High-spin spectroscopy of the Eu-142, Eu-143 and Eu-144 nuclei

High-spin level schemes of the Eu-142, Eu-143 and Eu-144 nuclei have been investigated by in-beam gamma-ray spectroscopic methods using the NORDBALL Compton-suppressed multi-detector array. The previously known schemes have been extended to considerably higher spin and excitation energy, up to I approximate to 30, E(x) greater than or equal to 9 MeV in Eu-142, I = 75/2 E(x) = 15.6 MeV in Eu-143 and I approximate to 40, E(x) greater than or equal to 16 MeV in Eu-144. The level schemes are very complicated, characteristic of spherical or slightly oblate nuclei. Also, long cascades of stretched E2 transitions have been observed in all three nuclei. Plunger and DSAM lifetime results demonstrate high collectivity values up to similar to 100 W.u. (up to similar to 200 W.u. in Eu-142) in, these E2 cascades and they are proposed to represent several crossing collective bands with the nucleus at triaxial shape of beta(2) approximate to 0.25 and gamma approximate to 30 degrees. Low parts of the level schemes have been discussed within the spherical shell model. Below 5.5 MeV excitation in Eu-144 and 3.5 MeV in Eu-143 practically all the observed levels are interpreted with shell model configurations of respectively two or four, and one or three quasiparticles.