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JERROLD R. ZACHARIAS January 23, 1 905-July 1 6' 1 986 BY N O RMAN F . RAMSEY JERROLD ZACHARIAS MADE important, creative, and lasting con- tributions to physics, national defense, and education. He participated in the first molecular beam magnetic reso- nance experiments; he measured nuclear magnetic moments and electric quadrupole moments of various nuclei, includ- ing the proton and cleuteron; he confirmed the anomalous hyperf~ne separation in atomic hydrogen; and he clevelope the first commercial atomic clocks. During World War II, he clevelope(1 radar systems at MIT and nuclear weapons at Los Alamos. In the years following the war he initiated and led important national defense studies. As a result of his creep concerns about science education in the United States, he initiated numerous fruitful studies to improve it. He established the Physical Sciences Stucly Committee (PSSC), which not only made successful recommendations but also stimulated the production of movies and textbooks. The PSSC became a model for similar educational reforms in mathematics ant! most other sciences. EARLY YEARS JerroIcl Zacharias was born on January 23, 1905, in Jack- sonville, Florida. His father, Isaclore, was a lawyer with in- terests in real estate, and his mother was a taTentecl violin- 435

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436 BIOGRAPHICAL MEMOIRS ist. His childhoocI and education are well describer! in an excellent biography by Jack S. Goicistein.~ {erroIcI had little interest in music, while his sister, Dorothea, anct his adopted brother, Beryl Rubenstein, were talentecl musicians. Their musical mother was consequently less interested in Errol, who found real companionship in his nurse, Anna Liza Johnson, who later carecl for Jerroicl's children in New York City. JerroIcl's interest in physics began at age four with a fasci- nation with his grancifather's automobile and continued into his teens with interests in photography, crystal set raclio, and the Tom Swift books. Although he received excellent gracles in high school, including his first physics course, JerroIcI later complained that he clict not learn much. Soon after graduation from high school, his family moved to Riverside Drive in New York City, where JerroIc3 enterer! Columbia as an engineering student. By his sophomore year, he fount! physics challenged him more than engineering, so he changed to a major in mathematics with a minor in physics. ierrold clic! well as an unclergracluate but later cle- scribed himself as having been a fraternity playboy with a generous allowance, a raccoon coat, en cl a Packarc! touring car. In 1925 as a Columbia undergracluate, ierroIcI, on a blind (late, met Leona Hurwitz, a delightful, serious biol- ogy major at Barnard. They married two years later. Leona remained his lifelong companion and became the mother of Susan en c] Johanna. After graduating, Errol enterer! Columbia graduate school en cl began research with Shirley Quimby in solid state phys- ics, a barely recognized research f~elcl at that time. Qulmby suggested the problem of measuring the stress-strain rela- tionship (Young's mocluTus) and internal friction in crystals of nickel by studying their vibrations. Zacharias discovered an unexpected diminution of internal friction of the crys-

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JERROLD R. ZACHARIAS 437 tats at the Curie temperature, where their magnetic proper- ties also change dramatically. RESEARCH AT COLUMBIA JerroIcl Zacharias completed his thesis research in 1931- the middle of the great depression, when few jobs were available. He succeecled in obtaining an appointment as a tutor at Hunter College at a salary of $2,000 per year and with a heavy teaching schedule. Zacharias was an excellent teacher but was eager to re- turn to experimental research as well, so, in adclition to his Hunter teaching duties, he soon arranger! to work with I. T. Rabi of Columbia University. He spent his free evenings ant! weekends in Rabi's atomic beam laboratory as an un- paicl research associate. Rabi had invented an atomic beam methoc! for measuring the magnetic moments of nuclei by their interaction with the magnetic moment of the elec- tron, which affecter! how the atom would be (leflectec! by an inhomogeneous magnetic fielcI. With his first graduate student, Victor Cohen, Rabi was applying this method to the measurement of the nuclear magnetic moments of so- clium and cesium. Zacharias was especially interested in sim- pler fundamental atoms, so he joined with Rabi and Jerome M. B. Kellogg, a young Columbia instructor newly arrived from Towa, on the more difficult task of measuring the nuclear magnetic moments of hydrogen and deuterium. They con- firmect Otto Stern's earlier observation that the magnetic moment of the proton was much larger than the theoreti- cally expected value of one nuclear magneton. These ob- servations provident the first indications that the proton hacI a complex internal structure. Later Zacharias and his asso- ciates improved their results by using the new zero moment method and then further mortifies! their apparatus to mea-

