Two-photon excitation of 4'-hydroxymethyl-4,5',8-trimethylpsoralen.

Abstract

Psoralens are a class of pharmaceutical agents commonly used to treat several cutaneous disorders. When irradiated with a mode-locked titanium: sapphire (Ti:sapphire) laser tuned to 730 nm, an aqueous solution of 4'-hydroxymethyl-4,5',8-trimethylpsoralen (HMT) emits blue light. The emission spectrum is centered at 452 nm and is identical to that obtained by one-photon excitation with UVA excitation, and its magnitude depends quadratically on the intensity of laser excitation. These results suggest that two-photon excitation occurs to a potentially photochemically active state. To estimate the two-photon absorption cross section, it was first necessary to measure the emission quantum yield of HMT using 365 nm excitation at room temperature that resulted in a value of 0.045 +/- 0.007. The two-photon absorption cross section of HMT at 730 nm is therefore estimated to be 20 x 10(-50) cm4 s (20 Göppert-Mayer). The excited-state photophysics and photochemistry of psoralens suggest potential applications to cutaneous phototherapy in diseases such as psoriasis and dystrophic epidermolysis bullosa.

• Authors: D H Oh, R J Stanley, M Lin, W K Hoeffler, S G Boxer, M W Berns, E A Bauer
• Journal: Photochemistry and photobiology (Photochem Photobiol) Vol. 65 Issue 1 Pg. 91-5 (Jan 1997) ISSN: 0031-8655 [Print] United States
• PMID: 9066288 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S., Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Rhodamines
• hydroxymethyltrioxsalen
• rhodamine B
• Aluminum Oxide
• Trioxsalen

Topics

• Aluminum Oxide
• Lasers
• Rhodamines
• Spectrophotometry, Atomic
• Trioxsalen (analogs & derivatives, chemistry)