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Extreme ultraviolet
Extreme ultraviolet radiation (EUV or XUV) or high-energy ultraviolet radiation is electromagnetic radiation in the part of the electromagnetic spectrum spanning wavelengths shorter than the hydrogen Lyman-alpha line from 121 nm down to the X-ray band of 10 nm. By the Planck–Einstein equation the EUV photons have energies from 10.26 eV up to 124.24 eV where we enter the X-ray energies. EUV is naturally generated by the solar corona and artificially by plasma, high harmonic generation sources and synchrotron light sources. Since the ultraviolet C range extends to 100 nm, there is some overlap in the terms.
The main uses of extreme ultraviolet radiation are photoelectron spectroscopy, solar imaging, and lithography. In air, EUV is the most highly absorbed component of the electromagnetic spectrum, requiring high vacuum for transmission.
Neutral atoms or condensed matter do not have large enough energy transitions to emit EUV radiation. Ionization must take place first. EUV light can only be emitted by electrons which are bound to multicharged positive ions; for example, to remove an electron from a +3 charged carbon ion (three electrons already removed) requires about 65 eV. Such electrons are more tightly bound than typical valence electrons. The existence of multicharged positive ions is only possible in a hot dense plasma. Alternatively, the free electrons and ions may be generated temporarily and instantaneously by the intense electric field of a very-high-harmonic laser beam. The electrons accelerate as they return to the parent ion, releasing higher energy photons at diminished intensities, which may be in the EUV range. If the released photons constitute ionizing radiation, they will also ionize the atoms of the harmonic-generating medium, depleting the sources of higher-harmonic generation. The freed electrons escape since the electric field of the EUV light is not intense enough to drive the electrons to higher harmonics, while the parent ions are no longer as easily ionized as the originally neutral atoms. Hence, the processes of EUV generation and absorption (ionization) strongly compete against each other.
In the beginning of the 21st century multiple EUV sources appeared based on the free-electron laser and table top EUV sources based on high harmonic generation techniques. First generation commercial systems for EUV lithography based on laser-produced plasma (LPP) light generation have been shipped.
EUV light can also be emitted by free electrons orbiting a synchrotron.
Continuously tunable narrowband EUV light can be generated by four wave mixing in gas cells of krypton and hydrogen to wavelengths as low as 110 nm. In windowless gas chambers fixed four wave mixing has been seen as low as 75 nm.
When an EUV photon is absorbed, photoelectrons and secondary electrons are generated by ionization, much like what happens when X-rays or electron beams are absorbed by matter.
The response of matter to EUV radiation can be captured in the following equations:
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Extreme ultraviolet AI simulator
(@Extreme ultraviolet_simulator)
Extreme ultraviolet
Extreme ultraviolet radiation (EUV or XUV) or high-energy ultraviolet radiation is electromagnetic radiation in the part of the electromagnetic spectrum spanning wavelengths shorter than the hydrogen Lyman-alpha line from 121 nm down to the X-ray band of 10 nm. By the Planck–Einstein equation the EUV photons have energies from 10.26 eV up to 124.24 eV where we enter the X-ray energies. EUV is naturally generated by the solar corona and artificially by plasma, high harmonic generation sources and synchrotron light sources. Since the ultraviolet C range extends to 100 nm, there is some overlap in the terms.
The main uses of extreme ultraviolet radiation are photoelectron spectroscopy, solar imaging, and lithography. In air, EUV is the most highly absorbed component of the electromagnetic spectrum, requiring high vacuum for transmission.
Neutral atoms or condensed matter do not have large enough energy transitions to emit EUV radiation. Ionization must take place first. EUV light can only be emitted by electrons which are bound to multicharged positive ions; for example, to remove an electron from a +3 charged carbon ion (three electrons already removed) requires about 65 eV. Such electrons are more tightly bound than typical valence electrons. The existence of multicharged positive ions is only possible in a hot dense plasma. Alternatively, the free electrons and ions may be generated temporarily and instantaneously by the intense electric field of a very-high-harmonic laser beam. The electrons accelerate as they return to the parent ion, releasing higher energy photons at diminished intensities, which may be in the EUV range. If the released photons constitute ionizing radiation, they will also ionize the atoms of the harmonic-generating medium, depleting the sources of higher-harmonic generation. The freed electrons escape since the electric field of the EUV light is not intense enough to drive the electrons to higher harmonics, while the parent ions are no longer as easily ionized as the originally neutral atoms. Hence, the processes of EUV generation and absorption (ionization) strongly compete against each other.
In the beginning of the 21st century multiple EUV sources appeared based on the free-electron laser and table top EUV sources based on high harmonic generation techniques. First generation commercial systems for EUV lithography based on laser-produced plasma (LPP) light generation have been shipped.
EUV light can also be emitted by free electrons orbiting a synchrotron.
Continuously tunable narrowband EUV light can be generated by four wave mixing in gas cells of krypton and hydrogen to wavelengths as low as 110 nm. In windowless gas chambers fixed four wave mixing has been seen as low as 75 nm.
When an EUV photon is absorbed, photoelectrons and secondary electrons are generated by ionization, much like what happens when X-rays or electron beams are absorbed by matter.
The response of matter to EUV radiation can be captured in the following equations: