Experimental Evidence for Quartet Structure in Cr and Ti Isotopes

Abstract

The (~0 , C) 0. '-transfer reaction has been studied on several Ca and Ti target isotopes using the 40and 48-MeV~6 0 beams of the Saclay FN tandem Van de Graaff. This work is the natural extension of the previous one performed on various Fe and Ni target isotopes. As previously observed for Ni and Zn residual nuclei, a small number of levels are strongly and selectively excited at low energy. This n-transfer reaction appears, then, as a new spectroscopic tool to study four-nucleon correlations. In close connection with the previous data on Fe and Ni targets, the present article points out the importance in residual nuclei of the quartet structure: namely two protons and two neutrons mutually strongly bound and weakly coupled to the target core. A strong blocking effect on the quartet is observed as soon as a neutron-pair excess is present in the target ground state. This neutron blocking effect has been already observed in the Fe and Ni target case. The existence in the 1f-2p shell of quartetting phenomena, i.e. , the presence of four highly correlated nucleons giving rise to a quasirotational band, establishes the interplay between spherical and deformed states already known to exist in lighter nuclei.

The study of the (n, ?) and (n, ? ?) reactions on143Nd

“…The results of the least-squares fits (fit 2, 4 and 6 in Table 4) show that at the present stage of the statistics in the experimental (n, ~ e) spectrum the observed structure can be explained through Porter-Thomas fluctuations of both 7 and e Mdths. However, the surprising selectivity in population of states observed in direct a-transfer reactions [8][9][10]12] justifies the tentative assumption that the e decay of states which are involved in the (n, 7 a) process is of direct character, too. This assumption was used in the fits 3, 5 and 7 of Table 4.…”

“…However, a selective population has been observed [8], and also for the 14~ 12C)144Nd reaction [9] involving states in 144Nd at excitation energies of ,~ 8 MeV. The clustering of extra-core protons and neutrons into an e particle on the surface of the core has been considered successfully in the rotor model of quartets [-10] in order to interprete the spectra obtained from a-transfer reactions in light and medium nuclei [11,12].…”

Existence of higher nodal band states withα+Ca48cluster structure inTi52

“…52 Ti, which is a typical nucleus with two protons and two neutrons outside the doubly closed core 48 Ca analog to 20 Ne and 44 Ti, has been mostly studied in the shell model [22][23][24][25][26][27]. The ground band 0 + , 2 + and 4 + states are selectively enhanced in the α-transfer reactions such as 48 Ca( 16 O, 12 C) 52 Ti [28] and 48 Ca( 12 C, 8 Be) 52 Ti [29]. However a microscopic α+ 48 Ca cluster model calculation with Brink-Boeker force B1 using the generator coordinate method (GCM) [30] did not give the ground band as well as in the α+ 40 Ca cluster model calculation for 44 Ti.…”

Projectile structure effects in multi-nucleon and cluster transfers in16,18O+164Dy,208Pb reactions

“…The experimental data on the cross sections and energy distributions are compared with the results of theoretical calculations based on the independent single-neutron transfer process. The two nucleon transfer reactions provide useful information on the pairing correlations in nuclei [7,8]. The pairing correlation effects in the multi-nucleon transfer processes have been investigated in the 62 Ni + 206 Pb system at energies near the Coulomb barrier [9].…”