Mass number dependence of hexadecapole (Y42) excitation of the γ-vibrational band in proton inelastic scattering for 152⩽A⩽192

Abstract Inelastic scattering exciting the 2 + and 4 + members of the K π =2 + γ-vibrational band in 152, 154 Sm, 160 Gd, 164 Dy, 166, 168 Er, 176 Yb, 182, 184 W and 192 Os has been measured with 65 MeV polarized protons. The quadrupole ( Y 22 ) and hexadecapole ( Y 42 ) transition strengths to the γ-vibrational band have been extracted systematically for the first time. They show strong mass number dependences, which are explained qualitatively by a simple geometrical picture.