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438 BIOGRAPHICAL MEMOIRS sure the signs of the proton and deuteron magnetic mo- ments. In the summer of 1937, Zacharias, S. MilIman, P. Kusch, and Rabi measured the magnetic moments of inclium and gallium anc! found a small contribution to the deflection patterns from the thermally excited higher energy states. By studying these contributions they couict also measure the nuclear quacirupole moments of these nuclei. With char- acteristic humor, ~erroIcl clescribed this period! of research as indium summer. T had the good fortune to join the Co- lumbia atomic beam laboratory at this time and to work on this experiment as an apprentice. It was a great experience and T Earned much, ranging from apparatus design and vacuum techniques to ciata analysis and theoretical prin- ciples. Although Jerrold had not yet acquired his fame in science education, he was a talentecl teacher. He taught me one particularly memorable lesson. T hacl just given what seemed to be a highly successful colloquium and ferrous asked me to hanc! him my third slide. Instead of the ex- pected question about its contents, he dramatically broke the sTicle over the edge of the lecture table en c! said, "Don't ever again show a slicle that cannot be react from the back of the room" a painful lesson ~ have never forgotten. In 1937 {erroIcI was appointee! assistant professor at Hunter College and Leona obtainer! her Ph.D. and an appoint- ment as instructor at the Columbia College of Physicians en c! Surgeons. Also in 1937 the research at Columbia was revolutionized by Rabi's invention of the magnetic resonance method. The first successful experiment with this methoc! was by Rabi, Miliman, Kusch, en cl Zacharias. This experiment was the forerunner of many different kinds of resonance experi- ments, including nuclear magnetic resonance and paramag- netic resonance. The first resonance experiment was soon

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JERROLD R. ZACHARIAS 439 followed by the experiments of Kellogg, Rabi, Ramsey, and Zacharias, which not only obtained accurate values for the proton and deuteron magnetic moments but also discov- ered the electric quadrupole moment of the deuteron, which in turn showed the existence of a new kind of force a tensor forcebetween the proton and neutron. Zacharias then turned his attention to measuring the magnetic moment of 40K, since some theorists had predicted that its unusually long lifetime might be associated with a large nuclear magnetic moment. The measurement was suc- cessful though difficult because only one atom in 10,000 of natural potassium is 40K. In 1940 ~errold and T were invited to give talks on our magnetic and electric dipole moment measurements at a meeting of the American Physical Soci- ety in Seattle, Washington, so Jerrold drove my new wife and me cross country to Seattle and then back to Glacier Park where we were joined by l~eona. The trip was scientifi- cally and scenically exciting but politically distressing since the Nazis were moving through France almost as rapidly as we moved across the United States. It appeared that the war would soon be upon us. THE WAR YEARS Our fears soon proved to be valid; within the next four months Zacharias, Rabi, and T had moved to the MIT Ra- diation Laboratory, where we worked on microwave radar. Zacharias's first task at MTT was to establish a lab on the MIT roof and build a radar system there capable of detect- ing distant objects. His success led to his being asked by the Navy to install a radar set on a destroyer. When this was successfully completed, Zacharias became the Radiation Laboratory representative at the Bell Telephone Laborato- ries in Whippany, New Jersey, during the development of a production model for the MIT 10-cm night fighter radar.

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440 BIOGRAPHICAL MEMOIRS He then went to England to adapt the Oboe blind bombing system from long wavelengths to microwaves. He returned to the Racliation Laboratory to head the Transmitter Com- ponents Division, and in the spring of 1945 he accepted the offer of a full professorship at MTT while remaining on leave to continue his racier research. Zacharias left MIT to go to Los Alamos a few months before the end of the war to head the Orcinance Engineer- ing Division, a position vacated by Captain (later Aclmiral) W. S. Parsons, who hac! left for the Pacific isTanct of Tinian. That division later became the Z division, which evolved into the Sanclia National Laboratories. NUCLEAR SCIENCE, ATOMIC BEAMS, AND ATOMIC CLOCKS At the war's end Jerrold Zacharias returned to MTT as professor of Physics en c] director of the newly established Laboratory for Nuclear Science en cl Engineering. He quickly arranged for financial support from the newly established Office of Naval Research en c! organized a strong research staff, inclucling B. Rossi, I. G. Trump, M. Deutsch, R. I. Van c3 eGraff, R. D. Evans, I. A. Getting, V. F. Weisskopf, M. Benedict, and C. D. Coryell. Zacharias was also an MIT representative on the Initiatory University Group en cl later the Associates! Universities, Inc. (AUl), which establishecI Brookhaven National Laboratory. Zacharias and his associates establisher! a vigorous and effective atomic beam research laboratory. They indepen- dently confirmed! that the experimental value of the atomic hydrogen hyperfine structure disagreed with the theoreti- cal value, a disagreement that stimulated the clevelopment of relativistic quantum electroclynamics. They measurer] a number of nuclear spins ant! magnetic moments and for the first time detectecl a nuclear magnetic octupole mo- ment.

