Speaker
Description
Thermal motion and thermodynamic properties of nuclei influence nucleosynthesis in stellar environments. In macroscopic conductors, pairing phase transitions show a sharp heat capacity discontinuity at the transition temperature [1]. However, in nuclei, the smaller radius compared to pair coherence length leads to fluctuations, suppressing the discontinuity and resulting in a shallow "kink" (S-shape) in heat capacity at the transition temperature [2]. Till now, pairing phase transitions are observed mostly in even-even nuclei [3,5] due to nucleonic Cooper pair breaking. Recently, S-shaped heat capacity was seen in odd-odd deformed 184Re, suggesting deformation-induced pairing[4]. Similar discontinuities appear in even-odd 183,185W[5]. These findings prompt further study of odd-odd and even-odd systems, especially nuclei crucial for s-process and r-process nucleosynthesis, to explore pairing correlations and nuclear structure in diverse mass regions. We investigated pairing phase transition in hot rotating 69Zn (odd-even) using nuclear level density (NLD) data experimentally extracted from γ-gated particle spectra.
Experimental NLDs are compared with microscopic exact pairing plus independent-particle mode (EP+IPM), Hartree-Fock BCS (HFBCS), and Hartree-Fock-Bogoliubov combinational (HFBC) calculations at finite temperature. EP+IPM with recommended quadrupole deformation parameter β2 accurately reproduces experimental NLDs, outperforming HFBCS and HFBC methods [6]. The heat capacity calculated using the EP+IPM NLD clearly exhibits a sharp S-shape(Fig. 1(a)), unexpected for even-odd systems, insensitive to β2 adjustments, indicating robustness. However, (Fig. 1(b)) shows increasing/decreasing pairing gaps enhances/destroys the S-shape, implying pairing correlations play a crucial role. Deformation-induced pairing correlation explains the S-shaped heat capacity in 69Zn, suggesting pairing correlations persist in hot rotating odd-even nuclei, providing insights into nuclear structure and pairing mechanisms [6].
Reference
/1/ B. Muhlschlegel, D. J. Scalapino, and R. Denton, Physical Review B 6, 1767(1972)
/2/ S. Liu and Y. Alhassid, Phys. Rev. Lett 87, 022501 (2001).
/3/ R. Chankova et al., Phys. Rev. C 73, 034311 (2006).
/4/ Balaram Dey et al., Phys. Lett. B 789, 634 (2019).
/5/ K. Kaneko and M. Hasegawa, Phys. Rev. C 72, 024307 (2005).
/6/ Enakshi Senapati et al., J. Phys. G: Nucl. Part. Phys. 50 (2023) 075104.