http://dspace.bits-pilani.ac.in:8080/jspui/handle/123456789/16938 2026-04-01T10:19:19Z http://dspace.bits-pilani.ac.in:8080/jspui/handle/123456789/20713 Title: Critical Reflection of Neutrons A New Technique for Investigating Interfacial Phenomena Authors: Hayter, J. B; Highfield, R. R; Pullman, B. J Abstract: The possibility of using neutron critical reflection for investigating interfacial phenomena is assessed. Calculations of the reflectivity of neutrons as a function of angle of incidence have been made for a variety of interfaces, using both an optical model and the Schrödinger equation. The information on the structure of the interfacial region that could be derived from reflectivity profiles is described for the following systems: fatty acid multilayers, black films, the liquid–vapour interface for a one-component system, the solution–vapour interface and the electrode–solution interface. Preliminary experiments have also been done to test the technique using thin films of deuterated stearic acid and copper on glass. 1981-01-01T00:00:00Z http://dspace.bits-pilani.ac.in:8080/jspui/handle/123456789/20712 Title: Triplet State of 5-Nitro-2-furoic acid by Laser Flash Photolysis Spectrum, Lifetime and Reactivity Authors: Kemp, Terence J; Martins, Luis J. A Abstract: Nanosecond laser flash photolysis (347.1 nm) of 5-nitro-2-furoic acid (NFA) in both polar and non-polar solvents at 295 K shows a transient absorption centred at 490 ± 5 nm with εca. 2 × 104 dm3 mol–1 cm–1 which is assigned to the lowest triplet excited state of NFA, denoted 3NFA. While λmax of 3NFA is independent of the solvent polarity, its lifetime is strongly solvent-dependent, being 22.7 ns in water and 274 ns in MeCN. Triplet–triplet energy transfer experiments showed the triplet energy ET to be 240 ± 4 kJ mol–1. 3NFA is extremely reactive, thus it abstracts a hydrogen atom from diphenyl-amine with k2=(8.64 ± 0.44)× 109 dm3 mol–1 s–1 and from diphenylmethanol with k2=(6.94 ± 0.55)× 107 dm3 mol–1 s–1, both in acetone solution. Representative of electron-transfer rates to 3NFA are those of CO2–3 and NNN′ N′-tetramethyl-p-phenylenediamine with k2=(1.56 ± 0.10)× 108 dm3 mol–1 s–1 and k2=(5.98 ± 0.20)′× 109 dm3 mol–1 s–1, respectively. The logarithm of the rate constant of oxidation of a series of electron donors by 3NFA correlates well with the corresponding electrode potentials up to the diffusion limit, although the figure for F– notably fails to fit the plot. The reduction potential of 3NFA is estimated to be 2.17 V. Both the lack of spectral shift with increasing solvent polarity and the reactivity towards hydrogen-atom donors indicate that 3NFA is an nπ* state which retains its nπ* character even in polar solvents. 1981-01-01T00:00:00Z http://dspace.bits-pilani.ac.in:8080/jspui/handle/123456789/20711 Title: Adsorption of Methane + Ethane and Methane +Carbon Monoxide on Molecular Sieves Authors: Veyssiere, Marie-Claude; Clavaud, Christian; Cartraud, Pierre; Cointot, Andre Abstract: Experimental sorption isotherms are obtained for methane, ethane and carbon monoxide in three molecular sieves (two zeolitic and one carbon). Pressures from a few millibar absolute to as high as 30 bar are covered. Sorption isotherms for the binary mixtures methane + ethane and methane + carbon monoxide in the same sorbents are also obtained at 298 K and at equilibrium pressures within the range 2–12 bar. A circulating volumetric apparatus was built and employed for all the binary mixture sorption investigations. Total adsorbed amounts are determined for different gas-phase compositions. Vapour–adsorbate equilibria are determined. A correlation based on I.A.S.T. (Ideal Adsorbed Solution Theory) was studied in order to predict the vapour–adsorbate equilibria. 1981-01-01T00:00:00Z http://dspace.bits-pilani.ac.in:8080/jspui/handle/123456789/20710 Title: Kinetic Studies of Photoinduced Methyl Viologen Reduction with Ruthenium Complexes and Hydrogen Evolution from Water by Hydrogenase Authors: Okura, Ichiro; Kim-Thuan, Nguyen Abstract: Highly active photoinduced systems for methyl viologen reduction have been developed by using ruthenium complexes with long lifetimes in the photoexcited state. The order of activities is as follows: Ru(dime-phen)2+3 > Ru(Cl-phen)2+3 > Ru(phen)2+3 > Ru(bpy)2+3. By kinetic studies the rate constants for quenching the excited ruthenium complexes by methyl viologen have been determined. When hydrogenase was added to the systems containing ruthenium complex, methyl viologen and reducing agent, hydrogen evolution was observed in every system. A higher activity for hydrogen evolution was observed for the system having a higher activity for methyl viologen reduction. 1981-01-01T00:00:00Z