Isotope shift measurement at ^244fAm *

Abstract

Optical isotope shift measurements have been performed at the ^244fAm fission isomers (T _1/2=1 ms) with low target production rates of 10/s employing resonance ionization spectroscopy in a buffer gas cell. The isotope shift ratio IS^244f,241/IS^243,241 = 42.0(9) has been measured at the 500.02 nm transition. A change in the nuclear mean charge radius $\delta \langle r^2 \rangle _{{\text{opt}}}^{{\text{224}}f,241}$ = 5.41(31) fm² and an intrinsic quadrupole moment $Q_{{\text{20}}}^{{\text{224}}f}$ = 34.4 eb have been deduced with the deformed Fermi model. The small difference of the nuclear parameter Λ^244f,242f = 0.069(21) fm² between the ^244fAm and ^242fAm fission isomers results in a change of the quadrupole moment $\delta Q_{{\text{20}}}^{{\text{224}}f,242f}$ eb only and demonstrates the stability of the superdeformation in the second potential minimum if two neutrons are removed.