No abstract

We present a joint experimental and theoretical investigation of the linear and nonlinear optical response of butadiyne-linked zinc porphyrin oligomers. Efficient overlap between the chromophores leads to a large red-shift of the Q absorption band together with a splitting of the B band into two components when increasing the chain length from one to two repeating porphyrin units. Ultrafast pumb-probe measurements performed on these compounds show several well-defined features, associated with singlet excited state absorption. We also find clear evidence for the formation of longer-lived triplet excitons, resulting from very efficient singlet-triplet intersystem crossing processes. For the monomers, the assignment of the observed linear and photoinduced absorption features is supported by a Configuration Interaction description of the singlet and triplet excited states. In the case of the porphyrin dimer, agreement with the experimental results can only be obtained by considering a sizable cumulenic contribution in the excited-state geometry used as input for the CI calculations. The potential of porphyrin systems for Reverse Saturable Absorption and Nonlinear Optics is emphasized.

No abstract

Communications ADVANCED MATERIALS Fig. 3. Powder X-ray diffraction data for the palbadiUm-Siher alloy film deposited at a preheating temperature of 80°C and substrate temperature of 250 "C on an SiO, substrate. The lines marked "0" and " " are at the 20 positions of authentic. crystalline Ag and Pd, respectively. Peaks marked "*" are due to the Ag/Pd film; all other peaks are derived from the substrate. grain sizes of 0.1 -0.2 pm and were deposited at a deposition rate of 230 Ajmin. X-ray powder diffraction data showed the presence of CuPd alloy together with (1 11) oriented Cu as expected based on the binary alloy phase diagram.[221 Silver-copper alloy films were deposited under the same conditions with a deposition rate of approximately 180 A/ min. Powder X-ray diffraction data show the presence of Ag/Cu alloy with a (1 11) preferential orientation consistent with the binary alloy phase diagram.[22]In summary, the AACVD of crystalline silver, palladium and binary metal alloys of Pd/Ag, Pd/Cu and Ag/Cu has been demonstrated. Aerosol-assisted CVD has the following potential advantages over traditional precursor delivery methods: (i) higher deposition rates, (ii) transport of thermally sensitive compounds and (iii) reproducible deposition of binary materials. The generality of this technique for other metals and a quantitative description of the deposition of binary metal alloys is being investigated.

No abstract