Une description cohérente des noyaux déformés a l'aide d'une méthode de moindres carrés non linéaire appliquée a l'inversion de la matrice des énergies

The asymmetric rotator model applied to odd-mass Iridium isotopes

“…Further it is interesting, at this point, to remember the situation one had [20][21][22] for the same kind of approach in an axial nucleus where one couples two rotational bands with K= 1/2 and K =3/2 built on two intrinsic states. The corresponding matrix elements of the Hamiltonian H a with axial symmetry were…”

“…In the axial case the extension of (17) to three bands called COR 3B introduces [20][21][22] two additional parameters e,3 and ~5/21j + 13/2), so that we end up with fewer parameters in the triaxial case than in the axial case, contrary to a common feeling. In the axial case of three bands K,K+I and K+2 with K4=1/2 coupled by the Coriolis force one has [20][21][22] a six parameters problem (there is no decoupling parameter) as in the case of the assumption of an unique triaxial intrinsic state and three values of K (assumption TRI 3K). This provides also an interesting case for comparison which we shall use in Sect.…”

“…4. These facts constitute valuable reasons for looking for another method in which it might be possible to avoid most of these problems 9 The extension to triaxial nuclei of the method of inversion of the eigenvalue problem previously developped [20][21][22] for axial symmetry appears particularly suited.…”

“…The aim of the present paper is to clarify the theoretical approach to odd Ir isotopes by attempting a coherent description of the three families of observed levels using the assumption of strong coupling of the odd quasi-particle to a triaxial rigid core. To avoid the increase of the number of parameters involved by the sophisticated approaches we mentioned, we extend to triaxial nuclei the method of inversion of the eigenvalue problem previously developped [20][21][22] for axial deformation. In Sect.…”

Extension of the multiphonon method to odd mass deformed nuclei

“…The rotation may contribute to the observed level energies in three different ways: The part 2h~[i(i+ 1) -K 21 is easy to evaluate; moreover, the recoil term h 2 cannot be estimated and, as usual, is expected to be negligible; finally, the effects of the Coriolis coupling can be calculated in the frame of the unified model of Bohr and Mottelson [4,5,23]. Therefore they cannot, a priori, be compared directly to the observed energies which contain contributions due to the rotational motion.…”