# Shape coexistence in light krypton isotopes

1 DAPNIA - Département d-Astrophysique, de physique des Particules, de physique Nucléaire et de l-Instrumentation Associée 2 CENBG - Centre d-Etudes Nucléaires de Bordeaux Gradignan 3 GANIL - Grand Accélérateur National d-Ions Lourds 4 IPNL - Institut de Physique Nucléaire de Lyon 5 LPSC - Laboratoire de Physique Subatomique et de Cosmologie 6 CSNSM - Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse

Abstract : Shape coexistence in the light krypton isotopes was studied in a series of experiments at GANIL using various experimental techniques. A new low-lying $0^+$ state, a so-called shape isomer, was found in delayed conversion-electron spectroscopy after fragmentation reactions. The systematics of such low-lying $0+^$ states suggests that the ground states of the isotopes $^{78}$Kr and $^{76}$Kr have prolate deformation, while states with prolate and oblate shape are practically degenerate and strongly mixed in $^{74}$Kr, and that the oblate configuration becomes the ground state in $^{72}$Kr. This scenario was tested in experiments performing low-energy Coulomb excitation of radioactive $^{76}$Kr and $^{74}$Kr beams from the SPIRAL facility. Both transitional and diagonal electromagnetic matrix elements were extracted from the observed $\gamma$-ray yields. The results find the prolate shape for the ground-state bands in $^{76}$Kr and $^{74}$Kr and an oblate deformation for the excited $2^{+} {2}$ state in $^{74}$Kr, confirming the proposed scenario of shape coexistence

Keywords : nuclear shape krypton nuclei with mass number 59 to 89 isotopes nuclear isomerism deformed nuclei nuclear fragmentation electron spectroscopy

Author: E. Clément - A. Görgen - E. Bouchez - A. Chatillon - W. Korten - Y. Le Coz - C. Theisen - C. Andreoiu F. Becker B. Blank - C. B

Source: https://hal.archives-ouvertes.fr/