecules exposed to strong laser pulses, we present two different variational approaches based on the statonary-action principle: A mean-field treatment of the electron-nuclear interaction and an explicitly correlated ansatz. The two methods are tested on a one-dimensional model of H 2 + which can be solved exactly. The correlated approach significantly improves upon the mean-field treatment, especially in the case of laser fields strong enough to cause substantial dissociation.

The Direct Reaction Field approach is briefly reviewed. Preliminary reports of the calculations on solvent induced shifts in the p * ˆ n transition of acetone in various solvents, and the dissociation of tert-butyl chloride in water are given. q 1999 Elsevier Science B.V. All rights reserved.

One approach to endohedral complexes would comprise controlled opening of the fullerene, encapsulation of the guest material, and restoration of the original fullerene structure, a strategy that Hawkins very likely considered in his pioneering work on osmylation of C{sub 60} and C{sub 70}. Here we report the first regioselective and efficient synthetic method for severing two adjacent bonds in C{sub 60}. Reaction of C{sub 60} with azides yields [5.6]azafulleroids in good yields. In the azafulleroid, one C-C bond is cleaved and the C=C bonds adjacent to the nitrogen atom are susceptible to regiospecific formation of bisazafulleroids. The previously reported elegant work on the self-sensitized photooxygenation of certain C{sub 60} adducts was applied to N-methoxyethoxymethyl (MEM)-substituted [5.6]azafulleroid 1 to afford the ring-opened N-MEM-ketolactam 3 in high yield. Compound 3 is stable under the reaction conditions; no new products were detected after 4 h of photooxygenation in ODCB at 25-30{degree}C. Thereafter, methylene blue was added as a sensitizer, and the photooxygenation was resumed; no further reaction occurred within 5 h. The work presented here can be considered a first step toward the controlled opening of the fullerene cage. 14 refs., 1 fig.

In this work, we report on an investigation of the defect complexes InVe(2)He(n) in tungsten by means of PAC. The release steps InVe(2)He(n), --> InV2Hen-1 + He were identified for n = 1-5. The dissociation energies, in the range of 2.9-4.5 eV, agree perfectly with the values that have been previously determined by means of THDS. The quadrupole frequency is about 122 Mrad/s for n = 1,2 and about 101 Mrad/s for n = 3,4. These values are smaller than the frequency of the undecorated vacancy (n = 0). The vacancy mutates into a divacancy if it is filled with about 10 He atoms, giving rise to a quadrupole frequency of about 218 Mrad/s. This so-called ''trap mutation'' ultimately leads to bubble information. We observed at least three different bubble-associated quadrupole interactions.