Systematics of 2^+_1 States in N = 82 Even-even Isotones

In this paper, we study the systematics of the 2^+_1 states in the N=82 even-even isotones with proton numbers between 52 and 72. We calculate the level energies of the 0^+_1, 2^+_1 states and the electric quadrupole reduced transition probabilities B(E2; 2^+_1 \rightarrow 0^+_1), in the framework of the nuclear shell model with a monopole- and multipole-optimized realistic interaction. Our calculations yield good agreement with the experimental data and show a 2.5 MeV gap at Z=64 subshell closure in ¹⁴⁶Gd. We predict that the B(E2; 2^+_1 \rightarrow 0^+_1) value for ¹⁴⁶Gd is close to those for ¹⁴²Nd and ¹⁴⁴Sm, and the values increase rapidly from ¹⁴⁸Dy to ¹⁵²Yb.