This work deals with the study of the role of intra-gap density of states on the colour selection of the collection spectrum of glass/ITO/a-Six:C1-x:H/Al Schottky photodiodes. In order to optimise the voltage colour selection and to study the influence of intragap density of states in the final device performances, different undoped a-Six:C1-x:H films (1 μm thick) have been produced in a conventional Plasma Enhanced Chemical Vapour Deposition (PECVD) system using silane and a controlled mixtures of silane and methane as gas sources. The properties of the films were analysed by dark conductivity measurements, infrared spectroscopy, visible spectroscopy and constant photocurrent method (CPM), to determine the valence controllability and to correlate the silicon carbide layer composition with the performances of the devices. The performances obtained concerning the spectral response of the devices were correlated with the carbon content and the density of states of the a-Six:C1-x:H films.

The new compound [Co(eta(5)-C5H5)(dppf-P,P')I]I, 1, was synthesised by the stoichiometric reaction of the Co(III) complex [Co(eta(5)-C5H5)(CO)I-2], 2, with 1,1'-bis(diphenylphosphino)ferrocene (dppf) in CH2Cl2, and was characterised by multinuclear NMR spectroscopy. Exposure to air of THF or CH2Cl2 solutions of compound 1 gave, in an unexpected way, a polymeric chain comprising bridging 1,1'-bis(oxodiphenylphosphoranyl) ferrocene (dppfO(2)) joining tetrahedral Co(II) units [CoI2(mu-dppfO(2))](n), 3. Attempts to obtain the polymeric chain 3 by the direct reaction of dppfO(2) with CoI2, in CH2Cl2, gave instead the monomeric compound [CoI2(dppfO(2))], 4, in which dppfO2 is coordinated in a chelating mode. The structural characterisation of compounds 2, 3, and 4 was carried out by single crystal X-ray diffraction studies. The magnetic behaviour of [CoI2(dppfO(2))] and [CoI2(mu-dppfO(2))](n) was studied, and the results are consistent with tetrahedral S = 3/2 Co-II, possessing a (4)A(2) ground state, and S = 0 Fe-II. In these compounds, Co-II negative zero field splittings were determined from an analysis of the magnetic susceptibility temperature dependence, with D/k = -13 and -14 K for CoI2(dppfO(2)) and [CoI2(mu-dppfO(2))](n), respectively. DFT calculations were performed in order to understand the electronic structure of [Co(eta(5)-C5H5)(dppf-P,P')I]I, 1, as well as that of the paramagnetic specie [CoI2(dppfO(2))], 4. The [CoI2(mu-dppfO(2))](n) chain was also analysed and found to behave very similarly to the monomeric iodine derivative 4. The calculations showed the unpaired electrons to be localized on the Co(II) centre in all these species. The rather complicated electrochemical behaviour exhibited by the dppf complex [Co-III(eta(5)-C5H5)(dppf-P,P')I]I and by [Co(dppfO(2))I-2] is discussed.

For the study of astrophysically relevant capture reactions in the underground laboratory LUNA a new setup of high sensitivity has been implemented. The setup includes a windowless gas target, a 4$π$ BGO summing crystal, and beam calorimeters. The setup has been recently used to measure the d(p,$\gamma$)3He cross-section for the first time within its solar Gamow peak, i.e. down to 2.5keV c.m. energy. The features of the optimized setup are described. © 2002 Elsevier Science B.V. All rights reserved.

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The reactivity of mono-substituted HC=CR (R =Ph. a; CH2OH, b; CH2CH2CH2CH3, c) and di-substituted RC=CR (R = CH2CH3, d; CO2CH3, e; Ph. f) acetylenes was studied in supercritical carbon dioxide (scCO(2)) using the easily available complex CpCo(CO)(2) as catalyst. The reaction of phenylacetylene produced a mixture of the isomeric cyclotrimers 1,3,5- (2a) and 1.2,4-triphenylbenzene (2a '). in a 1:5 ratio, and traces of cobaltcyclopentadienone complexes CPCO(eta (4)-C4H2[Ph](2)CO) (6a, mixture of isomers). The possible product formed by the incorporation of CO, to alkynes, i.e. diphenylpyrone (7a) was not observed. The reaction of the cobaltacyclopentadiene complex CpCo(1.4-sigma -C-4[Ph](4))(PPh)(3) (8f), in scCO(2), was performed. No insertion of CO2 into the Co-C a-bond to form tetraphenylpyrone (7f) by reductive elimination was observed, instead the cobaItcyclobutadiene Complex CpCo(eta (4)-C-4[Ph](4)) (9f) was formed. In the reactions with other alkynes, lower yields were obtained in general, except in the cyclotrimerisation of the highly activated alkyne, propargyl alcohol (b). Reaction of the non-activated alkynes, 1-hexyne (c) and 3-hexyne (d), produced complex mixtures of cobalt complexes in low yield in which the alkyne was coordinated to cobalt. Finally, the highly hindered diphenylacetylene (f) gave a mixture of the known Complexes CpCo(eta (4)-C-4[Ph](4)) (9f) and CpCo(eta (4)- C-4[Ph](4)CO) (6f) in agreement with the results observed in conventional organic solvents. (C) 2001 Elsevier Science B.V, All rights reserved.