Nuclear orientation

Nuclear orientation, in nuclear physics, is the directional ordering of an assembly of nuclear spins with respect to some axis in space.[1][2] 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.[3] 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.[4] 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.[5] There is now a Nuclear Orientation Group at Oxford.[3]