The water window is a region of the
electromagnetic spectrum
The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies.
The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from ...
in which
water
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...
is transparent to
soft x-ray
X-rays (or rarely, ''X-radiation'') are a form of high-energy electromagnetic radiation. In many languages, it is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it in 1895 and named it ' ...
s. 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 molecule
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...
s) is absorbing. These wavelengths could be used in an
x-ray microscope
An X-ray microscope uses electromagnetic radiation in the soft X-ray band to produce magnified images of objects. Since X-rays penetrate most objects, there is no need to specially prepare them for X-ray microscopy observations.
Unlike visible li ...
for viewing living specimens.
References
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{{X-ray science
X-rays