The hfs of ${\mathrm{Cr}}^{53}$ has been investigated by the atomic-beam magnetic-resonance technique. The atoms were detected with an electron-bombardment universal detector. Novel counting techniques made possible observation of resonances for which the signal-to-background ratio was 0.0002. The magnetic-dipole hyperfine-interaction constant was measured to be $a=\pm (82.5985\mathrm{}\pm 0.0015)$ Mc/sec and the electric-quadrupole hyperfine-interaction constant was found to be consistent with $b=0\mathrm{}$. These results are compared with the theory. From the measured value of $a$, the average magnetic field at the nucleus is calculated to be 1.03×${10}^6$ G within about 1%.

• Received 18 July 1963

DOI:https://doi.org/10.1103/PhysRev.132.2128