[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.
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.