ISOTOPE SHIFT AND HYPERFINE-STRUCTURE MEASUREMENTS AT THE AM-242F FISSION ISOMER

Istope shift and hyperfine structure measurements have been performed for the Am-242f fission isomer with target production rates of only a few per second. The method is based on resonance ionization spectrosco py (RIS) in a buffer gas cell with radioactive decay detection of the ionization process (RADRIS). A relative isotope shift ratio X(exp) = I S242f,241/IS243,241 = 41.7 +/- 0.9 has been measured for the 500.02 nm transition corresponding to a nuclear parameter Lambda(242f,241) = 5. 4 +/- 0.3 fm(2). The analysis of the quadrupole moment based on the de formed Fermi-model of the nuclear charge distribution including second order corrections results in Q(20) = 38.2 +/- 1.4((+0.4)(-0.8))(model ) e b. The measurement of the hyperfine structure splitting of the tra nsition at 466.28 nm yields a negative g-factor and a nuclear spin of I = 2 or I = 3.