<Dl> <Dd> V Yukawa (r) = − g 2 e − μ r r, (\ displaystyle V_ (\ text (Yukawa)) (r) = - g ^ (2) (\ frac (e ^ (- \ mu r)) (r)),) </Dd> </Dl> <Dd> V Yukawa (r) = − g 2 e − μ r r, (\ displaystyle V_ (\ text (Yukawa)) (r) = - g ^ (2) (\ frac (e ^ (- \ mu r)) (r)),) </Dd> <P> where g is a magnitude scaling constant, i.e., the amplitude of potential, μ (\ displaystyle \ mu) is the Yukawa particle mass, r is the radial distance to the particle . The potential is monotone increasing, implying that the force is always attractive . The constants are determined empirically . The Yukawa potential depends only on the distance between particles, r, hence it models a central force . </P> <P> Throughout the 1930s a group at Columbia University led by I.I. Rabi developed magnetic resonance techniques to determine the magnetic moments of nuclei . These measurements led to the discovery in 1939 that the deuteron also possessed an electric quadrupole moment . This electrical property of the deuteron had been interfering with the measurements by the Rabi group . The deuteron, composed of a proton and a neutron, is one of the simplest nuclear systems . The discovery meant that the physical shape of the deuteron was not symmetric, which provided valuable insight into the nature of the nuclear force binding nucleons . In particular, the result showed that the nuclear force was not a central force, but had a tensor character . Hans Bethe identified the discovery of the deuteron's quadrupole moment as one of the important events during the formative years of nuclear physics . </P>

Nuclear forces are charge independent and spin dependent