Editing Laser cooling (section)

=== Radiation pressure ===
[[Radiation pressure]] is the force that electromagnetic radiation exerts on matter.  In 1873 Maxwell published his treatise on [[electromagnetism]] in which he predicted radiation pressure.<ref name="Maxwell1873">
{{cite book| title=A Treatise on Electricity and Magnetism, II|edition= 1st| author-link=James Clerk Maxwell| first=J.C.| last=Maxwell| year=1873| location=Oxford| page=391}}
</ref> The force was experimentally demonstrated for the first time by [[Pyotr Lebedev|Lebedev]] and reported at a conference in Paris in 1900,<ref name="Lebedev1900">
{{cite conference| url=https://www.europhysicsnews.org/articles/epn/pdf/2019/04/epn2019504p15.pdf| title=Les forces de Maxwell-Bartoli dues à la pression de la lumière| first=Pyotr| last=Lebedew| year=1900| conference=Rapports présentés au Congrès International de Physique | volume=2| location=Paris| page=133 |language=fr|author-link= Pyotr Lebedev}}
</ref> and later published in more detail in 1901.<ref name="Lebedew1901">
{{cite journal
 |last=Lebedew |first=P. |author-link= Pyotr Lebedev
 |year=1901
 |title=Untersuchungen über die Druckkräfte des Lichtes
 |journal=[[Annalen der Physik]]
 |language=de
 |volume=311 |issue=11 |pages=433–458
 |bibcode=1901AnP...311..433L
 |doi=10.1002/andp.19013111102
 |url=https://zenodo.org/record/1424005
}}</ref> Following Lebedev's measurements [[Ernest Fox Nichols|Nichols]] and [[Gordon Ferrie Hull|Hull]] also demonstrated the force of radiation pressure in 1901,<ref name="Nichols1901">
{{cite journal|last1=Nichols |first1=E.F. |last2=Hull |first2=G.F. |author1-link=Ernest Fox Nichols |author2-link=Gordon Ferrie Hull|title=A Preliminary Communication on the Pressure of Heat and Light Radiation|url=https://link.aps.org/doi/10.1103/PhysRevSeriesI.13.307|journal=Physical Review |series=Series I |doi=10.1103/PhysRevSeriesI.13.307 |year=1901|volume=13 |issue=5 |pages=307–320 |bibcode=1901PhRvI..13..307N }}
</ref> with a refined measurement reported in 1903.<ref name="Nichols1">
{{cite journal|last1=Nichols |first1=E.F. |last2=Hull |first2=G.F. |author1-link=Ernest Fox Nichols |author2-link=Gordon Ferrie Hull|title=The Pressure Due To Radiation . (Second Paper.) <!--DUPLICATE|url=http://massey.dur.ac.uk/articles/newoptics.pdf--> | year=1903 | pages=26–50| volume=17 | url=https://journals.aps.org/pri/abstract/10.1103/PhysRevSeriesI.17.26| journal=Physical Review|issue=1 |doi=10.1103/PhysRevSeriesI.17.26 |bibcode=1903PhRvI..17...26N }}
</ref><ref name="Nichols2">
{{cite journal|last1=Nichols |first1=E.F. |last2=Hull |first2=G.F. |author1-link=Ernest Fox Nichols |author2-link=Gordon Ferrie Hull|title=The Pressure Due To Radiation. (Second Paper.) <!--DUPLICATE|url=http://massey.dur.ac.uk/articles/newoptics.pdf--> | year=1903 | pages=91–104| volume=17 | url=https://journals.aps.org/pri/abstract/10.1103/PhysRevSeriesI.17.91| journal=Physical Review|issue=2 |doi=10.1103/PhysRevSeriesI.17.91 |bibcode=1903PhRvI..17...91N }}
</ref> 

Atoms and molecules have bound states and transitions can occur between these states in the presence of light that is near the transition frequency.  Sodium is historically notable because it has a strong transition at 589 nm, a wavelength which is close to the peak sensitivity of the human eye.  This made it relatively easy to see the interaction of light with sodium atoms.  In 1933, [[Otto Frisch]] deflected an atomic beam of sodium atoms with light.<ref name="Frisch">
{{cite journal|last=Frisch|first=R. |title= Experimenteller Nachweis des Einsteinschen Strahlungsrückstoßes |url=https://link.springer.com/article/10.1007/BF01340182| year=1933 | pages=42–48| volume=86 | language=de|journal=Zeitschrift für Physik|issue=1–2 |doi=10.1007/BF01340182 |bibcode=1933ZPhy...86...42F |s2cid=123038196 }}
</ref> 
This was the first realization of radiation pressure acting on an atom or molecule.