Editing Ultraviolet (section)

==Subtypes==

The [[electromagnetic spectrum]] of ultraviolet radiation (UVR), defined most broadly as 10–400&nbsp;nanometers, can be subdivided into a number of ranges recommended by the [[ISO standard]] ISO 21348:<ref>
{{cite web
 | title = ISO 21348 Definitions of Solar Irradiance Spectral Categories
 | website = Space Weather (spacewx.com)
 | url = http://www.spacewx.com/pdf/SET_21348_2004.pdf
 | url-status = dead  | access-date = 25 August 2013
 | archive-url = https://web.archive.org/web/20131029233428/http://www.spacewx.com/pdf/SET_21348_2004.pdf
 | archive-date = 29 October 2013
}}
</ref>

{| class="wikitable" style="margin:2em auto; text-align:center;"
|-
!colspan=2| Name
!rowspan=2| [[Photon energy]] ([[electronvolt|eV]],&nbsp;[[attojoule#Multiples|aJ]])
!rowspan=2| Notes/alternative names
|-
! Abbreviation
! [[Wavelength]] (nm)
|-
| colspan=4 style="background:lightgrey" |
|-
|colspan=2| Ultraviolet A
|rowspan=2| {{convert|3.10|–|3.94|eV|aJ|abbr=values|disp=br}}
|rowspan=2 style="text-align:left;" | Long-wave&nbsp;UV, [[blacklight]], not absorbed by the [[ozone layer]]: soft&nbsp;UV.
|-
| UVA <!-- no hyphen per ISO ref -->
| 315–400
|-
|colspan=2| Ultraviolet B
|rowspan=2| {{convert|3.94|–|4.43|eV|aJ|abbr=values|disp=br}}
|rowspan=2 style="text-align:left;" | Medium-wave&nbsp;UV, mostly absorbed by the ozone layer: intermediate&nbsp;UV; [[Carl Dorno|Dorno]] radiation.
|-
| UVB
| 280–315
|-
|colspan=2| Ultraviolet C
|rowspan=2| {{convert|4.43|–|12.4|eV|aJ|abbr=values|disp=br}}
|rowspan=2 style="text-align:left;" | Short-wave&nbsp;UV, [[ultraviolet germicidal irradiation|germicidal]]&nbsp;UV, [[ionizing radiation]] at shorter wavelengths, completely absorbed by the ozone layer and atmosphere: hard&nbsp;UV.
|-
| UVC
| 100–280
|-
| colspan=4 style="background:lightgrey" |
|-
|colspan=2| Near ultraviolet
|rowspan=2| {{convert|3.10|–|4.13|eV|aJ|abbr=values|disp=br}}
|rowspan=2 style="text-align:left;" | Visible to birds, insects, and fish.
|-
| NUV <!-- no hyphen per ISO ref -->
| 300–400
|-
|colspan=2| Middle ultraviolet
|rowspan=2| {{convert|4.13|–|6.20|eV|aJ|abbr=values|disp=br}}
|rowspan=2 style="text-align:left;" |
|-
| MUV
| 200–300
|-
|colspan=2| Far ultraviolet
|rowspan=2| {{convert|6.20|–|10.16|eV|aJ|abbr=values|disp=br}}
|rowspan=2 style="text-align:left;" | [[Ionizing radiation]] at shorter wavelengths.
|-
| FUV
| ''122–200''
|-
|colspan=2| Hydrogen<br />[[Lyman-alpha]]
|rowspan=2| {{convert|10.16|–|10.25|eV|aJ|abbr=values|disp=br}}
|rowspan=2 style="text-align:left;" | Spectral line at 121.6&nbsp;nm, 10.20&nbsp;eV.
|-
| H&nbsp;Lyman‑α
| 121–122
|-
|colspan=2| [[Extreme ultraviolet]]
|rowspan=2| {{nobr|{{convert|10.25|–|124|eV|aJ|abbr=values|disp=br}}}}
|rowspan=2 style="text-align:left;" | Entirely [[ionizing radiation]] by some definitions; completely absorbed by the atmosphere.
|-
| EUV <!-- no hyphen per ISO ref -->
| 10–121 <!-- 10nm is 124eV -->
|-
| colspan=4 style="background:lightgrey" |
|-
|colspan=2| [[Far-UVC]]
|rowspan=2| {{convert|5.28|–|6.20|eV|aJ|abbr=values|disp=br}}
|rowspan=2 style="text-align:left;" | Germicidal but strongly absorbed by outer skin layers, so does not reach living tissue.
|-
|
| 200–235 <!-- Just above the VUV range -->
|-
|colspan=2| Vacuum ultraviolet
|rowspan=2| {{nobr|{{convert|6.20|–|124|eV|aJ|abbr=values|disp=br}}}}
|rowspan=2 style="text-align:left;" | Strongly absorbed by atmospheric oxygen, though 150–200&nbsp;nm wavelengths can propagate through nitrogen.
|-
| VUV <!-- no hyphen per ISO ref -->
| 10–200 <!-- 10nm is 124eV -->
|}

