'''Nuclear orientation''', in nuclear physics, is the directional ordering of an assembly of nuclear spins with respect to some axis in space.<ref>[http://encyclopedia2.thefreedictionary.com/nuclear+orientation Nuclear orientation], ''The Free Dictionary''.</ref><ref>[http://www.accessscience.com/abstract.aspx?id=459400 Nuclear orientation] {{Webarchive|url=https://web.archive.org/web/20110617073421/http://www.accessscience.com/abstract.aspx?id=459400 |date=2011-06-17 }}, ''[http://www.accessscience.com/ AccessScience]''.</ref> It is one of the nuclear spectroscopy methods.
A nuclear level with spin in a magnetic field will divide into magnetic sub-levels with an energy spacing.<ref name="nog">[http://www-nog.physics.ox.ac.uk/www/gen/gen.html General Idea of Nuclear Orientation], [http://www-nog.physics.ox.ac.uk/ Nuclear Orientation Group], University of Oxford, UK.</ref> The populations of these levels are determined by the Boltzmann distribution at a steady temperature and will essentially be equal. The exponential in the Boltzmann distribution should not be equal to 1 to obtain unequal populations. To achieve this, cooling to a temperature of around 10 millikelvin is needed. Typically, this is achieved by implanting the nuclei of interest into ferromagnetic hosts.
In the mid-1940s, Yevgeny Zavoisky developed electron paramagnetic resonance, eventually leading to the concept of nuclear orientation.<ref>B. Bleaney and O. V. Lounasmaa, [https://www.jstor.org/stable/3557722 Nuclear Orientation and Nuclear Cooling Experiments in Oxford and Helsinki. Part 2. Progress from 1945 to 1970]. ''Notes and Records of the Royal Society of London'', Volume 57, Number 3, pages 323–330, September 2003. Published by The Royal Society.</ref> In the early 1950s, Neville Robinson, Jim Daniels, and Michael Grace produced an example of nuclear orientation for the first time at the Clarendon Laboratory, University of Oxford.<ref>Nicholas Kurti, [https://www.independent.co.uk/news/people/obituary-neville-robinson-1354491.html Obituary: Neville Robinson]{{dead link|date=August 2021|bot=medic}}{{cbignore|bot=medic}}. ''The Independent'', 27 November 1996.</ref> There is now a Nuclear Orientation Group at Oxford.<ref name="nog" />
== Bibliography == * K. S. Krane, [https://doi.org/10.1007%2FBF02398283 Nuclear orientation and nuclear structure]. ''Hyperfine Interactions'', Volume 43, Numbers 1–4, pages 3–14, December, 1988. {{doi|10.1007/BF02398283}} * B. Bleaney, [https://www.jstor.org/stable/53459 Cross-relaxation and nuclear orientation in ytterbium vanadate]. ''Proceedings: Mathematical, Physical and Engineering Sciences'', Volume 455, Number 1988, pages 2835–2839, 8 August 1999. Published by The Royal Society. * B. Bleaney, [https://doi.org/10.1007%2FBF03162437 Dynamic nuclear polarization and nuclear orientation in terbium vanadate]. ''Applied Magnetic Resonance'', Volume 21, Number 1, pages 35–38, December, 1988. {{doi|10.1007/BF03162437}}
== See also == * Nuclear magnetic resonance * Mössbauer spectroscopy * Perturbed angular correlation
== References == {{reflist}}
Category:Nuclear physics Category:Nuclear magnetic resonance