Coherent stimulated light emission (lasing) in covalently linked chlorophyll dimers

Journal Article · Mon May 01 00:00:00 EDT 1978 · Proc. Natl. Acad. Sci. U.S.A.; (United States)

DOI:https://doi.org/10.1073/pnas.75.5.2076· OSTI ID:6952487

Hindman, J C; Kugel, R; Wasielewski, M R; Katz, J J

The covalently linked chlorophyll a dimer exhibits remarkably different properties in the folded and open configurations. In the folded configuration the absorption maximum is at 695 nm and the fluorescence maximum is at 730 nm. Laser output at 733 and 735 nm is obtained for solutions in wet benzene and 0.1 M ethanol/toluene, respectively. Measurements of fluorescence lineshapes, made with a transverse excited atmospheric (TEA) nitrogen laser for excitation, show the lifetime shortening associated with stimulated emission resulting from appreciable concentrations of molecules in S/sub 1/ excited states. In contrast, the open dimer has absorption and fluorescence spectra essentially the same as those of chlorophyll a monomer. Unlike either the folded dimer or chlorophyll a monomer, the open dimer shows no laser emission or fluorescence lifetime shortening. It does not appear that the behavior of the open dimer can be explained in terms of excimer or triplet formation or by nonradiative decay processes. It is suggested that absorption of the exciting radiation by S/sub 1/, leading to the formation of an exciplex or charge transfer state, may be involved. Significantly, no large changes in fluorescence quantum yield or fluorescence lifetime are observed for these dimers as compared to monomer chlorophyll. This suggests that concentration quenching and lifetime shortening in condensed chlorophyll systems involve more than the simple proximity of two chlorophyll molecules.

• Research Organization: Argonne National Lab., IL
• OSTI ID: 6952487
• Journal Information: Proc. Natl. Acad. Sci. U.S.A.; (United States), Vol. 75:5
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CHLOROPHYLL
BIOCHEMICAL REACTION KINETICS
FLUORESCENCE
MEASURING METHODS
LASERS
DIMERS
QUENCHING
CARBOXYLIC ACIDS
HEAT TREATMENTS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
KINETICS
LUMINESCENCE
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHYTOCHROMES
PIGMENTS
PORPHYRINS
REACTION KINETICS
550200* - Biochemistry