Splitting the atom

After the work by Marie Curie and her daughter Irene established a new field of research in the radioactivity of elements, others carried out similar experiments to begin to understand the internal stmcture of the nucleus and a period of increased research occurred in the 1930s. At the Kaiser Wilhelm Institute in Berlin and the Niels Bohr Institute in Stockholm, a drama unfolded in 1938 that ushered in the atomic age. Lise Meitner was a petite, shy Austrian girl who made friends with a 

FIGURE 7.7 Lise Meitner (1878-1968) was an Austrian physicist who first described the splitting of a uranium nucleus as fission and Otto Hahn (1879-1968) who was awarded the 1944 Nobel Prize in chemistry for analyzing the elemental fragments of uranium fission. He missed the Nobel ceremony because at the time he was a prisoner of war in a British camp. Meitner was later recognized for her key role in the interpretation of Hahn s data when the United States awarded her the Fermi Award jointly with Hahn and his assistant Fritz Strassmann. Judging by her youthful appearance this was probably taken at the Kaiser Wilhelm Institute in Berlin in 1913. Details are given by David Bodanis in the historical novel E=mc.  

Since Kr is a gas, only Ba would show up in the analysis of the solids in the U target. It is important to note that this reaction produces more neutrons than are needed to start the reaction so a chain reaction is definitely possible in the presence of more 92 U. 

In the examples of nuclear reactions which follow we will focus on conservation of particles even though we know from Einstein s formula E = mc that small amounts of mass can be converted into enormous amounts of energy and we will use integers for particle numbers. In this way, we have to balance the isotope superscripts as well as the subscripts. Note in the fission of U, the number of (protons + neutrons) in the superscript adds up to 236 on both sides of the reaction and the number of protons in the subscripts adds up to 92 on both sides of the reaction. Here are a few nuclear reactions given in the Sasin and Sasin text [10,11] (by peimission)  

Emission of a proton, a process common to many elements from C to K 

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In 1938, Lise Meitner, Otto Hahn, and Fritz Strassmann realized that, by bombarding heavy atoms such as uranium with neutrons, they could split the atoms into smaller fragments in fission reactions, releasing huge amounts of energy. We can estimate the energy that would be released by using Einstein s equation, as we did in Example 17.5. 

Cathcart, Brian. The Fly in the Cathedral How a Group of Cambridge Scientists Won the International Race to Split the Atom. New York Farrar, Straus, and Giroux, 2004. 

In lanthanide complexes, the ligand field created by the surrounding ligands will split the atomic /-multiplets into several components. The latter are doubly degenerate (Kramers doublets (KDs)) for systems with odd number of electrons and non-degenerate (in the absence of symmetry) for systems with even number of electrons. 

This was just the start. In 1919 Rutherford found that alpha particles emitted from radium could chip protons from the nuclei of nitrogen atoms. This was something new. Radioactive elements decayed spontaneously into other elements because they were fundamentally unstable. But there was nothing unstable about nitrogen. Yet Rutherford had nevertheless managed to transmute it artificially. The newspapers found a catchy phrase for this feat splitting the atom . 

Today the number has reached 102 — the last ten man-made, produced by splitting the atoms of other elements. Within a short time, Element 103 will probably be discovered. 

While at Manchester. Rutherford produced the first human nuclear reaction with the disintegration of a non-radioactive atom, dislodging a single particle. He became famous as the man who split the atom. In 1919, Rutherford succeeded J.J. Thomson as Cavendish Professor of Physics at Cambridge. He was a leader of a research team encouraging others in the investigation of the nucleus. 

Splitting the atom, many new elements were discovered by Seaborg. 

Splitting the atom, Seaborg discovered many new elements. 

Richardson, Hazel, and Scoular Anderson. How to Split the Atom. Franklin Watts, 2001. 

Nuclear fission—"Splitting the atom." A nuclear reaction in which an atomic nucleus splits into fragments with the release of energy, including radioactivity. 

Rutherford s work has made him known as the father of nuclear physics with his research on radioactivity (alpha and beta particles and protons, which he named), and he was the first to describe the concepts of half-life and decay constant. He showed that elements such as uranium transmute (become different elements) through radioactive decay, and he was the first to observe nuclear reactions (split the atom in 1917). In 1908 he received the Nobel Prize in chemistry for his investigations into the disintegration of the elements, and the chemistry of radioactive substances. He was president of the Royal Society (1926-30) and of the Institute of Physics (1931-33) and was decorated with the Order of Merit (1925). He became Lord Rutherford in 1931. 

Urf being the selected radio frequency and H the homogeneous field applied. This original setup was then widely used for the determination of the magnetic and quadrupolar hyperfine structure (hfs) constants A and B. Hereby one has to consider that the additional magnetic field further splits the atomic energy levels now characterized by F into (2F + 1) sublevels and mixes states of the same Mp but different F values. A Zeeman term has therefore to be added to the hyperfine Hamiltonian according to... 

In 1979 Reines, Sobel and Pasierb made new neutrino measurements with a detector containing heavy water so that the neutrinos would either split the atom into a proton and a neutron, or convert it into two neutrons. Both reactions would only be sensitive to the 1 by measuring the neutron yield, the number of p s could be calculated and compared to the known p. flux from the reactor. The two different decays could be followed by measuring the time delays between neutron capture and 7 emission (see Ch. 8). The ratio of these two measurements was only 0.43 0.17, i.e. half of that expected. The explanation proposed was that the two types of neutrinos interchange, or oscillate between the p and the p states, thus only 50% of the expected number would be observed. 

The discovery of radioactivity led to the eventual realization that the atom, which took its name from the idea that it was indivisible, could in fact be subdivided into more basic particles the proton, neutron, and electron. Rutherford was the first to try to split the atom, something he achieved by using one of the newly discovered products of radioactive decay, the alpha particle. 

Thus, the ultimate power of the comic book presentation of the early atomic age probably lay less with the factual publications than with its skill at storytelling. And, as we are just now beginning to realize, whoever tells the stories controls the culture. Dagwood Splits the Atom to the contrary, comic book writers and artists had far more influence when they wove the atomic messages into thrilling tales of adventure. 

Cover of The Atomics 1 (AAA Pop Comics, January 2000). Like most nuclear-themed comic book heroes, the more recent creations, such as the characters in The Atomics, cannot convey the multifaceted implications that flowed from splitting the atom. Created, written, and drawn by Michael Allred colors by Laura Allred. 

Joe Musial, Dogwood Splits the Atom (1949) (King Features). Such comic book depictions were much more sophisticated than the nuclear songs found in the coimtry music of the era. See Charles Wolfe, "Nuclear Country The Atomic Bomb in Coimtry Music," Journal of Country Music 6 (January 1978) 4-22. "Joe Musial, 72, Drew Katzen-jammer Kids," New York Times, June 8,1977, 62. 

Several types of atom interferometers have been realized that use various light-field configurations to split and recombine atomic beams. The main requirement for the light field is that it should split the atomic wave by the maximum possible angle without multiple scattering of the beam. So far, researchers have failed to devise an ideal laser atomic-beam splitter that would be comparable with the semitransparent mirrors in optical interferometry. 

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