Felix Bloch Papers
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Charles Hard Townes (1915–2015)
ARTICLE-IN-A-BOX Charles Hard Townes (1915–2015) C H Townes shared the Nobel Prize in 1964 for the concept of the laser and the earlier realization of the concept at microwave frequencies, called the maser. He passed away in January of this year, six months short of his hundredth birthday. A cursory look at the archives shows a paper as late as 2011 – ‘The Dust Distribution Immediately Surrounding V Hydrae’, a contribution to infrared astronomy. To get a feel for the range in time and field, his 1936 masters thesis was based on repairing a non-functional van de Graaf accelerator at Duke University in 1936! For his PhD at the California Institute of Technology, he measured the spin of the nucleus of carbon-13 using isotope separation and high resolution spectroscopy. Smythe, his thesis supervisor was writing a comprehensive text on electromagnetism, and Townes solved every problem in it – it must have stood him in good stead in what followed. In 1939, even a star student like him did not get an academic job. The industrial job he took set him on his lifetime course. This was at the legendary Bell Telephone Laboratories, the research wing of AT&T, the company which set up and ran the first – and then the best – telephone system in the world. He was initially given a lot of freedom to work with different research groups. During the Second World War, he worked in a group developing a radar based system for guiding bombs. But his goal was always physics research. After the War, Bell Labs, somewhat reluctantly, let him pursue microwave spectroscopy, on the basis of a technical report he wrote suggesting that molecules might serve as circuit elements at high frequencies which were important for communication. -
Edward Mills Purcell (1912–1997)
ARTICLE-IN-A-BOX Edward Mills Purcell (1912–1997) Edward Purcell grew up in a small town in the state of Illinois, USA. The telephone equipment which his father worked with professionally was an early inspiration. His first degree was thus in electrical engineering, from Purdue University in 1933. But it was in this period that he realized his true calling – physics. After a year in Germany – almost mandatory then for a young American interested in physics! – he enrolled in Harvard for a physics degree. His thesis quickly led to working on the Harvard cyclotron, building a feedback system to keep the radio frequency tuned to the right value for maximum acceleration. The story of how the Manhattan project brought together many of the best physicists to build the atom bomb has been told many times. Not so well-known but equally fascinating is the story of radar, first in Britain and then in the US. The MIT radiation laboratory was charged with developing better and better radar for use against enemy aircraft, which meant going to shorter and shorter wavelengths and detecting progressively weaker signals. This seems to have been a crucial formative period in Purcell’s life. His coauthors on the magnetic resonance paper, Torrey and Pound, were both from this lab. I I Rabi, the physicist who won the 1944 Nobel Prize for measuring nuclear magnetic moments by resonance methods in molecular beams, was the head of the lab and a major influence on Purcell. Interestingly, Felix Bloch (see article on p.956 in this issue) was at the nearby Radio Research lab but it appears that the two did not interact much. -
Wolfgang Pauli Niels Bohr Paul Dirac Max Planck Richard Feynman
Wolfgang Pauli Niels Bohr Paul Dirac Max Planck Richard Feynman Louis de Broglie Norman Ramsey Willis Lamb Otto Stern Werner Heisenberg Walther Gerlach Ernest Rutherford Satyendranath Bose Max Born Erwin Schrödinger Eugene Wigner Arnold Sommerfeld Julian Schwinger David Bohm Enrico Fermi Albert Einstein Where discovery meets practice Center for Integrated Quantum Science and Technology IQ ST in Baden-Württemberg . Introduction “But I do not wish to be forced into abandoning strict These two quotes by Albert Einstein not only express his well more securely, develop new types of computer or construct highly causality without having defended it quite differently known aversion to quantum theory, they also come from two quite accurate measuring equipment. than I have so far. The idea that an electron exposed to a different periods of his life. The first is from a letter dated 19 April Thus quantum theory extends beyond the field of physics into other 1924 to Max Born regarding the latter’s statistical interpretation of areas, e.g. mathematics, engineering, chemistry, and even biology. beam freely chooses the moment and direction in which quantum mechanics. The second is from Einstein’s last lecture as Let us look at a few examples which illustrate this. The field of crypt it wants to move is unbearable to me. If that is the case, part of a series of classes by the American physicist John Archibald ography uses number theory, which constitutes a subdiscipline of then I would rather be a cobbler or a casino employee Wheeler in 1954 at Princeton. pure mathematics. Producing a quantum computer with new types than a physicist.” The realization that, in the quantum world, objects only exist when of gates on the basis of the superposition principle from quantum they are measured – and this is what is behind the moon/mouse mechanics requires the involvement of engineering. -
