Unique Luminescences of Dry Chlorophylls

Abstract

Dry chlorophylls a and b in a rigid glass hydrocarbon solvent have intense emission at 7550 A and 7330 A, respectively. In each case, the room temperature absorption spectra show the presence of a band shoulder on the long wavelength side of the main red band. Both the emission and the absorption bands disappear in the presence of hydroxyllic solvents. The absorption and emission are interpreted as n-π* singlet and n-π* triplet transitions, respectively. The lifetime of the n-π* triplet emission in chlorophyll a is estimated to be 10—3 second. Cu chlorophyll b has an intense phosphorescence at 8740 A with a lifetime of less than 10—4 second. The differences in the room temperature emission spectra for chlorophylls a and b are discussed.