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Published June 1976 | Published
Journal Article Open

Responses of Phycomyces indicating optical excitation of the lowest triplet state of riboflavin


Phototropic and light growth responses of the sporangiophore of Phycomyces have been elicited using tunable laser stimulation from 575 to 630 nm. The growth response shows additional components of the action spectrum with a sharp peak at 595 nm, a sharp cut-off at 585 nm, and a tail extending beyond 630 nm. The integral over the electronic transition (f-value) is 1.5 x 10^-9 times that at 455 nm. These parameters indicate a direct transition from the ground state to the lowest triplet state of riboflavin.

Additional Information

© 1976 by the National Academy of Sciences. Contributed by Max Delbrück, March 15, 1976. The experiments were performed in the laboratory of Prof. A. Yariv of the Electrical Engineering Department of the California Institute of Technology. The authors wish to express their appreciation to Professor Yariv for putting the laser facilities at their disposal, and to Messrs P. Agmon, D. Armstrong, and H.W. Yen for indefatigable help with laser troubleshooting. The work was supported by National Science Foundation Grant no. BMS 75-11316.

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