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JERROLD R. ZACHARIAS 441 Zacharias at this time became interested in developing atomic clocks en c! pursued two versions concurrently. One was a cesium atomic beam clock using my separates! oscilIa- tory fierce methoct,2 well engineered for reliability ant] com- mercial applications, including a source and vacuum sys- tem that could be operated for years rather than hours. He cooperated with the National Company in developing a com- mercial clock known as the Atomichron. The availability of this highly successful cesium atomic beam clock contrib- utec3 greatly to the adoption of atomic time and to the international definition of the second! as 9,192,631,770 os- cilIations of the cesium atom. His other version had the potential for much greater ac- curacy but the risk of total failure. A very slow beam of atomic cesium was directecI upward and allowed to fall as a fountain, with separates! oscillatory field excitation on the way up and clown. The half second required for the roundtrip in the fountain was approximately fifty times greater than that for an atom to traverse the oscillatory field region of a conventional atomic beam apparatus, so the resonance wraith, by the Heisenberg uncertainty principle, would be fifty times narrower with corresponclingly increased clock accuracy. Despite valiant efforts by Zacharias ant! his associates, the fountain experiment failed because the numbers of ultra- sIow atoms in the beam were far below theoretical predic- tions, probably clue to scattering in the nonequilibrium re- gion between the slits. It is of interest to note that thirty years later, in 1989, Steven Chu3 succeeded in making an atomic fountain by using the new laser cooling techniques to produce ultra-sIow atoms. The atomic fountain with laser cooling is now one of the most promising prospects for increasing the accuracy of clocks and frequency stanciarcts.

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442 BIOGRAPHICAL MEMOIRS DEFENSE STUDIES As the CoIcl War intensified in the late 1940s, Zacharias became involved in defense studies. The first of these was Project Lexington, commissioned by the Atomic Energy Commission in 1948 to study the feasibility of nuclear-pow- erecI aircraft. Although deputy director of the study, Zacharias was frustrates! by its being limited to the narrow question of the feasibility of nuclear-powerecl aircraft to the exclu- sion of the broacler questions of their practicality ant! clesir- ability. He learner! from this experience that later studies that he organizer! or directed must have broadly clefined ~ missions. For the Navy he clirectect Project Hartwell, on the threat by Soviet submarines. At his insistence the mission was so broadly definecl that the title of the final report was A Re- port on the Security of Overseas Transport. The conclusions included recommendations for a new high-speec! merchant fleet and modernization of port ant! cargo facilities as well as recommendations for submarine detection. In it951 Zacharias served as associate director of Project Charles, which was established to make recommendations on the air defense of the North American continent. The project recommencled tests of an experimental system of radars coupled through high-speecI digital computers ant! the establishment of a new laboratory (Lincoln Laboratory) to continue research on this problem. Jerrold later directed a 1952 I~incoin Laboratory study of air (lefense that recom- menclect establishment of the DEW (distant early warning) line, a chain of huge radars stretched across the Arctic and coupled to high-speec! computers to detect approaching missiles. In 1955 Zacharias ctirectect Project Lamp Light to study fleet ant! air defense. Many years later, during the Vietnam War, Zacharias di-

