The Hyperfine Structure of the Stable Isotopes of Indium

The atomic beams magnetic resonance method has been applied to the study of the h.f.s. of the metastable ²P3/2 state of both In¹¹³ and In¹¹⁵. It has been found that the separations of the energy levels at zero external magnetic field are completely described by the equation W=haC/2+hbC(C+1), where C=F(F+1)-I(I+1)-J(J+1), and a and b are the magnetic dipole and electric quadrupole interaction constants, respectively. No evidence has been found to indicate the existence of a nuclear moment of higher order than the quadrupole moment. These are the heaviest atoms in which a critical search for such moments has been made.The numerical values of the constants for In¹¹⁵ are: a¹¹⁵,=242.165±0.002 mc/sec.b¹¹⁵,=1.56098±0.00006 mc/sec. The ratio a¹¹⁵a¹¹³ has been determined by Hardy and Millman to be 1.00224±{}0.00010. From this value, and the results of our measurements, the numerical values of the constants for In¹¹³ are: a¹¹³,=241.624±0.024 mc/sec.b¹¹³,=1.53855±0.00015 mc/sec. where the uncertainties in a¹¹³ and b¹¹³ follow from the uncertainty in the ratio of the a's. The numerical values of the electric quadrupole moments are: Q¹¹⁵,=1.161×10^-24cm²Q¹¹³,=1.144×10^-24cm². It is seen from the ratios I¹¹⁵I¹¹³=1, a¹¹⁵a¹¹³=1.00224, b¹¹⁵b¹¹³=1.01146, that in these measurable nuclear properties In¹¹³ and In¹¹⁵ exhibit the greatest degree of similarity observed for any pair of isotopes of odd mass differing in mass by two units.