Bringing out the Dead Alison Abbott Reviews the Story of How a DNA Forensics Team Cracked a Grisly Puzzle
BOOKS & ARTS COMMENT DADO RUVIC/REUTERS/CORBIS DADO A forensics specialist from the International Commission on Missing Persons examines human remains from a mass grave in Tomašica, Bosnia and Herzegovina. FORENSIC SCIENCE Bringing out the dead Alison Abbott reviews the story of how a DNA forensics team cracked a grisly puzzle. uring nine sweltering days in July Bosnia’s Million Bones tells the story of how locating, storing, pre- 1995, Bosnian Serb soldiers slaugh- innovative DNA forensic science solved the paring and analysing tered about 7,000 Muslim men and grisly conundrum of identifying each bone the million or more Dboys from Srebrenica in Bosnia. They took so that grieving families might find some bones. It was in large them to several different locations and shot closure. part possible because them, or blew them up with hand grenades. This is an important book: it illustrates the during those fate- They then scooped up the bodies with bull- unspeakable horrors of a complex war whose ful days in July 1995, dozers and heavy earth-moving equipment, causes have always been hard for outsiders to aerial reconnais- and dumped them into mass graves. comprehend. The author, a British journalist, sance missions by the Bosnia’s Million It was the single most inhuman massacre has the advantage of on-the-ground knowl- Bones: Solving the United States and the of the Bosnian war, which erupted after the edge of the war and of the International World’s Greatest North Atlantic Treaty break-up of Yugoslavia and lasted from 1992 Commission on Missing Persons (ICMP), an Forensic Puzzle Organization had to 1995, leaving some 100,000 dead. -
I. I. Rabi Papers [Finding Aid]. Library of Congress. [PDF Rendered Tue Apr
I. I. Rabi Papers A Finding Aid to the Collection in the Library of Congress Manuscript Division, Library of Congress Washington, D.C. 1992 Revised 2010 March Contact information: http://hdl.loc.gov/loc.mss/mss.contact Additional search options available at: http://hdl.loc.gov/loc.mss/eadmss.ms998009 LC Online Catalog record: http://lccn.loc.gov/mm89076467 Prepared by Joseph Sullivan with the assistance of Kathleen A. Kelly and John R. Monagle Collection Summary Title: I. I. Rabi Papers Span Dates: 1899-1989 Bulk Dates: (bulk 1945-1968) ID No.: MSS76467 Creator: Rabi, I. I. (Isador Isaac), 1898- Extent: 41,500 items ; 105 cartons plus 1 oversize plus 4 classified ; 42 linear feet Language: Collection material in English Location: Manuscript Division, Library of Congress, Washington, D.C. Summary: Physicist and educator. The collection documents Rabi's research in physics, particularly in the fields of radar and nuclear energy, leading to the development of lasers, atomic clocks, and magnetic resonance imaging (MRI) and to his 1944 Nobel Prize in physics; his work as a consultant to the atomic bomb project at Los Alamos Scientific Laboratory and as an advisor on science policy to the United States government, the United Nations, and the North Atlantic Treaty Organization during and after World War II; and his studies, research, and professorships in physics chiefly at Columbia University and also at Massachusetts Institute of Technology. Selected Search Terms The following terms have been used to index the description of this collection in the Library's online catalog. They are grouped by name of person or organization, by subject or location, and by occupation and listed alphabetically therein. -
Turning Point in the Development of Quantum Mechanics and the Early Years of the Mossbauer Effect*
Fermi National Accelerator Laboratory FERMILAB-Conf-76/87-THY October 1976 A TURNING POINT IN THE DEVELOPMENT OF QUANTUM MECHANICS AND THE EARLY YEARS OF THE MOSSBAUER EFFECT* Harry J. Lipkin' Weizmann Institute of Science, Rehovot, Israel Argonne National Laboratory, Argonne, Illinois 60^39 Fermi National Accelerator Laboratory"; Batavia, Illinois 60S10 It is interesting to hear about the exciting early days recalled by Professors Wigner and Wick. I learned quantum theory at a later period, which might be called a turning point in its development, when the general attitude toward quantum mechanics and the study of physics was very different from what it is today. As an undergraduate student in electrical engineering in 19^0 in the United States I found a certain disagreement between the faculty and the students about the "relevance'- of the curriculum. Students thought a k-year course in electrical engineering should include more electronics than a one-semester 3-hour course. But the establishment emphasized the study of power machinery and power transmission because 95'/° of their graduates would eventually get jobs in power. Electronics, they said, was fun for students who were radio hams but useless on the job market. Students at that time did not have today's attitudes and did not stage massive demonstrations and protests against the curriculum. Instead a few of us who wished to learn more interesting things satisfied all the requirements of the engineering school and spent as much extra time as possible listening to fascinating courses in the physics building. There we had the opportunity to listen to two recently-arrived Europeans, Bruno Rossi and Hans Bethe. -
