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Fiber-Optic System for 77 K Phosphorescence Lifetime Measurements of Polycylic Aromatic Compounds in Shpolskii Matrices
Volume 55, Number 9 (Sept. 2001) Page 1266-1272
Martin, Travis L.; Campiglia, Andres D.
A fiber-optic system is reported for rapid, accurate, and precise 77 K measurements of relatively long phosphorescence lifetimes (τp = 200 ms). The instrument employs stimulated Raman scattering in connection with a pulsed laser source for sample excitation. Phosphorescence decay waveforms are collected at maximum emission wavelengths with a single channel detection system and the aid of a LabVIEW based in-house program acting as a data acquisition instrument, data storage device, and data interpreter. By means of program looping, up to 20 decays are recorded from a frozen sample in less than 5 min. A cryogenic fiber-optic probe directly frozen into the sample matrix removes the random errors associated with the classic sample freezing procedure and provides excellent reproducibility of measurements. The relative standard deviations of τp measured from several polycyclic aromatic compounds varied between 0 and 4.30%. The simplicity of the experimental procedure, the rather large τp differences observed from compounds within the same pollutant class, and the analytical figures of merit provide a solid foundation for pursuing low-temperature phosphorescence, time-resolved low-temperature phosphorescence, and low-temperature multidimensional luminescence analysis.