水窗

水窗是指波長範圍處在2.34nm與4.4nm之間的軟X射線。前者對應氧原子的K吸收帶，後者對應碳原子的K吸收帶，即光子能量範圍在530eV到280eV間的X射線。在此範圍內，水不吸收X射線，即水對X射線是透明的。但是，此範圍內的X射線會被氮原子和其他構成生物機體的元素吸收，因此，該波長可用於對活體生物樣本進行X射線顯微^[1]^[2]．

參考資料

^ Gelsomina De Stasio, B. Gilbert, T. Nelson, R. Hansen, J. Wallace, D. Mercanti, M. Capozi, P. A. Baudat, P. Perfetti, G. Margaritondo, B. P. Tonner. Feasibility tests of transmission x-ray photoelectron emission microscopy of wet samples. Review of Scientific Instruments: 11–14. [2018-04-02]. doi:10.1063/1.1150151. （原始內容存檔於2020-08-09）.
^ Ch Spielmann, N. H. Burnett, S. Sartania, R. Koppitsch, M. Schnürer, C. Kan, M. Lenzner, P. Wobrauschek, F. Krausz. Generation of Coherent X-rays in the Water Window Using 5-Femtosecond Laser Pulses. Science. 1997-10-24, 278 (5338): 661–664 [2018-04-02]. ISSN 0036-8075. doi:10.1126/science.278.5338.661. （原始內容存檔於2018-01-01）（英語）.

Sebastian Wachsmann-Hogiu; Alexander J Annala and Daniel L Farkas. Colin E. Webb and Julian D. C. Jones , 編. Handbook of Laser Technology and Applications: Applications. IOP Publishing. 2004: 2138. ISBN 978-0-7503-0966-0.

[1] Gelsomina De Stasio, B. Gilbert, T. Nelson, R. Hansen, J. Wallace, D. Mercanti, M. Capozi, P. A. Baudat, P. Perfetti, G. Margaritondo, B. P. Tonner. Feasibility tests of transmission x-ray photoelectron emission microscopy of wet samples. Review of Scientific Instruments: 11–14. [2018-04-02]. doi:10.1063/1.1150151. （原始內容存檔於2020-08-09）.

[2] Ch Spielmann, N. H. Burnett, S. Sartania, R. Koppitsch, M. Schnürer, C. Kan, M. Lenzner, P. Wobrauschek, F. Krausz. Generation of Coherent X-rays in the Water Window Using 5-Femtosecond Laser Pulses. Science. 1997-10-24, 278 (5338): 661–664 [2018-04-02]. ISSN 0036-8075. doi:10.1126/science.278.5338.661. （原始內容存檔於2018-01-01）（英語）.

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