Laser Spectroscopy to Resolve Hyperfine Structure of Rubidium
Laser spectroscopy to resolve hyperfine structure of rubidium Hannah Saddler, Adam Egbert, and Will Weigand (Dated: 12 November 2015) This experiment had two main goals: to create an absorption spectrum for rubidium using the technique of absorption spectroscopy and to resolve the hyperfine structures for the two rubidium isotopes using saturation absorption spectroscopy. The absorption spectrum was used to determine the frequency difference between the ground state and first excited state for both isotopes. The calculated frequency difference was 6950 MHz ± 90 MHz for rubidium 87 and 3060 MHz ± 60 MHz for rubidium 85. Both values agree with the literature values. The hyperfine structure for rubidium 87 was able to be resolved using this experimental setup. The energy differences were determined to be 260 MHz ± 10 MHz and 150 MHz ± 10 Mhz MHz. The hyperfine structure for rubidium 85 was unable to be resolved using this experimental setup. Additionally the theory of doppler broadening was used to make measurements of the full width half maximum. These values were used to calculate a temperature of 310K ± 40 K which makes sense because the experiments were performed at room temperature. I. INTRODUCTION in the theory section and how they were manipulated and used to derive the results from the recorded data. Addi- tionally there is an explanation of experimental error and The era of modern spectroscopy began with the in- uncertainty associated the results. Section V is a conclu- vention of the laser. The word laser was originally an sion that ties the results of the experiment we performed acronym that stood for light amplification by stimulated to the usefulness of the technique of laser spectroscopy. -
Laser Spectroscopy Experiments
Hyperfine Spectrum of Rubidium: laser spectroscopy experiments Physics 480W (Dated: Sp19 Paper #4) I. OBJECTIVES FOR THESE EXPERIMENTS We wish to use the technique of absorption spec- troscopy to probe and detect the energy level structure of atomic Rubidium, Rb I, whose ground state is split by a tiny amount on account of nuclear magnetism. In effect, the spectroscopy we do today tells us about nuclear prop- erties and so combines atomic and nuclear physics. The main result of this experiment, the 4th of the semester, is to 1. measure the hyperfine splitting for each isotope, and compare with accepted values, with the fol- lowing details in mind: (a) what is the hyperfine splitting of the ground 2 state, S1=2 term? Do we need saturation- absorption techniques for this? (b) what are the hyperfine splittings of the ex- 2 cited state, P3=2 term, that can be reached with a nominal wavelength of 780nm from the ground state? Here we need saturation- absorption techniques to perform sub-Doppler FIG. 1. Note the four 'blobs'. Why are there four? Which spectroscopy, certainly. Help the reader un- 85 are associated with Rb37, and so on. If all goes swimm- derstand what is entailed in the technique, ingly, we'll get an absorption spectrum that looks much line both experimentally and theoretically. You the figure below the setup. The etalon data will be needed to will need to explain what `saturation' means. make the abscissa something proportional to frequency. The The saturation intensity is an important fig- accepted value of the gap between the 2 outermost dips is ure of merit. -
Appendix E Nobel Prizes in Nuclear Science
Nuclear Science—A Guide to the Nuclear Science Wall Chart ©2018 Contemporary Physics Education Project (CPEP) Appendix E Nobel Prizes in Nuclear Science Many Nobel Prizes have been awarded for nuclear research and instrumentation. The field has spun off: particle physics, nuclear astrophysics, nuclear power reactors, nuclear medicine, and nuclear weapons. Understanding how the nucleus works and applying that knowledge to technology has been one of the most significant accomplishments of twentieth century scientific research. Each prize was awarded for physics unless otherwise noted. Name(s) Discovery Year Henri Becquerel, Pierre Discovered spontaneous radioactivity 1903 Curie, and Marie Curie Ernest Rutherford Work on the disintegration of the elements and 1908 chemistry of radioactive elements (chem) Marie Curie Discovery of radium and polonium 1911 (chem) Frederick Soddy Work on chemistry of radioactive substances 1921 including the origin and nature of radioactive (chem) isotopes Francis Aston Discovery of isotopes in many non-radioactive 1922 elements, also enunciated the whole-number rule of (chem) atomic masses Charles Wilson Development of the cloud chamber for detecting 1927 charged particles Harold Urey Discovery of heavy hydrogen (deuterium) 1934 (chem) Frederic Joliot and Synthesis of several new radioactive elements 1935 Irene Joliot-Curie (chem) James Chadwick Discovery of the neutron 1935 Carl David Anderson Discovery of the positron 1936 Enrico Fermi New radioactive elements produced by neutron 1938 irradiation Ernest Lawrence -
Nobel Prize Physicists Meet at Lindau