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JERROLD R. ZACHARIAS 443 rected one more Department of Defense study, this time on means for preventing the infiltration of men and materials across the demilitarized zone between North and South Viet- nam. The study recommended an electronic barrier as an alternative to air bombardment. EDUCATION REFORM In 1955, at the age of fifty and after ten years of service, Zacharias retired as director of MIT's Laboratory for Nuclear Science, and a year later he terminated his atomic beam research to devote himself to his newest interesteduca- tion reform, especially in the sciences. He deeply believed that the United States would suffer in the future from the inadequacy of its science education and that "in order to save our democracy, we've got to It the neonle who r - -r vote." Although his initial plans emphasized the development of a series of educational physics films, he approached the problems of education in the same broad manner that had been so successful in his defense studies. With the support of the National Science Foundation, he assembled a bril- liant array of individuals, including research physicists, teach- ers, scholars, writers, and motion picture directors, to form the Physical Sciences Study Committee (PSSC). The com- mittee agreed that an entirely new approach to physics edu- cation was required, including new textbooks, laboratory kits to provide firsthand experience with simple apparatus, films, supplementary reading materials, and teacher train- ing. The U.S. public reaction to the spectacular success of the Russian Sputnik in 1957 added urgency to the PSSC project. Talented new recruits joined the PSSC, which sub- sequently was well supported by the NSF and private orga- nizations such as the Alfred P. Sloan Foundation. Nearly sixty films were eventually produced by the PSSC

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444 BIOGRAPHICAL MEMOIRS with scientists rather than actors en c! with emphasis on fun- damental principles en c! on hoIcling student interest. A text- book was written and widely a(loptecT, along with teaching aids and new laboratory materials, including simple but in- formative experiments for schools with low budgets. Since good teachers are essential to the success of such a pro- gram, special summer institutes for teacher training were established. The PSSC influence extencled far beyond the teaching of high school physics in the United States. In universities physics courses were improver! to meet the changed knowI- ecige and expectations of entering students with PSSC ex- perience. The PSSC also server! as a moclel for similar stucI- ies and curriculum changes in mathematics and other sciences. The PSSC was followed with great interest abroad, en c! its textbooks were translated into more than twelve languages. Zacharias also became interested! in elementary school science problems and establisher! Educational Services, Inc. (ESI), under which a study was initiated to develop a sci- ence program for elementary schools. Eventually, this hacI a large impact on American education. His meetings ant! discussions about the problems of science education in Af- rica lecl to the African nations cooperating to establish a Science Education Program for Africa (SEPA). Zacharias's eclucational interests were not limiter! to sci- ence. He also encourageec! EST to establish the influential Social Studies Curriculum Program and the Negro College Program. A triple bypass coronary operation in 1977 only siowecl Zacharias as he continued to push for education reform. At the same time, his deep concerns about the threat of nuclear war tell him to coauthor a thoughtful essay titled Common

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lERROLD R. ZACHARIAS 445 Sense and Nuclear Peace. He died from coronary artery dis- ease on July 16, 1986, at the age of eighty-one. HONORS AND AWARDS Jerrold Zacharias received many honors and awards, in- cluding election to the National Academy of Sciences in 1~957 and to the American Academy of Arts and Sciences. He was a fellow of the American Physical Society, American Association for the Advancement of Science, and the Insti- tute of Electrical and Electronic Engineers. He was an insti- tute professor at MIT and a member of the American Asso- ciation of Physics Teachers (AAPT) and the President's Science Advisory Committee. The U.S. government awarded him the President's Certificate of Merit and the Depart- ment of Defense Certificate of Appreciation, its highest ci- vilian honor. He received the AAPT's Oersted Medal for his contributions to teaching, the National Teachers Associa- tion Citation for Distinguished Service to Science Educa- tion, and the T. I. Rabi Award "for technical excellence and outstanding contributions in the fields relating to atomic and molecular frequency standards." Zacharias also received honorary degrees from Tufts University, Oklahoma City University, St. Lawrence University, Lincoln University, and Brandeis University. SCIENCE, DEFENSE, AND EDUCATION Science, national defense, and education were all greatly changed by ~errold Zacharias. His work on the first molecu- lar beam magnetic resonance experiments led the way for later magnetic resonance techniques, such as nuclear mag- netic resonance (NMR) and magnetic resonance imaging (MRI). He and his associates measured numerous nuclear spins and magnetic moments and discovered the quadru- pole moment of the deuteron, which implied the existence