Several solid-state and vacuum devices have been explored for use in different parts of the UV spectrum. Many approaches seek to adapt visible light-sensing devices, but these can suffer from unwanted response to visible light and various instabilities. Ultraviolet can be detected by suitable [[photodiode]]s and [[photocathode]]s, which can be tailored to be sensitive to different parts of the UV spectrum. Sensitive UV [[photomultiplier]]s are available. [[Spectrometer]]s and [[radiometer]]s are made for measurement of UV radiation. Silicon detectors are used across the spectrum.<ref>
{{cite journal
 |last1=Gullikson  |first1=E.M.      |last2=Korde  |first2=R.
 |last3=Canfield   |first3=L.R.      |last4=Vest   |first4=R.E.
 |year=1996
 |title=Stable silicon photodiodes for absolute intensity measurements in the VUV and soft X-ray regions
 |journal=Journal of Electron Spectroscopy and Related Phenomena
 |volume=80  |pages=313–316
 |doi=10.1016/0368-2048(96)02983-0
 |bibcode=1996JESRP..80..313G |url=http://ts.nist.gov/MeasurementServices/Calibrations/upload/JES-80.PDF
 |access-date=2011-11-08
 |archive-url=https://web.archive.org/web/20090109215922/http://ts.nist.gov/MeasurementServices/Calibrations/upload/JES-80.PDF
 |archive-date=2009-01-09
}}
</ref>

Vacuum UV, or VUV, wavelengths (shorter than 200&nbsp;nm) are strongly absorbed by molecular [[oxygen]] in the air, though the longer wavelengths around 150–200&nbsp;nm can propagate through [[nitrogen]]. Scientific instruments can, therefore, use this spectral range by operating in an oxygen-free atmosphere (pure nitrogen, or [[argon]] for shorter wavelengths), without the need for costly vacuum chambers. Significant examples include 193-nm [[photolithography]] equipment (for [[semiconductor manufacturing]]) and [[circular dichroism]] spectrometers.<ref>{{Cite web |title=Circular Dichroism Spectroscopy |url=https://jascoinc.com/learning-center/theory/spectroscopy/circular-dichroism-spectroscopy/ |access-date=2025-01-21 |website=JASCO Inc. |language=en-US}}</ref>

Technology for VUV instrumentation was largely driven by solar astronomy for many decades. While optics can be used to remove unwanted visible light that contaminates the VUV, in general, detectors can be limited by their response to non-VUV radiation, and the development of [[Solar-blind technology|solar-blind devices]] has been an important area of research. Wide-gap solid-state devices or vacuum devices with high-cutoff photocathodes can be attractive compared to silicon diodes.

Extreme UV (EUV or sometimes XUV) is characterized by a transition in the physics of interaction with matter. Wavelengths longer than about 30&nbsp;nm interact mainly with the outer [[valence electron]]s of atoms, while wavelengths shorter than that interact mainly with inner-shell electrons and nuclei. The long end of the EUV spectrum is set by a prominent He<sup>+</sup> spectral line at 30.4&nbsp;nm. EUV is strongly absorbed by most known materials, but synthesizing [[multilayer optics]] that reflect up to about 50% of EUV radiation at [[normal incidence]] is possible. This technology was pioneered by the [[NIXT]] and [[MSSTA]] sounding rockets in the 1990s, and it has been used to make telescopes for solar imaging. See also the [[Extreme Ultraviolet Explorer]] <!-- (EUVE) --> [[satellite]].{{cn|date=May 2024}}

Some sources use the distinction of "hard UV" and "soft UV". For instance, in the case of [[astrophysics]], the boundary may be at the [[Lyman limit]] (wavelength 91.2&nbsp;nm, the energy needed to ionise a hydrogen atom from its ground state), with "hard UV" being more energetic;<ref>
{{cite book
 |first1=John |last1=Bally
 |first2=Bo |last2=Reipurth
 |year=2006
 |title=The Birth of Stars and Planets
 |page=177
 |publisher=Cambridge University Press
}}
</ref> the same terms may also be used in other fields, such as [[cosmetology]], [[optoelectronic]], etc. The numerical values of the boundary between hard/soft, even within similar scientific fields, do not necessarily coincide; for example, one applied-physics publication used a boundary of 190&nbsp;nm between hard and soft UV regions.<ref>
{{cite journal
 |last1=Bark     |first1=Yu B.    |last2=Barkhudarov   |first2=E.M.
 |last3=Kozlov   |first3=Yu N.    |last4=Kossyi        |first4=I.A.
 |last5=Silakov  |first5=V.P.     |last6=Taktakishvili |first6=M.I.
 |last7=Temchin  |first7=S.M.
 |year=2000
 |title=Slipping surface discharge as a source of hard UV radiation
 |journal=Journal of Physics D: Applied Physics
 |volume=33  |number=7  |pages=859–863
 |bibcode=2000JPhD...33..859B  |doi=10.1088/0022-3727/33/7/317
|s2cid=250819933 }}
</ref>