Water window

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 thus, organic molecules) is absorbing. These wavelengths could be used in an x-ray microscope for viewing living specimens.[1][2]

References

1. De Stasio, G.; Gilbert, B.; Nelson, T.; Hansen, R.; Wallace, J.; Mercanti, D.; Capozi, M.; Baudat, P. A.; Perfetti, P.; Margaritondo, G.; Tonner, B. P. (January 2000). "Feasibility tests of transmission x-ray photoelectron emission microscopy of wet samples" (PDF). Review of Scientific Instruments. 71: 11–14. Bibcode:2000RScI...71...11D. doi:10.1063/1.1150151. Archived from the original (PDF) on 2017-08-13.
2. 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.