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446 BIOGRAPHICAL MEMOIRS of a new kind of nuclear force. His clevelopment of the first commercial atomic cesium beam clock eventually lect to the international adoption of the atomic cesium oscillations as the definition of the second. Zacharias's wartime work on racier increased the reliabil- ity, versatility, and effectiveness of racier. The studies he initiated cluring the coict war contributed importantly to national defense. The teaching of physics in many elementary and seconcl- ary schools was greatly changed by studies, such as PSSC, initiated by Zacharias and by new movies, classroom materi- als, and teacher training programs. The success of these programs in turn stimulatecI similar education reforms in other sciences and in other countries. In his scientific research his development of atomic clocks, and his defense and eclucational projects, {erroIcI Zacharias was not cleterrecI by formiciable obstacles. He attacked for- midable problems with enthusiasm en c! determination. His positive anti constructive attitude is well characterized by the remark of I. I. Rabi: "Dr. Zacharias is a man who, if he were to discuss the weather, would finish not by just talking about it, but he would be cloing something about it." NOTES 1. J. S. Goldstein. A Different Sort of Time: The Life of Jerrold R. Zacharias Cambridge, Mass.: MIT Press, 1992. This excellent biog- raphy is the source of much of my information about Zacharias's full and varied life and provides a much fuller account than can be presented in a brief memoir. 2. N. F. Ramsey. Molecular beam resonance method with sepa- rated oscillatory fields. Phys. Rev. 78 ( 1950) :695. 3. M. Kasevich, E. Riis, S. Chu, and R. S. DeVoe. RF spectros- copy in an atomic fountain. Phys. Rev. Letters (1989~:612.

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JERROLD R. ZACHARIAS SELECTED BIBLIOGRAPHY 1933 447 The temperature of Young's modulus for nickel. Phys. Rev. 44:116- 12. With A. Dingwell and S. Siegel. The contamination of nickel crys- tals grown in a molybdenum resistance furnace. Trans. Am. Electrochem. Soc. 63:395-400. 1934 With I. I. Rabi and {. M. B. Kellogg. The magnetic moment of the proton. Phys. Rev. 46:157-63. With I. I. Rabi and J. M. B. Kellogg. The magnetic moment of the deuteron. Phys. Rev. 46:163. 1936 With I. I. Rabi and T. M. B. Kellogg. The sign of the magnetic moment of the proton. Nature 137:658. With J. M. B. Kellogg and I. I. Rabi. The gyromagnetic properties of the hydrogens. Phys. Rev. 50:472. 1937 With S. Millman. Signs of the nuclear magnetic moments of Li7, Rb85, and Cs~35. Phys. Rev. 51:1049. 1938 With I. I. Rabi, S. Millman, and P. Kusch. New method of measur- ing nuclear magnetic moment. Phys. Rev. 53:318. With S. Millman and I. I. Rabi. On the nuclear moments of indium. Phys. Rev. 53:384-91. With I. I. Rabi, S. Millman, and P. Kusch. Magnetic moments of 3Li6, 3Li7, and gFi9. Phys. Rev. 53:495. 1939 With I. I. Rabi, S. Millman, and P. Kusch. The molecular beam resonance method for measuring nuclear magnetic moments. Phys. Rev. 55:728. With J. M. B. Kellogg, I. I. Rabi, and N. F. Ramsey. The magnetic

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448 BIOGRAPHICAL MEMOIRS moments of the proton and deuteron. The radio frequency spec- trum of H2 in various magnetic fields. Phys. Rev. 56:728. 1940 With I. M. B. Kellogg, I. I. Rabi, and N. F. Ramsey. The electric quadrupole moment of the deuteron. Phys. Rev. 57:677-95. 1942 The nuclear spin and magnetic moment of K40. Phys. Rev. 61:270. 1947 With D. E. Nagle and R. S. Julian. The atomic hyperfine structure of hydrogen. Phys. Rev. 72:971. 1949 With L. Davis~and D. E. Nagle. Atomic beam magnetic resonance experiments with Na22, K40, CSI35 and Cs~37 Phys Rev 76:1068 1957 Today's science tomorrow's promise. Technol. Rev. (July) :501. With R. D. Haun. Stark effects in cesium-133 hyperfine structure. Phys. Rev. 107:107-9. 1961 Team approach to education. Am. f. Phys. 29:347-49. 1966 With O Cope. Medical Education Revisited: Report on the Endicott House Summer Study on Education. Philadelphia: Lippincott. Undergraduate education and atomic clocks. R. L. E. 1946+20, MIT. 1972 The common reader. Nat. Elem. Prin. 51:73-75. 1975 Testing in the schools: a help or a hindrance? Prospects 5:33-41. The trouble with IQ tests. Nat. Elem. Prin. 54:23-29.

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JERROLD R. ZACHARIAS 449 1980 The case of the missing scientists. Nat. Elem. Prin. 59:14-17. 1983 With M. Gordon and S. R. Davis. Common sense and nuclear peace. Bull. At. Sci. 39 (April).

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