Molecular Phosphorescence Research Articles

Comparison of Pulsed Source with Continuous Wave Source Excitation in Atomic and Molecular Luminescence Spectrometry via Signal/Noise Ratio Calculations

Pulsed source excitation-gated detection (with or without time resolution) and cw excitation-cw detection are compared theoretically with respect to signal/noise (S/N) ratios in atomic and molecular luminescence spectrometry. The calculations indicate that in those cases where there is no loss in flux due to pulsing, pulsed source excitation with delayed gated detection results in a considerable improvement in S/N as long as the major noise sources are either not related to the source decay or, if related to the source decay or luminescence decay of impurities, the delay time between excitation and detection is greater than the corresponding source or impurity decay times. In general, pulsed source excitation-gated detection and modulated source lock-in detection do not provide significant S/N advantages over cw excitation and cw detection unless the major source of noise is related to either the detector or to non-source-induced background. Calculations of S/N ratio are given for a variety of analytically useful situations in atomic fluorescence spectrometry, molecular fluorescence spectrometry of gas phase and condensed phase species, and molecular phosphorescence spectrometry.

Ternary Lanthanide Complexes of the Type M(Hsal)3(TPX → O)2 and a Fluorescence Spectral Study of the Eu(III) Analogue

Ternary lanthanide complexes of the general formula M(Hsal)3 (TPX→O)2 , where M = lanthanide (III) ion, Hsal=salicylate ion =C6H4(OH)COO- and X = P or As have been isolated as solids from the benzene phase during liquid-liquid extraction studies of M(Hsal)3 complexes with benzene solutions of TPX→O. The coordinated nature of the TPX→O ligands has been established from the observed shifts of the X → O frequency in the infrared. A lowering of the 1190 cm-1 P → O frequency where X = P , and an increase in the 885 cm-1 As → O frequency where X = As have been observed for the ternary complexes. The infrared spectra of the ternary complexes in general indicate the coordinated nature of the salicylate ions. The luminescence spectra of Eu(Hsal)3 (TPPO)2 and Eu(Hsal)3 (TPAsO)2 complexes have also been investigated at 77 °K. Beside the emission of the characteristic red europium fluorescence due to the excitation of the complexes with near UV light, emission of a blue molecular phosphorescence from the complexes has also been observed. The fluorescence intensities of the f → f transitions are, however, weak. This point has been discussed.

New spectroscopic techniques for studying the origin of molecular phosphorescence

At temperature for which the electron spin-lattice relaxation times between the zero-field levels of the lowest triplet state are comparable to or longer than the phosphorescence lifetimes, the relative intensity of the different vibronic bands in the phosphorescence spectrum and the observed decays are sensitive to changes in temperature, application of magnetic fields, and saturation of the triplet state zero-field transitions with microwave radiation. From the changes in the spectrum and in the decays upon applying these perturbations, the zero-field level(s) responsible for the intensity of each vibronic band can be determined, as well as the complete description of the spin-orbit coupling scheme.