Editing Laser cooling (section)

==== Exotic Atoms ====
Most laser cooling experiments bring the atoms close to at rest in the laboratory frame, but cooling of relativistic atoms has also been achieved, where the effect of cooling manifests as a narrowing of the velocity distribution. In 1990, a group at [[Johannes Gutenberg-Universität Mainz|JGU]] successfully laser-cooled a beam of <sup>7</sup>Li<sup>+</sup> at {{val|13.3|u=MeV}} in a storage ring <ref>{{cite journal |last1=Schröder |first1=S. |last2=Klein |first2=R. |last3=Boos |first3=N. |last4=Gerhard |first4=M. |last5=Grieser |first5=R. |last6=Huber |first6=G. |last7=Karafillidis |first7=A. |last8=Krieg |first8=M. |last9=Schmidt |first9=N. |last10=Kühl |first10=T. |last11=Neumann |first11=R. |last12=Balykin |first12=V. |last13=Grieser |first13=M. |last14=Habs |first14=D. |last15=Jaeschke |first15=E. |last16=Krämer |first16=D. |last17=Kristensen |first17=M. |last18=Music |first18=M. |last19=Petrich |first19=W. |last20=Schwalm |first20=D. |last21=Sigray |first21=P. |last22=Steck |first22=M. |last23=Wanner |first23=B. |last24=Wolf |first24=A. |title=First laser cooling of relativistic ions in a storage ring |journal=Physical Review Letters |date=11 June 1990 |volume=64 |issue=24 |pages=2901–2904 |doi=10.1103/PhysRevLett.64.2901|pmid=10041842 |bibcode=1990PhRvL..64.2901S }}</ref> from {{val|260|u=K}} to lower than {{val|2.9|u=K}}, using two counter-propagating lasers addressing the same transition, but at {{val|514.5|u=nm}} and {{val|584.8|u=nm}}, respectively, to compensate for the large [[Doppler effect|Doppler shift]]. 

Laser cooling of antimatter has also been demonstrated, first in 2021 by the [[ALPHA experiment|ALPHA]] collaboration on antihydrogen atoms.<ref>{{cite journal |last1=Baker |first1=C. J. |last2=Bertsche |first2=W. |last3=Capra |first3=A. |last4=Carruth |first4=C. |last5=Cesar |first5=C. L. |last6=Charlton |first6=M. |last7=Christensen |first7=A. |last8=Collister |first8=R. |last9=Mathad |first9=A. Cridland |last10=Eriksson |first10=S. |last11=Evans |first11=A. |last12=Evetts |first12=N. |last13=Fajans |first13=J. |last14=Friesen |first14=T. |last15=Fujiwara |first15=M. C. |last16=Gill |first16=D. R. |last17=Grandemange |first17=P. |last18=Granum |first18=P. |last19=Hangst |first19=J. S. |last20=Hardy |first20=W. N. |last21=Hayden |first21=M. E. |last22=Hodgkinson |first22=D. |last23=Hunter |first23=E. |last24=Isaac |first24=C. A. |last25=Johnson |first25=M. A. |last26=Jones |first26=J. M. |last27=Jones |first27=S. A. |last28=Jonsell |first28=S. |last29=Khramov |first29=A. |last30=Knapp |first30=P. |last31=Kurchaninov |first31=L. |last32=Madsen |first32=N. |last33=Maxwell |first33=D. |last34=McKenna |first34=J. T. K. |last35=Menary |first35=S. |last36=Michan |first36=J. M. |last37=Momose |first37=T. |last38=Mullan |first38=P. S. |last39=Munich |first39=J. J. |last40=Olchanski |first40=K. |last41=Olin |first41=A. |last42=Peszka |first42=J. |last43=Powell |first43=A. |last44=Pusa |first44=P. |last45=Rasmussen |first45=C. Ø |last46=Robicheaux |first46=F. |last47=Sacramento |first47=R. L. |last48=Sameed |first48=M. |last49=Sarid |first49=E. |last50=Silveira |first50=D. M. |last51=Starko |first51=D. M. |last52=So |first52=C. |last53=Stutter |first53=G. |last54=Tharp |first54=T. D. |last55=Thibeault |first55=A. |last56=Thompson |first56=R. I. |last57=van der Werf |first57=D. P. |last58=Wurtele |first58=J. S. |title=Laser cooling of antihydrogen atoms |journal=Nature |date=April 2021 |volume=592 |issue=7852 |pages=35–42 |doi=10.1038/s41586-021-03289-6|pmid=33790445 |pmc=8012212 |bibcode=2021Natur.592...35B }}</ref> In 2024, [[Positronium|positronium]], made up of an electron and a positron, was laser cooled to about 1K.<ref>{{cite journal |last1=Shu |first1=K. |last2=Tajima |first2=Y. |last3=Uozumi |first3=R. |last4=Miyamoto |first4=N. |last5=Shiraishi |first5=S. |last6=Kobayashi |first6=T. |last7=Ishida |first7=A. |last8=Yamada |first8=K. |last9=Gladen |first9=R. W. |last10=Namba |first10=T. |last11=Asai |first11=S. |last12=Wada |first12=K. |last13=Mochizuki |first13=I. |last14=Hyodo |first14=T. |last15=Ito |first15=K. |last16=Michishio |first16=K. |last17=O’Rourke |first17=B. E. |last18=Oshima |first18=N. |last19=Yoshioka |first19=K. |title=Cooling positronium to ultralow velocities with a chirped laser pulse train |journal=Nature |date=September 2024 |volume=633 |issue=8031 |pages=793–797 |doi=10.1038/s41586-024-07912-0|pmid=39261730 |arxiv=2310.08761 |bibcode=2024Natur.633..793S }}</ref>