Starting from Rainwater's concept of an irregular-shapedliquid drop model of the nucleus, Bohr and Mottelson developed a detailed theory that was in close agreement with experiments.
Since his father, Niels Bohr, had won the prize in 1922, he and his father are one of the several pairs of fathers and sons who have both won the Nobel Prize.[2][3]
Bohr was born inCopenhagen on 19 June 1922, the fourth of six sons of the physicistNiels Bohr and his wifeMargrethe Bohr (née Nørlund).[4] His oldest brother, Christian, died in a boating accident in 1934,[5] and his youngest, Harald, was severely disabled and placed away from the home in Copenhagen at the age of four.[6] He would later die from childhood meningitis.[7] Of the others, Hans became a physician; Erik, a chemical engineer; andErnest, a lawyer and Olympic athlete who playedfield hockey for Denmark at the1948 Summer Olympics in London.[8][9] The family lived at the Institute of Theoretical Physics at theUniversity of Copenhagen, now known as theNiels Bohr Institute, where he grew up surrounded by physicists who were working with his father, such asHans Kramers,Oskar Klein,Yoshio Nishina,Wolfgang Pauli andWerner Heisenberg.[4] In 1932, the family moved to the Carlsberg Æresbolig, a mansion donated byCarl Jacobsen, the heir toCarlsberg breweries, to be used as an honorary residence by the Dane who had made the most prominent contribution to science, literature, or the arts.[10]
Bohr went to high school at Sortedam Gymnasium in Copenhagen. In 1940, shortly after theGerman occupation of Denmark in April, he entered the University of Copenhagen, where he studied physics. He assisted his father, helping draft correspondence and articles related toepistemology and physics.[4] In September 1943, word reached his family that the Nazis considered them to be Jewish, because Bohr's grandmother, Ellen Adler Bohr, had been Jewish, and that they therefore were in danger of being arrested. TheDanish resistance helped the familyescape by sea to Sweden.[11] Bohr arrived there in October 1943, and then flew to Britain on ade Havilland Mosquito operated byBritish Overseas Airways Corporation. The Mosquitoes were unarmed high-speed bomber aircraft that had been converted to carry small, valuable cargoes or important passengers. By flying at high speed and high altitude, they could crossGerman-occupied Norway, and yet avoid German fighters. Bohr, equipped with a parachute, flying suit, and oxygen mask, spent the three-hour flight lying on a mattress in the aircraft'sbomb bay.[12]
On arrival in London, Bohr rejoined his father, who had flown to Britain the week before.[12] He officially became a junior researcher at theDepartment of Scientific and Industrial Research, but actually served as personal assistant and secretary to his father. The two worked onTube Alloys, the Britishatomic bomb project. On 30 December 1943, they made the first of a number of visits to the United States, where his father was a consultant to theManhattan Project.[13] Due to his father's fame, they were given false names; Bohr became James Baker, and his father, Nicholas Baker.[14] In 1945, the director of theLos Alamos Laboratory,J. Robert Oppenheimer, asked them to review the design of themodulated neutron initiator. They reported that it would work. That they had reached this conclusion putEnrico Fermi's concerns about the viability of the design to rest.[14] The initiators performed flawlessly in the bombs used in theatomic bombings of Hiroshima and Nagasaki in August 1945.[15]
In August 1945, with the war ended, Bohr returned to Denmark, where he resumed his university education, graduating with a master's degree in 1946, with a thesis concerned with some aspects ofatomic stopping power problems.[4] In early 1948, Bohr became a member of theInstitute for Advanced Study inPrinceton, New Jersey.[16] While paying a visit toColumbia University, he metIsidor Isaac Rabi, who sparked in him an interest in recent discoveries related to thehyperfine structure ofdeuterium. This led to Bohr becoming a visiting fellow at Columbia from January 1949 to August 1950.[4][17] While in the United States, Bohr married Marietta Soffer on 11 March 1950. They had three children: Vilhelm, Tomas and Margrethe.[17]
By the late 1940s it was known that the properties ofatomic nuclei could not be explained by then-current models such as theliquid drop model developed by Niels Bohr amongst others. Theshell model, developed in 1949 byMaria Goeppert Mayer and others, allowed some additional features to be explained, in particular the so-calledmagic numbers. However, there were also properties that could not be explained, including the non-spherical distribution of charge in certain nuclei.[18] In a 1950 paper,James Rainwater of Columbia University suggested a variant of the drop model of the nucleus that could explain a non-spherical charge distribution.[19] Rainwater's model postulated a nucleus like a balloon with balls inside that distort the surface as they move about. He discussed the idea with Bohr, who was visiting Columbia at the time, and had independently conceived the same idea, and had, about a month after Rainwater's submission, submitted for publication a paper that discussed the same problem, but along more general lines. Bohr imagined a rotating, irregular-shaped nucleus with a form of surface tension.[20] Bohr developed the idea further, in 1951 publishing a paper that comprehensively treated the relationship between oscillations of the surface of the nucleus and the movement of the individualnucleons.[21]
Upon his return to Copenhagen in 1950, Bohr began working withBen Roy Mottelson to compare the theoretical work with experimental data. In three papers, that were published in 1952 and 1953, Bohr and Mottelson demonstrated close agreement between theory and experiment; for example, showing that the energy levels of certain nuclei could be described by a rotation spectrum.[22][23][24] They were thereby able to reconcile the shell model with Rainwater's concept.[20] This work stimulated many new theoretical and experimental studies.[18] Bohr, Mottelson and Rainwater were jointly awarded the 1975Nobel Prize in Physics "for the discovery of the connection between collective motion and particle motion in atomic nuclei and the development of the theory of the structure of the atomic nucleus based on this connection".[1] Because his father had been awarded the prize in 1922, Bohr became one of only four pairs of fathers and sons to win the Nobel Prize in Physics.[25]
Only after doing his Nobel Prize-winning research did Bohr receive his doctorate from the University of Copenhagen, in 1954, writing his thesis on "Rotational States of Atomic Nuclei".[26] Bohr became a professor at the University of Copenhagen in 1956, and, following his father's death in 1962, succeeded him as director of the Niels Bohr Institute, a position he held until 1970. He remained active there until he retired in 1992.[27] He was also a member of the board of theNordic Institute for Theoretical Physics from its inception in 1957, and was its director from 1975 to 1981.[28] In addition to the Nobel Prize, he won theDannie Heineman Prize for Mathematical Physics in 1960, theAtoms for Peace Award in 1969,H. C. Ørsted Medal in 1970,Rutherford Medal and Prize in 1972,John Price Wetherill Medal in 1974, and the Ole Rømer medal in 1976.[16][29][30] Bohr and Mottelson continued to work together, publishing a two-volumemonograph,Nuclear Structure. The first volume,Single-Particle Motion, appeared in 1969; the second,Nuclear Deformations, in 1975.[4]
Bohr's wife Marietta died in 1978. In 1981, he married Bente Scharff Meyer.[37] His son, Tomas Bohr, is a professor of physics at theTechnical University of Denmark, working in the area offluid dynamics.[38] Aage Bohr died in Copenhagen on 9 September 2009.[27] He was survived by his second wife and children.[37]
Bohr'sNobel Prize medal was sold at auction in November 2011. It was subsequently sold at auction in April 2019 for $90,000.[39]
^abLewin, Roger; Sherwood, Martin; Walgate, Robert (23 October 1975). "Nobel Prizes 1975: Medicine, Chemistry and Physics … and fifty years ago".New Scientist.68 (972).ISSN0262-4079.
