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Direct imaging of active orbitals in quantum materials

In quantum materials based on transition metals, rare-earth and actinide elements, electronic states are characterized by electrons in orbitals d and f, combined with the solid's strong band formation. Until now, to estimate ...

CubeSats prove their worth for scientific missions

Only a few years ago, the astronomy and heliophysics communities were skeptical about whether CubeSats could reliably obtain scientific data. But these breadloaf-size satellites have proven their ability to return useful ...

Catching fast changes in excited molecules

It's hard to see certain molecules react. The reaction is just that fast. Until now. A team of scientists devised a way to reveal time- and energy-resolved information on "dark" states of molecules—ones that are normally ...

Life could be evolving right now on nearest exoplanets

Excitement about exoplanets skyrocketed when rocky Earth-like planets were discovered orbiting in the habitable zone of some of our closest stars – until hopes for life were dashed by the high levels of radiation bombarding ...

Two-armed 3-D printing

Twin robotic arms work together as part of a project to construct what will be the largest, most complex object ever 3-D printed in titanium: a test version of the 3-m diameter 'optic bench' at the heart of ESA's Athena X-ray ...

Where space missions are born

A high-resolution radar mission to Earth's 'evil twin' Venus, a spacecraft to detect the most powerful explosions in the Universe and an observatory for the cool, dusty cosmos to investigate the origins of stars: ESA's Concurrent ...

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X-radiation (composed of X-rays) is a form of electromagnetic radiation. X-rays have a wavelength in the range of 10 to 0.01 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz (3 × 1016 Hz to 3 × 1019 Hz) and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays. In many languages, X-radiation is called Röntgen radiation after Wilhelm Conrad Röntgen, who is generally credited as their discoverer, and who had called them X-rays to signify an unknown type of radiation.:1-2

X-rays are primarily used for diagnostic radiography and crystallography. As a result, the term X-ray is metonymically used to refer to a radiographic image produced using this method, in addition to the method itself. X-rays are a form of ionizing radiation and as such can be dangerous.

X-rays from about 0.12 to 12 keV are classified as soft X-rays, and from about 12 to 120 keV as hard X-rays, due to their penetrating abilities.

The distinction between X-rays and gamma rays has changed in recent decades. Originally, the electromagnetic radiation emitted by X-ray tubes had a longer wavelength than the radiation emitted by radioactive nuclei (gamma rays). So older literature distinguished between X- and gamma radiation on the basis of wavelength, with radiation shorter than some arbitrary wavelength, such as 10−11 m, defined as gamma rays. However, as shorter wavelength continuous spectrum "X-ray" sources such as linear accelerators and longer wavelength "gamma ray" emitters were discovered, the wavelength bands largely overlapped. The two types of radiation are now usually defined by their origin: X-rays are emitted by electrons outside the nucleus, while gamma rays are emitted by the nucleus.

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