The nuclear physics is that part of the field of physics that deals with the structure and behavior of atomic nuclei busy. While atomic physics deals with the physics of the atomic shell , the subject of nuclear physics is the elucidation of the nuclear structure , i.e. the details of the structure of the atomic nucleus. For this purpose, for example, spontaneous transformations of the nuclei ( radioactivity ), scattering processes on nuclei and reactions with nuclei are examined.
The high-energy physics and particle physics have formed from nuclear physics out and therefore were previously counted with her; the actual nuclear physics was then sometimes referred to as low- energy nuclear physics to differentiate . The reactor physics grew out of nuclear physics out.
The technologies based on nuclear fission (see nuclear technology ) for the use of nuclear energy and for weapons purposes have developed from certain research results in nuclear physics. But it is misleading to call this technical-economic-political area “the nuclear physics”.
Nuclear physics is carried out both theoretically and experimentally. Your most important theoretical aid is quantum mechanics . Experimental tools are e.g. B. particle detectors and radiation detectors , particle accelerators and vacuum technology .
The task of “pure” nuclear physics in the sense of basic research is to elucidate and explain the nuclear structure , i.e. the details of the structure of the atomic nuclei.
From the study of radioactivity and reactions with nuclei, many applications have developed, for example
- Energy generation from nuclear reactions using nuclear reactors and nuclear fusion reactors ,
- medical diagnostic and therapeutic procedures ( e.g. scintigraphy , brachytherapy ), collectively referred to as nuclear medicine ,
- chemical applications in radiochemistry or nuclear chemistry ,
- Procedure for preventive damage detection in pipelines using gamma radiation ,
- Production of material surfaces with special properties by means of ion implantation ,
- Auxiliary methods for other research areas such as radiocarbon dating in archeology or cosmochemistry .
Typical orders of magnitude in the area of atomic nuclei and nuclear processes are
The building blocks of the nuclei are the nucleons : neutrons and protons . The number Z of protons in a nucleus is equal to the number of electrons in the neutral atom. Z determines the chemical properties of the atoms and is therefore called the atomic number (or, based on the atomic nucleus, also the atomic number). The mass of the atomic nucleus is determined by the number A of all nucleons and is therefore also called the mass number . As you can see, the neutron number N = A - Z . Types of atoms with the same atomic number but different numbers of neutrons are called isotopes of the respective element. The physical properties of the nucleus depend on both the atomic number and the neutron number, the chemical properties (almost) only on the atomic number.
When describing nuclear reactions and scattering processes, the term cross-section is important. The cross-section for a certain process is a measure of the probability that this process will occur in individual cases.
Antoine Henri Becquerel , Pierre Curie and Marie Curie received the 1903 Nobel Prize in Physics for their experiments on radioactivity, which could be described as the historic beginning of modern nuclear research .
The Rutherford scattering experiment , in which alpha particles are scattered on gold foil, by Geiger , Marsden and Rutherford in 1909 marks a turning point in the idea of the structure of atoms. Rutherford's interpretation of the results led to the idea of the atomic nucleus . Almost the entire mass of the atom is united in the nucleus, but it only takes up a very small proportion of the volume of the atom.
The understanding of the binding energy of atomic nuclei, first expressed semi-empirically in 1935 in the Bethe-Weizsäcker formula , represented a decisive advance. The basis for the formula was the droplet model of the atomic nucleus (Bohr 1936). With the help of the Bethe-Weizsäcker formula it could be shown that energy is released in certain nuclear fusions as well as in certain nuclear fission . The droplet model is capable of z. B. to explain nuclear fission well.
A quantum mechanical description of the nucleus structure, which can explain the stability of the nuclei, which changes systematically with atomic and mass numbers, was only found later with the shell model (Wigner, Goeppert-Mayer and Jensen 1949). An important scientific journal in this field is Nuclear Physics .
Otto Hahn and his assistant Fritz Straßmann discovered in December 1938 that irradiation with neutrons split uranium nuclei (induced nuclear fission ). It was later demonstrated that a large amount of energy and further neutrons are released during this process, so that a fission chain reaction and thus the release of technically usable amounts of energy is possible in a short time, i.e. at high power . Research into the use of this energy for civil or military purposes then began, roughly at the same time as the Second World War . In Germany, among others, Carl Friedrich von Weizsäcker and Werner Heisenberg worked on the development of a nuclear reactor ; the possibility of a nuclear weapon was seen, but not seriously pursued, because the foreseeable development period seemed too long for the ruling war. In Los Alamos , the physicists Enrico Fermi , Hans Bethe , Richard Feynman , Edward Teller , Felix Bloch and others conducted research in the Manhattan Project under the direction of Robert Oppenheimer . Although this project served the development of weapons from the beginning, its findings also led to the construction of the first nuclear reactors used for energy generation.
Hardly any other area of physics has fueled public discussion more because of its ambivalence between peaceful and destructive use: for critics of progress, nuclear physics was Pandora's box , and for those who believe in progress, it was one of the most useful discoveries of the 20th century. Nuclear fission technology was the trigger for a new ethics of science ( Hans Jonas , Carl Friedrich von Weizsäcker ). The political debate about the sensible and responsible use of nuclear energy continues to this day in the debate about Germany's nuclear phase-out .
Eminent nuclear physicists
- Aage Niels Bohr (1922–2009), Danish physicist; Nobel Prize in Physics 1975 (theory of the collective motion of atomic nuclei), son of Niels Bohr
- Harriet Brooks (1876–1933), Canadian nuclear physicist, radioactivity , radioactive recoil
- James Chadwick (1891–1974), English physicist; Nobel Prize in Physics 1935 (discovery of the neutron ), development of the atomic bomb, Manhattan project
- John Douglas Cockcroft (1897–1967), English nuclear physicist; Nobel Prize in Physics 1951 (atomic nucleus conversion by accelerated particles), nuclear reactions , Cockcroft-Walton accelerator
- Klaus Fuchs (1911–1988), German-British nuclear physicist; Manhattan project , nuclear spy
- Otto Hahn (1879–1968), German chemist; Pioneer of radiochemistry , u. a. Discoverer of nuclear isomerism (uranium Z) and nuclear fission of uranium (Nobel Prize in Chemistry 1944). He is considered the "father of nuclear chemistry"
- Igor Kurchatov (1903–1960), Russian nuclear physicist
- Heinz Maier-Leibnitz (1911–2000) physicist and President of the German Research Foundation .
- Lise Meitner (1878–1968), Austrian physicist; (first physical-theoretical interpretation of nuclear fission, together with her nephew Otto Robert Frisch )
- Juri Zolakowitsch Oganesjan (* 1933), Russian nuclear physicist, co-discoverer of heavy elements
- Ernest Walton (1903–1995), Irish experimental physicist, Nobel Prize in Physics 1951, high-voltage cascade Cockcroft-Walton accelerator , first artificially initiated nuclear reaction
- Carl Friedrich Freiherr von Weizsäcker (1912–2007), German nuclear physicist, philosopher and peace researcher, Bethe-Weizsäcker cycle , Bethe-Weizsäcker formula , patents on the atomic bomb, Göttingen eighteen
- Document server for nuclear physics with 360,000 full text documents and 800,000 entries
- National Nuclear Data Center extensive homepage of the Brookhaven National Laboratory on various aspects of nuclear physics (including "Nuclear Wallet Cards")
- Experiments and exercises on nuclear physics at student level ( LEIFI )