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Spectral studies of a series of complexes of the type [Cu(biL)(PPh,),]+ have been carried out where biL denotes 2,2'-bipyridine, 1,lO-phenanthroline, and 2,9-dimethyl-l,lO-phenanthroline which will be abbreviated as bpy, phen, and dmp, respectively. The dmp complex, unlike the others, emits fairly efficiently in fluid solution and has been studied in detail. All three complexes exhibit metal-to-ligand charge transfer (d-r*) transitions in solution around 360 nm, but solutions of the dmp complex give an extra visible absorption band which is attributable to a second copper complex formed according to the equilibrium: [Cu(dmp)(PPhJ,]+ = [Cu(dmp)]+ + 2PPh3. This dissociation of PPh3 is readily suppressed by the addition of excess PPh,, and under these conditions, the Ellz of the complex is estimated to be 20.7 V vs. SCE. Under the same conditions, the complex has an emission lifetime of 330 ns and an emission quantum yield of 1.4 X lo-'. PPh3 is not a quencher, but both electron-transfer and energy-transfer quenching have been observed. The reduction potential of the excited complex is estimated to be ca. -0.9 V vs. SCE. In rigid glasses at low temperature all three complexes exhibit broad, structureless emissions with lifetimes in the microsecond domain which can be assigned to l d -i~* states. Additional components with lifetimes in the millisecond domain have been observed for the phen and dmp complexes. The latter have characteristic vibronic structures which enable us to assign them as 'r-r* emissions involving the coordinated heterocyclic ligands. The Occurrence of multiple emissions from these systems is rationalized in terms of current models from the literature. Finally, weak sub-nanosecond components have been time resolved from the total emission spectra of the phen and bpy complexes, and possible origins for these components are discussed.

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We report the results from a new pump/probe spectrometer for potential use in combustion diagnostics that employs asynchronous optical sampling. The instrument consists of two frequency-doubled mode-locked Nd:YAG lasers operating at slightly different repetition rates, synchronously pumping two dye lasers (rhodamine 6G) to generate the pump and probe beams. The spectral and temporal capabilities of the instrument are examined by obtaining a spectrum and an excited state decay of rhodamine B. The instrument response is shown to be proportional to pump power, probe power, and sample absorptance. Different frequency synthesizers and different modes of triggering are used to study their effect on signal stability.

We report the first results from a new pump/probe technique called asynchronous optical sampling (ASOPS). The method employs a mode-locked, frequency-doubled Nd:YAG laser operating at a repetition rate of 81.5970000 MHz as the pump laser, and a synchronously pumped dye laser (R6G) operating at a repetition rate of 81.5870000 MHz as the probe laser system. The 10-kHz beat frequency produces a repetitive relative phase walk-out of the pump and probe pulses which replaces the optical delay line used in conventional instruments. Studies of rhodamine B in methanol demonstrate that the instrument response is proportional to pump power, probe power, and sample absorptance. The fluorescence lifetime of 4 × 10−5 M rhodamine B is determined to be 2.3 ns.