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The Coulomb excitation measurements for the 23~ nucleus with 328, 84Kr and 142Nd projectiles are presented. The use of different projectiles allowed us to get information in the ground-state band and side bands. The energy spectrum of the ground-state band and of the lowest negative-parity band have been investigated up to the spin value I=24 + and I=19-(21), respectively. Five side bands (K~=0+,2+,2~, 1-,2-) were observed also. The branching ratios for a large number of transitions in the spin region I< 10 for ~= + l and 1<9 for re=-1 are analysed. The full set of experimental data contains information on the mixing of the adiabatic states and on the nuclear response to the electromagnetic field of ;:-radiation. It is shown that the experimental data may be explained taking into account the coupling of the ground-/3-and two 7-bands and also of the K~= 0-, 1-and 2-negative-parity bands. An enhancement of the transitions from the ~-to the/~-band in respect to the transitions from the 7 to the ground band and from the /~-to the ground band is reported. The mixing of the negative-parity bands is found to be typical for the alignment of the octupole-vibrational angular momentum. The strong spin dependence of the intrinsic matrix elements of the electric-dipole operator follows from the branching ratios of inter-and intra-band transitions from the K s=0 states.

Les transitions γ dans 223Ra ont été étudiées à l'aide de diodes Ge-Li en faisant appel à différents procédés de purification et de mesure afin de minimiser l'importance des six descendants radioactifs. A peu près 180 transitions parmi celles observées ont pu être placées dans le schéma de niveaux

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A thorough examination of the level structure of 223Ra provides evidence that leads to an extensive re-evaluation of spin assignments and hence band structure. Altogether six bands corresponding to three parity-coupled pairs are identified and the interpretation of the data suggests that this N = 135 nucleus may possess an octupole deformation.Results from a-y and y-y directional correlations and y-ray directional distribution measurements were combined and, together with internal conversion coefficient (ICC) data, give unique spin-parity assignments to most levels. A continuously purified source was used to make unambiguous y-ray assignments. Level half-lives were obtained from recoil distance and Doppler methods.The results show that the ground state is 3/2+. Parity doublets were identified as {3/2+(0 keV), 3/2-(50.1 keV)}, {1/2+(286.1 keV), 1/2-(350.5 keV)} and {5/2+(324.8 keV), 5/2-(369.3 keV)}. The multipole mixing ratios of many of the stronger y-ray transitions were determined and also the amplitudes and relative phases of the angular momentum components carried by the a decays.The band structure is interpreted within the framework of calculations using the Strutinski shell-correction method with a single-particle level scheme obtained with a Woods-Saxon mean field. The minimisation procedure for the total energy is achieved in a multideformation space including higher-order multipolarity deformations up to I. = 7. The importance of higher-order multipolarity deformation parameters is underlined.