Influence of pairing correlations on E1 transition probabilities in odd-mass deformed, rare-earth nuclei

Abstract

Theoretical calculations of E1 and E3 transition rates for deformed rare-earth nuclei are made, taking into account the retarding effect of pairing correlations. It is found that pairing correlation correction factors R improve the general agreement with experiment for one class ,of transition, viz. E1 with LlK = ± 1. However, the factors R generally cause poorer agreement for E1 with LlK = 0 and for E3 than results from simple use of Nilsson single-particle wave functions with no pairing corrections. The importance of taking into account wave function ~omponents admixed by the Corio lis coupling is illustrated by a calculation fitting the many E1' transition rates between two bands in Hf1" . 'It is further suggested that effects due to-ihreequasi-particle components (or, in other language, octopole phonon or' "effective charge" effects) are probably of great importance and deserve further study.

On the role of the coriolis and quasiparticle-phonon interactions in describingE1 transition probabilities in odd Eu and Tb isotopes

“…The [2,3,5,9]. The inclusion of the quasiparticle-phonon interaction apart from the Coriolis one improves essentially, as it will be shown below, the agreement with experimental data.…”

“…The Hamiltonian of intrinisc excitations Hintr = Hsw + Hpair + Hmm (2) contains an average field Hsw as a single-particle Saxon-Woods potential, monopole pairing interaction Hpair and the isoscalar and isovector multipole-multipole interaction Hmm with 2/z= 10, 1l, 20, 22, 30, 31 and 32.…”

“…It has long been known that octupole vibrational components together with the Coriolis mixing play an important role in enhanced E 1 transitions in odd deformed nuclei [1][2][3][4][5]. However, the microscopic calculations of E1 transitions, when both the Coriolis forces and quasiparticle-phonon interaction are taken into account were performed mainly in sixties [3,4] and since then were not improved.…”

Production et étude des isomères 179mHf et 177mYb

“…Probabilit6s des transitions El. -Dans le cadre d'une 6tude g6n6rale des probabilites des transitions E1 dans les noyaux def ormes des terres rares [13], [14], il est int6ressant de comparer les probabilités expérimentales des transitions E1 de 104 keV de 177MYb et de 215 keV de 179mHf aux previsions th6oriques du mod6le de Nilsson.…”

“…Le d6saccord entre ces probabilités et les probabilités th6oriques calcul6es [14] a partir du mod6le de Nilsson peut Atre caracterise indifferemment, soit par un facteur d'interdiction, FN = PilssonIP(,xp soit par un facteur de reduction, RN = 1l FN. On a Pour le rayonnement E1 de 321 keV de 177Hf qui correspond, comme les rayonnements de 104 keV de 117-Yb et de 215 keV de 179mHf, 4 une transition d'un neutron entre les niveaux 9/2 .p (624) et 7/2 -(514) de Nilsson, on a [14] 11 est possible, dans le cas precis des deux niveaux de Nilss ,n consid6r6s ici, d'expliquer quantitativement la reduction des probabilités expérimentales par rapport aux probabilités theoriques, en tenant compte de la force d'appariement des nucl6ons, negligee dans le mod6le de Nilsson. Cette force produit une reduction de la probabilite de transition qui peut etre caract6ris6e par un facteur de r6duction R. La courbe de la figure 4 repr6sente la variation, en fonction du nombre N de neutrons, de ce facteur R, calcul6 [14] en utilisant une force constante.…”