The Nuclear Spin of Caesium

The spin of the caesium nucleus has been measured by the deflection of a beam of atoms in a weak inhomogeneous magnetic field. The method utilizes the fact that the magnetic moment of the atoms in some of the magnetic levels vanishes at certain values of the magnetic field. An examination of the variation of the intensity at the center of the pattern yields distinct maxima at these fields. From the number and position of these maxima, the spin can be uniquely deduced. If the magnetic field is known, the hyperfine structure separation can be deduced with accuracy. The nuclear spin of Cs was found to be $\frac{7}{2}$ in units of $\frac{h}{2\pi }$ and the hyperfine structure separation for the normal state was found to be 0.295±0.01 ${\mathrm{cm}}^{-1\mathrm{}}$.