Well-developed deformation in 42Si

TL;DR

This study used gamma-ray spectroscopy with radioactive beams to investigate excited states in silicon isotopes, revealing rapid development of nuclear deformation from N=24 to N=28, especially in 42Si.

Contribution

First detailed gamma-ray spectroscopy measurement of 42Si confirming its well-developed deformation at N=28.

Findings

Observation of a 742 keV gamma line confirming 2+ state in 42Si.

Identification of the 4+_1 state at 2173 keV in 42Si.

Energy ratios indicating rapid deformation development in Si isotopes.

Abstract

Excited states in 38,40,42Si nuclei have been studied via in-beam gamma-ray spectroscopy with multi-nucleon removal reactions. Intense radioactive beams of 40S and 44S provided at the new facility of the RIKEN Radioactive Isotope Beam Factory enabled gamma-gamma coincidence measurements. A prominent gamma line observed with an energy of 742(8) keV in 42Si confirms the 2+ state reported in an earlier study. Among the gamma lines observed in coincidence with the 2+ -> 0+ transition, the most probable candidate for the transition from the yrast 4+ state was identified, leading to a 4+_1 energy of 2173(14) keV. The energy ratio of 2.93(5) between the 2+_1 and 4+_1 states indicates well-developed deformation in 42Si at N=28 and Z=14. Also for 38,40Si energy ratios with values of 2.09(5) and 2.56(5) were obtained. Together with the ratio for 42Si, the results show a rapid deformation development of Si isotopes from N=24 to N=28.