Intersystem Crossing Relative Rates from Pulsed-Excitation Phosphorescence Microwave Double Resonance.

摘要

A new phosphorescence microwave double resonance technique is described from which the ratios of the intersystem crossing (ISC) rates to the different zero-field (zf) levels can be determined. After short pulsed singlet-singlet excitation and at times short compared to the decay times of the different zf levels of T(1) (by spin lattice relaxation (SLR) or T(1) to S(0) unimolecular decay),the ratios of the ISC rates are equal to the ratios of the zf level populations. The latter can be determined from the observed changes in the phosphorescence intensity upon fast sweeping (or short-pulsing) of microwaves capable of saturating or inverting the populations of the zf levels. The method is demonstrated at 1.4K where the SLR is slow and the stringent requirements set upon the excitation and microwave pulse widths and the short delay times are eliminated. (Author)