Structural Investigation in A ≈ 90 Mass Region and Comparison in Its Vicinity

In the investigations of the level structure of A \approx 90 nuclei, whose numbers of protons and neutrons are close to the Z = 40 semimagic number and N = 50 magic number, have become a hot spot in nuclear physics. The aim of this work is to further probe the characteristics of single-particle excitation, core breaking, high-j intruder states and isomeric states in the A\approx 90 mass region based on the existing experimental results. Investigations show that the low energy levels of the odd-A nuclei originate from their neighboring even-even nuclei coupled to a valence nucleon. The systematics of the 2_1^+ excitation energies and the values of \rmE_4_1^+/\rmE_2_1^+ indicate that the N = 56 subshell closure may appear at Z = 40 (41) and disappear for Z > 42 nuclei. Furthermore, in this mass region, the strong \rmE2 transitions at low or medium spins are interpreted as the recoupling of the pure protons in (f_5/2^, p_3/2^, p_1/2^, g_9/2^) orbits, and the strong M1 transitions are explicated by moving proton from the (f_5/2^, p_3/2^, p_1/2^) orbits to the g_9/2^ orbit, coupling to a neutron excitation from the g_9/2^ orbit across N = 50 closed shell into the d_5/2^ orbit. The isomeric states in odd-A nuclei with N = 50 (51) can be interpreted as a spin-aligned configuration in which a single neutron or proton couples with a fully aligned proton pair in the \pi g_9/2^ orbit.