The water window is a region of the electromagnetic spectrum in which water is transparent to soft x-rays. The window extends from the K-absorption edge of carbon at 282 eV (68 PHz, 4.40 nm wavelength) to the K-edge of oxygen at 533 eV (129 PHz, 2.33 nm wavelength). Water is transparent to these X-rays, but carbon and its organic compounds are absorbing. These wavelengths could be used in an x-ray microscope for viewing living specimens.12 This is technically challenging because few if any viable lens materials are available above extreme ultraviolet.
References
References
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- Spielmann, C.; Burnett, N. H.; Sartania, S.; Koppitsch, R.; Schnürer, M.; Kan, C.; Lenzner, M.; Wobrauschek, P.; Krausz, F. (24 Oct 1997). "Generation of Coherent X-rays in the Water Window Using 5-Femtosecond Laser Pulses". Science. 278 (5338): 661–664. Bibcode:1997Sci...278..661S. doi:10.1126/science.278.5338.661.
- Sebastian Wachsmann-Hogiu; Alexander J Annala; Daniel L Farkas (2004). Colin E. Webb and Julian D. C. Jones (ed.). Handbook of Laser Technology and Applications: Applications. IOP Publishing. p. 2138. ISBN 978-0-7503-0966-0.