Fluorescent tetraruthenated porphyrins embedded in monolithic SiO2 gels by the sol-gel process

In this work silica gels have been prepared by a sol-gel method using tetraethylorthosilicate as gel precursor. The tetraruthenated porphyrins H2(3-TRPyP), Co(3-TRPyP), and H2(4-TRPyP) were incorporated into the systems during gel formation without problems commonly found in the process, such as aggregation. Spectroscopic studies of the resulting silica gels revealed the presence of absorption bands in the range 200-400 nm associated with the transitions of the groups ruthenium-bipyridine, along with the Soret band at the same wavelengths observed in solution. The porphyrins were found to preserve fluorescence emission properties in the range 650-700 nm even after the aging period. Study of the thermal behavior and decomposition kinetics evidenced that the porphyrin H2(4-TRPyP) is the least stable of the group and that all compounds decompose according to first-order kinetics.     

Coulomb excitation of the even-mass selenium nuclei

The properties of the low-lying states of the doubly even selenium nuclei have been investigated via multiple Coulomb excitation effected with 39.2 MeV oxygen projectiles. The excitation probabilities of the first 2⁺ states of ⁷⁶Se, ⁷⁸Se and ⁸⁰Se have been determined directly by resolving inelastically and elastically scattered ⁴He projectiles on thin targets. These measurements yielded values of B(E2; 0⁺ → 2⁺) equal to $\text{0.421 ± 0.009 (}{}^{76}\text{Se}\text{), 0.321 ± 0.009 (}{}^{78}\text{Se}\text{)}\text{and}\text{0.248 ± 0.005 (}{}^{80}\text{Se}\text{) e}{}^2\text{· b}{}^2$. The multiple Coulomb excitation experiments enabled us to detect 2⁺ and 4⁺ levels in all isotopes studied up to 2.1 MeV. Moreover the double Coulomb excitation of 0⁺' states at 854.1 keV (⁷⁴Se), 1498.5 keV (⁷⁸Se), and 1478.3 keV (⁸⁰Se) was also observed. The enhancement of the E2 transition between these 0⁺' levels and the first 2⁺ states decreases rapidly with the increase of the neutron number, i.e., $\text{B(}\text{E}\text{2; 0}{}^{\mathrm{+}}\text{′ → 2}{}^{\mathrm{+}}\text{)/B(}\text{E}\text{2; 2}{}^{\mathrm{+}}\text{→ 0}{}^{\mathrm{+}}\text{) = 2.04 ± 0.08 (}{}^{74}\text{Se}\text{), 0.91 ± 0.08 (}{}^{78}\text{Se),}\text{and}\text{0.28 ± 0.04 (}{}^{80}\text{Se}\text{)}$. States interpreted as the result of direct E3 Coulomb excitation have been observed at 2350.2, 2429.2, 2507.6, and 2717.6 keV in ⁷⁴Se, ⁷⁶Se, ⁷⁸Se and ⁸⁰Se, respectively. Their B(E3; 0⁺ → 3^?) values are $\text{2.1 ± 0.5 (}{}^{74}\text{Se}\text{), 4.0 ± 0.5 (}{}^{76}\text{Se}\text{), 2.7±0.3 (}{}^{78}\text{Se}\text{)}\text{and}\text{0.9 ± 0.2 ( × 10}{}^{\mathrm{?2}}\text{e}{}^2\text{·}\text{b}{}^3$ which represent enhancements of 9.2 ± 2.2, 16.6 ± 2.1, 10.8 ± 1.2 and 3.2 ± 0.7 respectively. Furthermore, angular distribution measurements of γ-rays following Coulomb excitation with 42 MeV ¹⁶O ions in ⁷⁸Se and ⁸⁰Se have been performed. The E2 content of the 2⁺' → 2⁺ transition in these two nuclei is 87.9 % (⁷⁸Se), and 96.2 % or 33.5 % (⁸⁰Se).