Multiple coulomb excitation of γ-vibrational bands in 162Dy, 166Er, 168Er and 170Er

Abstract

The 2 γ and 4 γ states in 162Dy, 166Er, 168Er and 170Er have been Coulomb excited with 45–60 MeV 16O ions. Values of B( E2; 0 → 2 γ ) were determined and the angular correlations of the de-excitation γ-rays in coincidence with the backscattered particles have been analysed to yield E2/M1 mixing ratios for the 2 γ → 2 and 4 γ → 4 transitions. From the measured branching ratios for the decay of the 2 γ and 4 γ states, values of z 2, the spin-independent mixing parameter for the γ-vibrational band, were determined. Two additional states having spin and parity assignments 0 + and 4 + have been identified in 170Er at energies of 889 and 1124 keV, respectively.