From 28 June to 2 July 1971 the German island town of Lindau in Nobel Prize Physicists Lake Constance close to the Austrian and Swiss borders was host to a gathering of illustrious men of meet at Lindau science when, for the 21st time, Nobel Laureates held their reunion there. The success of the first Lindau reunion (1951) of Nobel Prize win ners in medicine had inspired the organizers to invite the chemists and W. S. Newman the physicists in turn in subsequent years. After the first three-year cycle the United Kingdom, and an audience the dates of historical events. These it was decided to let students and of more than 500 from 8 countries deviations in the radiocarbon time young scientists also attend the daily filled the elegant Stadttheater. scale are due to changes in incident meetings so they could encounter The programme consisted of a num cosmic radiation (producing the these eminent men on an informal ber of lectures in the mornings, two carbon isotopes) brought about by and personal level. For the Nobel social functions, a platform dis variations in the geomagnetic field. Laureates too the Lindau gatherings cussion, an informal reunion between Thus chemistry may reveal man soon became an agreeable occasion students and Nobel Laureates and, kind’s remote past whereas its long for making or renewing acquain on the last day, the traditional term future could well be shaped by tances with their contemporaries, un steamer excursion on Lake Cons the developments mentioned by trammelled by the formalities of the tance to the island of Mainau belong Mössbauer, viz. -
The Concept of the Photon—Revisited
The concept of the photon—revisited Ashok Muthukrishnan,1 Marlan O. Scully,1,2 and M. Suhail Zubairy1,3 1Institute for Quantum Studies and Department of Physics, Texas A&M University, College Station, TX 77843 2Departments of Chemistry and Aerospace and Mechanical Engineering, Princeton University, Princeton, NJ 08544 3Department of Electronics, Quaid-i-Azam University, Islamabad, Pakistan The photon concept is one of the most debated issues in the history of physical science. Some thirty years ago, we published an article in Physics Today entitled “The Concept of the Photon,”1 in which we described the “photon” as a classical electromagnetic field plus the fluctuations associated with the vacuum. However, subsequent developments required us to envision the photon as an intrinsically quantum mechanical entity, whose basic physics is much deeper than can be explained by the simple ‘classical wave plus vacuum fluctuations’ picture. These ideas and the extensions of our conceptual understanding are discussed in detail in our recent quantum optics book.2 In this article we revisit the photon concept based on examples from these sources and more. © 2003 Optical Society of America OCIS codes: 270.0270, 260.0260. he “photon” is a quintessentially twentieth-century con- on are vacuum fluctuations (as in our earlier article1), and as- Tcept, intimately tied to the birth of quantum mechanics pects of many-particle correlations (as in our recent book2). and quantum electrodynamics. However, the root of the idea Examples of the first are spontaneous emission, Lamb shift, may be said to be much older, as old as the historical debate and the scattering of atoms off the vacuum field at the en- on the nature of light itself – whether it is a wave or a particle trance to a micromaser. -
Heisenberg's Visit to Niels Bohr in 1941 and the Bohr Letters
Klaus Gottstein Max-Planck-Institut für Physik (Werner-Heisenberg-Institut) Föhringer Ring 6 D-80805 Munich, Germany 26 February, 2002 New insights? Heisenberg’s visit to Niels Bohr in 1941 and the Bohr letters1 The documents recently released by the Niels Bohr Archive do not, in an unambiguous way, solve the enigma of what happened during the critical brief discussion between Bohr and Heisenberg in 1941 which so upset Bohr and made Heisenberg so desperate. But they are interesting, they show what Bohr remembered 15 years later. What Heisenberg remembered was already described by him in his memoirs “Der Teil und das Ganze”. The two descriptions are complementary, they are not incompatible. The two famous physicists, as Hans Bethe called it recently, just talked past each other, starting from different assumptions. They did not finish their conversation. Bohr broke it off before Heisenberg had a chance to complete his intended mission. Heisenberg and Bohr had not seen each other since the beginning of the war in 1939. In the meantime, Heisenberg and some other German physicists had been drafted by Army Ordnance to explore the feasibility of a nuclear bomb which, after the discovery of fission and of the chain reaction, could not be ruled out. How real was this theoretical possibility? By 1941 Heisenberg, after two years of intense theoretical and experimental investigations by the drafted group known as the “Uranium Club”, had reached the conclusion that the construction of a nuclear bomb would be feasible in principle, but technically and economically very difficult. He knew in principle how it could be done, by Uranium isotope separation or by Plutonium production in reactors, but both ways would take many years and would be beyond the means of Germany in time of war, and probably also beyond the means of Germany’s adversaries.