Effect of hydrogen bonding on far-ultraviolet water absorption and potential implications for 193-nm ArF excimer laser-tissue interaction

Joseph T. Walsh Jr.; Paul T. Staveteig

doi:10.1117/12.209880

22 May 1995 Effect of hydrogen bonding on far-ultraviolet water absorption and potential implications for 193-nm ArF excimer laser-tissue interaction

Joseph T. Walsh Jr., Paul T. Staveteig

Author Affiliations +

Proceedings Volume 2391, Laser-Tissue Interaction VI; (1995) https://doi.org/10.1117/12.209880
Event: Photonics West '95, 1995, San Jose, CA, United States

Abstract

The mechanisms causing transient 193-nm optical absorption of collagen during ablative-fluence ArF excimer pulses are poorly understood. The preponderance of hypotheses proposed to explain this phenomenon, such as ultrafast secondary-structure denaturation of proteins and transient free radical formation, focus on the protein matrix and ignore potential contributions from other tissue components such as water. A substantial body of spectroscopic literature places 193 nm adjacent to a steep absorption edge of water that rises to 60,000 cm^-1 at 163 nm; other evidence shows that this absorption edge shifts toward 193 nm upon hydrogen-bond breakage. In this paper we show that heating of water from 20-100°C increases the liquid's absorption coefficient. Further investigations using an infrared pump laser show a significant increase in absorption by water of a 193-nm probe beam. Based on this evidence, we speculate that 193-nm laser ablation of tissue may contain a photothermal component related to dynamic absorption of incident radiation by water.

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Joseph T. Walsh Jr. and Paul T. Staveteig "Effect of hydrogen bonding on far-ultraviolet water absorption and potential implications for 193-nm ArF excimer laser-tissue interaction", Proc. SPIE 2391, Laser-Tissue Interaction VI, (22 May 1995); https://doi.org/10.1117/12.209880

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