FastE1transitions and evidence for octupole-octupole and quadrupole-octupole excitations inSm144

Abstract

The nucleus '~Sm has been studied with the (n, n'y) reaction and lifetimes of many states have been extracted from the observed Doppler shifts of the deexciting y rays. A large number of fast E1 transitions have been observed and have led to the identification of possible members of the octupole-octupole and the quadrupole-octupole multiplets.Substantial fragmentation of the twophonon octupole strength is indicated.

Coupled-channels analysis of the16O+208Pbfusion barrier distribution

“…At first, this result was puzzling in that there is both theoretical and experimental evidence for the presence of double-octupole phonon states in 144 Sm [43]. However, deviations from the pure harmonic vibration model are expected to occur and the assumption of vibrational harmonicity for the coupling in 144 Sm is not correct.…”

Two Phonon Excitations in Heavy Nuclei Studied in Photon Scattering Experiments

“…Another possibility is the coupling of the quadrupole with an octupole vibration creating a multiplet of five states with J" =1 -,2-, ... ,5-. The 1 -member of this multiplet has been identified in several nuclei but the information on the other states is still rather sparse [2,3,4].…”

Lifetime measurements of low-spin negative-parity levels in Gd160

“…The increasing level density with excitation energy and the proximity of the pairing gap complicate the identification of vibrations in deformed nuclei. Two-phonon octupole excitations have been observed in spherical nuclei of the rare-earth region -144 Sm [12], 146 Sm [13], 146 Gd [14], 147 Gd [15], and 148 Gd [16,17] -as has the combined two-phonon quadrupole-octupole vibrational mode (2 + ⊗ 3 − ) in nearly spherical nuclei -e.g., 144 Sm [12], 146 Sm [18], and 148 Gd [13]. A few cases have been suggested as two-phonon double-γ vibrations (K π = 4 + ) in 164 Dy [19], 166 Er [20], 168 Er [21][22][23], and (K π = 0 + ) in 166 Er [24].…”