Experimental study of nuclei in the vicinity of the “island of inversion” through the fusion-evaporation reaction

Abstract

We report the first observation of high-spin states in nuclei in the vicinity of the "island of inversion", populated via the 18 O+ 18 O fusion reaction at an incident beam energy of 34 MeV.The fusion reaction mechanism circumvents the limitations of non-equilibrated reactions used to populate these nuclei. Detailed spin-parity measurements in these difficult to populate nuclei have been possible from the observed coincidence anisotropy and the linear polarization measurements.The spectroscopy of 33,34 P and 33 S is presented in detail along with the results of calculations within the shell model framework.

Level lifetimes inP32obtained using the Doppler-shift attenuation method with thick molecular targets

“…The calculated density of Ta 2 O 5 from simple averaging of the elemental solid densities is 5.76 g/cm 3 while the maximum theoretical density is 8.2 g/cm 3 . The latter is also recorded in the compound database of the SRIM package.…”

“…The details of the experimental setup are outlined in Ref. [3]. The neutron-rich 18 γ-rays have been detected using the Indian National Gamma Array (INGA) [13], stationed at the 15 UD Pelletron Accelerator Centre at IUAC, New Delhi.…”

“…It is noteworthy to mention that the 18 O target can only be fabricated in a molecular form such as Vanadium (V 2 O 5 ) or Tantalum (Ta 2 O 5 ) Pentoxide. Our group has reported the use of thick Ta 2 O 5 target, enriched in 18 O, in the spectroscopic studies of these nuclei [3,5,6]. The Doppler lineshapes observed for the γ-ray transitions in these experiments cannot be analyzed within the purview of the standard LINESHAPE package.…”

“…We have previously reported our spectroscopic investigation of the 26 Mg, 32,33,34 P, 33 S [3,5,6], using heavy-ion induced fusion-evaporation reactions, wherein the level structures have been extended to higher spin domain. However, an unambiguous understanding of the structure requires information on the excited level lifetimes that helps us to identify the underlying microscopic configurations of the states.…”

“…26 Mg, 33 S, 32,33,34 P, have been the subjects of extensive experimental and theoretical investigations [1][2][3][4][5][6] in recent times. The low lying positive parity states in these nuclei are expected to be dominated by pure sd configurations while the negative parity states involve excitations to the f p shell.…”