Optically detected zero field magnetic resonance studies of the photoexcited triplet states of chlorophyll a and b

Abstract

The zero‐field EPR transitions for the triplet states of chlorophyll a and chlorophyll b in n‐octane solutions at 2°K have been observed by optical detection methods. Both triplet absorption detection of magnetic resonance and fluorescence‐microwave double resonance techniques were used. Sharp‐line (5–20 MHz) zero‐field EPR spectra were recorded for both molecules. The rates of depopulation for the individual triplet state spin sublevels were determined by microwave‐modulated fluorescence intensity measurements. These experiments show that the middle spin sublevel is the most active in triplet state intersystem crossing for both chlorophyll a and chlorophyll b.