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Proceedings Paper

Determination of the absolute two-photon absorption cross section of tryptophan
Author(s): Parijat Sengupta; J. Balaji; S. Mukherjee; R. Philip; G. Ravindra Kumar; Sudipta Maiti
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Paper Abstract

Two-photon excitation can excite physiological ultraviolet (UV) chromophores at visible wavelengths and holds significance for applications such as non-linear microscopy, micro-pharmacology, localized heating and tissue ablation. However, little quantitative data is available on the absolute two-photon absorption cross sections ((sigma) 2) of these molecules. Their low two-photon absorbance and limited solubility implies that the sensitivity required for such measurements is much higher than that available from standard techniques. We employ the recently developed generalized z-scan technique to measure the absolute value of the (sigma) 2 of tryptophan, the most ubiquitous of the physiological near-UV chromophores, and obtain the value of 32.0 +/- 1.2 mGM (1 GM equals 10-50 cm4sec/photon/molecule) at 532 nm. This is the first determination of the absolute (sigma) 2 of any biological UV chromophore, and can be used to calibrate the previously reported relative two-photon excitation spectra of a number of such molecules.

Paper Details

Date Published: 24 April 2001
PDF: 4 pages
Proc. SPIE 4262, Multiphoton Microscopy in the Biomedical Sciences, (24 April 2001); doi: 10.1117/12.424573
Show Author Affiliations
Parijat Sengupta, Tata Institute of Fundamental Research (India)
J. Balaji, Tata Institute of Fundamental Research (India)
S. Mukherjee, Tata Institute of Fundamental Research (India)
R. Philip, Tata Institute of Fundamental Research (India)
G. Ravindra Kumar, Tata Institute of Fundamental Research (India)
Sudipta Maiti, Tata Institute of Fundamental Research (India)


Published in SPIE Proceedings Vol. 4262:
Multiphoton Microscopy in the Biomedical Sciences
Ammasi Periasamy; Peter T. C. So, Editor(s)

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