Precision hfs of 126Cs(T1/2=1.63m) by ABMR

Abstract The hfs separation Δ ν of 126 Cs( T 1 / 2 = 1.63 m ) in the 6 s S 1 / 2 2 ground state was obtained in a precision measurement near zero magnetic field by means of atomic beam magnetic resonance with laser optical pumping on-line with the CERN-PSB-ISOLDE mass separator. The result, Δ ν = 3629.514 (0.001) MHz, corrects significantly a previous published value from a high-field experiment. With our result, the precision of the nuclear magnetic moment, μ ( Cs 126 ) ≈ 0.776 μ N , is now limited by the influence of extended nuclear structure on the hfs (the Bohr–Weisskopf effect).