Systematics of low-lying dipole strengths in odd and even Dy and Gd isotopes

Abstract

Photon scattering experiments on the odd, deformed nuclei ' " Dy and ' Gd provided detailed information on the excitation energies and transition probabilities of low-lying dipole excitations. In the case of the even-even nuclei ' ' Dy in addition spins and parities of the excited states could be determined model independently by measuring the angular distributions and the linear polarization of the scattered photons using a Compton polarimeter. The results are compared with the systematics obtained for the neighboring even-even isotopes ' Dy and ' ' ' Gd in previous photon scattering experiments. Whereas in the odd Dy isotopes a concentration of dipole strength is observed, which fits nicely into the systematics of the orbital M1 mode, the dipole strength in ' Gd is completely fragmented into about 90 transitions.

Photon strength functions in Gd isotopes studied from radiative capture of resonance neutrons

“…Finally, data on the reduced M1 strength B(M1) ↑ of the ground-state transitions are available from (γ, γ ) measurements for all stable eveneven rare-earth nuclei [27] and several odd rare-earth nuclei [30,31,33,34,49]. In the case of a couple of even-even nuclei, data from (e, e ) experiments confirm the results from (γ, γ ) experiments [26,51].…”

“…The limited experimental sensitivity prevents observation of all these transitions in the NRF experiments. This fact led to smaller observed SM strength in odd nuclei compared to even-even neighbors [30][31][32][33]. Attempts to estimate the missing strength in NRF reaction in odd nuclei were made using a fluctuation analysis [33,34].…”

Dipole strength distribution and specific properties of excitations in the second minimum in actinide nuclei

“…In measurements, several doubly even deformed nuclei in the rare-earth and actinide regions have been studied [3,4,5,6,7]. The electric-dipole excitation modes of deformed nuclei have been simultaneously observed in these and other measurements [4,5,7].…”

Magnetic Dipole Sum Rules for Odd-Mass Nuclei

“…A survey [7] of scissors states in deformed odd-mass nuclei within the framework of the interacting boson-fermion model (IBFM) [8] predicted strong fragmentation and sizable symmetric (single-particle dominated) and nonsymmetric (scissors) M1 strength. Initial measurements on odd nuclei (Dy, Gd, Tb) indicated missing B͑M1͒ " strength compared to the strength observed in the neighboring even-even nuclei [9][10][11]. On the other hand, in 167 Er these M1 strengths were found to be comparable, with appreciable contribution coming from higher energies not accessed in previous experiments [12].…”