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An excited-state solute—solvent complex (exciplex) has been shown to be responsible for a large red shift and loss of vibrational structure in the fluorescence spectra of indole and indole derivatives in polar solvents. Solute—solvent stoichiometry of 1:2 and 1:1 is observed with associating and nonassociating solvents, respectively. Hydrogen bonding between the indole >N–H group and solvent is shown not to be responsible for the interaction. It is suggested that the exciplex state is a charge-transfer state and is an intermediate in the process of electron transfer from the solute to the solvent.

Low-temperature superconductors containing artificial pinning centers (APC) have produced record critical current densities in NbTi at magnetic fields below 4 T and promise further improvements at these and higher fields. Peak current densities are achieved when pinning center spacings are matched to spacings of the flux line lattice at the field of operation. The enhancement of Jc through inclusion of artificial pinning materials is accompanied by reduction in Tc and Hc2 through proximity effects. We find that the choice of the superconducting alloy as well as the pin material has marked effect on both the characteristic pinning force Fp and the critical magnetic field Hc2.

Rate constants for both radiative and non-radiative relaxation of the fluorescent state of indole and several methyl-indoles in solution have been calculated from fluorescence lifetime and quantum yield values.Radiative relaxation for indoles is solvent dependent while non-radiative relaxation is attributed to at least two processes, one of which is both solvent and temperature dependent. The latter process measured in aqueous solvents manifests a pattern of compensation of activation enthalpy by activation entropy with an isokinetic temperature for indole of 283°K.A quantitatively consistent description of the excited-state behavior of 1-Me-indole in both free and exciplex state is provided. Small deviations in fluorescence parameters for indole suggest a more complicated set of events.