Excitation of giant spin-isospin multipole vibrations in 54, 56Fe and 58, 60Ni

Abstract

The s e l e c t i v i t y and t h e s u r p r i s i n g s i m p l i c i t y of response function f o r spin-isospin t r a n s i t i o n s with t h e (p,n) r e a c t i o n a t intermediate energies has been AL=O t r a n s f e r s f o r 5 4 9 5 6~e t a r g e t s . I n t h e case of used t o study the spin-isospin c o r r e l a t i o n s i n n u c l e i t h e N i i s o t o p e s , a comparison may be made with t h e M1 (see Ref. 1 and o t h e r references within). The zero s p e c t r a obtained from e l e c t r o -e x c i t a t i o n . 3 9 degree s p e c t r a have been used t o o b t a i n t h e AL = 0 The experimental r e s u l t s and a n a l y s i s f o r the response function of n u c l e i while t h e measured2 energy 5 8~i ( p , n ) 5 8~u r e a c t i o n have been published3; t h e dependence of the e f f e c t i v e n u c l e o n n u c l e u s i n t e r a c t i o n a n a l y s i s f o r t h e o t h e r i s o t o p e s is i n progress.r e s u l t i n g from the spin-isospin terms i n the The double d i f f e r e n t i a l c r o s s s e c t i o n of L = 0 nucleonnucleon f o r c e has been employed t o i d e n t i f y t h e s t r e n g t h observed a t ( 3~ = 0' f o r t h e 5 8~i ( p , n ) 5 8~u spin-isospin o r Gamow-Teller strength. Other r e a c t i o n is presented i n Fig. l b and i s compared i n multipoles observed a t higher e x c i t a t i o n energies Fig. l c with the B(M1)C s t r e n g t h reported4 f o r t h e i n d i c a t e a maximum d i f f e r e n t i a l c r o s s s e c t i o n a t 5 8~i ( e , e ' ) reaction. The l o c a t i o n s of known 1+ e x c i t e ds l i g h t l y higher angles and have been i n t e r p r e t e d a s s t a t e s i n A = 58 n u c l e i a r e shown i n Fig. la. (AL = 1, AS = 1) and (AL = 2, AS = 1) e x c i t a t i 0 n s . l *permanent address: C e n t r a l Research I n s t i t u t e f o r W e have obtained 160 MeV (p,n) d a t a on 5 4 * 5 6~e and Physics, Budapest, Hungary.5 8 * 6 0~i and 120 MeV d a t a f o r t h e 5 8~i ( p , n ) 5 8~u r e a c t i o n 1) C. Gaarde e t a l . , Nucl. Phys. A369, 258 (1981).i n order t o study t h e response function of 5 8 * 6 0~i 2) T.N. Taddeucci e t a l . , Phys. Rev. C 25, 1094 (1981).t a r g e t s t o spin-isospin t r a n s i t i o n s characterized with 3) J. Rapaport e t al., Phys. Lett. 119B, 61 (1982). AL = 0, AL = 1 and AL = 2 t r a n s f e r s and t o study t h e 4) R.A. Lindgren e t a l . , Phys. Rev. C 3, 1789 (1976).

Tensor interaction in mean-field and density functional theory approaches to nuclear structure

“…The experimentally observed strength from 10 to 20 MeV excitation energy (with respect to the ground state of the target nuclei) is about 50% of the model-independent non-energy weighted sum rule (NEWSR); this percentage becomes about 70% if the whole strength in the neighbouring energy region is collected [120]. It is expected that the tensor force has an effect on the centroid of the GT resonance (GTR), in analogy with what discussed for the case of the M1 resonance in Sec.…”

Low-energy magnetic dipole response in 56Fe from high-resolution electron scattering

“…The GT + and GT − strengths in 56 Fe have been studied with the (p, n) [18] and (n, p) [19] charge-exchange reactions, respectively. A study of the M1 response in 56 Fe serves as an interesting test of the theoretical approaches.…”

Shell-model calculations of stellar weak interaction rates. I. Gamow-Teller distributions and spectra of nuclei in the mass range A = 45–65

“…2; they exhibit the same peak structure as the GT data, but the conversion factor is slightly energy dependent. The two data sets [27,28] appear to have a small energy offset (≈ 0.5 MeV), which might be interpreted as the experimental energy uncertainty.…”

“…Informations about the GT − strength distribution has been determined experimentally from (p,n) chargeexchange reaction measurements for the nuclei 54,56 Fe and 58,60 Ni [27,28]. As these Gamow-Teller transitions change a neutron into a proton, they can lead, for a nucleus with neutron excess and ground state isospin T , to 3 different isospins (T, T ± 1) in the daughter nucleus.…”

“…[28] reports the forward-angle (p,n) cross sections for 54 Fe, without conversion into GT strength functions. These data are shown in the upper parts of Fig.…”