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The picosecond transient Raman spectra of S 1 trans-4,4 -diphenylstilbene (DPS) in benzene and toluene at an excitation wavelength of 310 nm and probe wavelengths of 630 and 660 nm are presented. No significant dynamic variations between benzene and toluene in the change in peak position of vibrational modes in S 1 DPS with delay were observed. These data indicate that vibrational relaxation occurs at similar rates in both solvents. The vibrational relaxation dynamics of S 1 DPS in the aromatic solvents were also compared with those in dioxane and methylene chloride. It is suggested that specific solute-solvent effects contribute to vibrational relaxation in these solvents. It was found that the relative intensities of Raman bands that contain contributions from the phenyl-phenyl stretch are different for S 1 DPS in toluene compared with S 1 DPS in benzene. The difference in relative intensities is attributed to an equilibrium conformation in S 1 DPS that is perturbed by the methyl group on toluene, giving rise to a variation in the conformation of the biphenyl group in S 1 DPS.

A standard four-tier design template may have been followed for most countries and raises the possibility that simpler and more tailored designs may be warranted.