This process was used to develop magnetic resonance imaging (MRI) and nuclear magnetic resonance spectroscopy (NMRS) technology.
It is also being used to develop nuclear magnetic resonance quantum computers.
The first observation of electron-spin resonance was in 1944 by Y. K. Zavosky, a Soviet physicist then teaching at Kazan State University (now Kazan Federal University).
Nuclear magnetic resonance was first observed in 1946 in the US by a team led by Felix Bloch at the same time as a separate team led by Edward Mills Purcell, the two of whom would later be the 1952 Nobel Laureates in Physics.
Alternatively, we can set up an experiment in which the system's behavior depends on the energy level.