Editing Lise Meitner (section)

==Beta radiation==
In 1921, Meitner accepted an invitation from [[Manne Siegbahn]] to come to Sweden and give a series of lectures on radioactivity as a visiting professor at [[Lund University]]. She found that very little research had been done on radioactivity in Sweden, but she was eager to learn about [[X-ray spectroscopy]], which was Siegbahn's specialty. At his laboratory, she met a Dutch doctoral candidate, [[Dirk Coster]], who was studying X-ray spectroscopy, and his wife Miep, who was working on her doctorate in Indonesian language and culture. Armed with her newly acquired knowledge of X-ray spectroscopy, Meitner took a fresh look at the beta-ray spectra when she returned to Berlin.{{sfn|Sime|1996|pp=653–657}} It was known that some beta emission was primary, with electrons being ejected directly from the nucleus, and some was secondary, in which alpha particles from the nucleus knocked electrons out of orbit. Meitner was sceptical of Chadwick's claim that the [[spectral line]]s were entirely due to secondary electrons, while the primary ones formed a continuous spectrum.{{sfn|Watkins|1983|pp=552–553}} Using techniques developed by [[Jean Danysz]], she examined the spectra of lead-210, [[radium-226]] and [[thorium-238]].{{sfn|Sime|1996|p=86}} Meitner discovered the cause of the emission of electrons from surfaces of atoms with "signature" energies, now known as the [[Auger-Meitner effect]], in 1922.{{sfn|Sime|1996|p=90}}<ref>{{Cite journal |last1 =Meitner |first1=L. |doi=10.1007/BF01326962 |title=Über die Entstehung der β-Strahl-Spektren radioaktiver Substanzen |language=de |trans-title=On the origin of the β-ray spectra of radioactive substances |journal=Zeitschrift für Physik |issn=0044-3328 |volume=9 |issue=1 |pages=131–144 |year=1922 |bibcode=1922ZPhy....9..131M |s2cid=121637546 }}</ref> The effect is co-named after [[Pierre Victor Auger]], who independently discovered it in 1923.<ref>{{cite journal |first=P. |last=Auger |author-link=Pierre Victor Auger |url=http://gallica.bnf.fr/ark:/12148/bpt6k3130n.image.f187.langFR |title=Sur les rayons β secondaires produits dans un gaz par des rayons X |language=fr |trans-title=On the secondary β-rays produced in a gas by X-rays |journal=Comptes rendus hebdomadaires des séances de l'Académie des sciences |volume=177 |date=1923 |pages=169–171 |access-date=30 May 2011 |archive-date=15 October 2017 |archive-url=https://web.archive.org/web/20171015233109/http://gallica.bnf.fr/ark:/12148/bpt6k3130n.image.f187.langFR |url-status=live }}</ref><ref>Meitner published before Auger, but the effect does not bear her name. The issue of whether Meitner's name should have been included is examined in: {{cite journal |title=Pierre Auger – Lise Meitner: Comparative contributions to the Auger effect |first=Olivier Hardouin |last=Duparc |journal=International Journal of Materials Research |issn=1862-5282 |volume=100 |issue=9 |date=2009 |pages=1162–1166 |doi=10.3139/146.110163 |bibcode=2009IJMR..100.1162H |s2cid=229164774 }}, {{cite journal |title=A Renaming Proposal: "The Auger–Meitner effect" |first1=Demetrios |last1=Matsakis |first2=Anthea |last2=Coster |first3=Brenda |last3=Laster |first4=Ruth |last4=Sime |author-link4=Ruth Lewin Sime |journal=Physics Today |issn=0031-9228 |volume=72 |issue=9 |pages=10–11 |date=September 2019 |doi=10.1063/PT.3.4281|bibcode=2019PhT....72i..10M }} and {{cite journal |first=Richard |last=Sietmann |year=1988 |journal=Physics Bulletin |title=False Attribution: a Female Physicist's Fate |issn=0031-9112 |volume=39 |issue=8 |pages=316–317 |doi=10.1088/0031-9112/39/8/017 }}</ref>

[[File:Bohr Heisenberg Pauli Meitner u.a. 1937 (cropped).jpg|thumb|right|upright=1.3|At a conference in 1937, Meitner shares the front row with (left to right) [[Niels Bohr]], [[Werner Heisenberg]], [[Wolfgang Pauli]], [[Otto Stern]], [[Rudolf Ladenburg]] and [[Jacob Christian Georg Jacobsen]]; [[Hilde Levi]] (at the very back) is the only other woman in the room.]]

Women were granted the right of habilitation in Prussia in 1920, and in 1922 Meitner was granted her habilitation and became a {{lang|de|[[Privatdozentin]]}}. She was the first woman to receive her habilitation in physics in Prussia, and only the second in Germany after [[Hedwig Kohn]]. Since Meitner had already published over 40 papers, she was not required to submit a thesis, but [[Max von&nbsp;Laue]] recommended that the requirement for an inaugural lecture not be waived, since he was interested in what she had to say. She therefore gave an inaugural lecture on "Problems of Cosmic Physics".{{sfn|Sime|1996|pp=109–110, 421}} From 1923 to 1933, she taught a [[seminar|colloquium]] or [[tutorial]] at Friedrich Wilhelm University each semester, and supervised doctoral students at the KWI for Chemistry.{{sfn|Sime|1996|pp=109–110, 421}} In 1926, she became an {{lang|de|[[außerordentlicher Professor]]}} ({{gloss|extraordinary professor}}), the first woman university physics professor in Germany. Her physics section became larger, and she acquired a permanent assistant. Scientists from Germany and around the world came to the KWI for Chemistry to conduct research under her supervision.{{sfn|Sime|1996|pp=109–110, 421}} In 1930, Meitner taught a seminar on "Questions of Atomic Physics and Atomic Chemistry" with [[Leó Szilárd]].{{sfn|Lanouette|Silard|1992|pp=100–101}}

[[File:Auger Process.svg|thumb|left|Two views of the [[Auger−Meitner effect]]. An incident electron or photon creates a core hole in the 1s level. An electron from the 2s level fills in the 1s hole and the transition energy is imparted to a 2p electron which is emitted. The final atomic state thus has two holes.]]

Meitner had a [[Wilson cloud chamber]] constructed at the KWI for Chemistry, the first one in Berlin, and with her student Kurt Freitag studied the tracks of alpha particles that did not collide with a nucleus.{{sfn|Sime|1996|p=113}} With her assistant Kurt Philipp she later used it to take the first images of [[positron]] traces from gamma radiation. She proved Chadwick's assertion that the discrete spectral lines were entirely the result of secondary electrons, and the continuous spectra were therefore indeed entirely caused by the primary ones. In 1927, [[Charles Drummond Ellis]] and William Alfred Wooster measured the energy of the continuous spectrum produced by the beta decay of [[bismuth-210]] at 0.34&nbsp;[[MeV]] where the energy of each disintegration was 0.35&nbsp;MeV. Thus, the spectrum accounted for nearly, but not all, of the energy. Meitner found this result so troubling that she repeated the experiment with [[Wilhelm Orthmann]] using an improved method, and verified Ellis and Wooster's results.{{sfn|Watkins|1983|pp=552–553}}<ref>{{cite journal |doi=10.1038/119563c0 |title=The Continuous Spectrum of β-Rays |journal=Nature |issn=0028-0836 |volume=119 |issue=2998 |pages=563–564 |year=1927 |last1=Ellis |first1=C. D. |author-link=Charles Drummond Ellis |last2=Wooster|first2=W. A. |s2cid=4097830 |bibcode=1927Natur.119..563E}}</ref><ref>{{cite journal |first1=L. |last1=Meitner |first2=Wilhelm |last2=Orthmann |author-link2=Wilhelm Orthmann |title=Über eine absolute Bestimmung der Energie der primären ß-Strahlen von Radium E |trans-title=On an Absolute Determination of the Energy of the Primary ß-Rays of Radium E |language=de |journal=Zeitschrift für Physik |issn=0044-3328 |volume=60 |issue=3–4 |pages=143–155 |date=March 1930 |doi=10.1007/BF01339819|s2cid=121406618 }}</ref>

It appeared that the [[law of conservation of energy]] did not hold for beta decay, something Meitner regarded as unacceptable. In 1930, [[Wolfgang Pauli]] wrote an open letter to Meitner and [[Hans Geiger]] in which he proposed that the continuous spectrum was caused by the emission of a second particle during beta decay, one that had no electric charge and little or no [[rest mass]]. The idea was taken up by [[Enrico Fermi]] in his 1934 [[Fermi's interaction|theory of beta decay]], and he gave the name "[[neutrino]]" to the hypothetical neutral particle. At the time there was scant hope of detecting neutrinos, but in 1956 [[Clyde Cowan]] and [[Frederick Reines]] did just that.{{sfn|Watkins|1983|pp=552–553}}