Discovery of an <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:msup> <mml:mrow> <mml:mi>I</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>π</mml:mi> </mml:mrow> </mml:msup> <mml:mo>=</mml:mo> <mml:mn>1</mml:mn> <mml:msup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> Isomer in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mmultiscripts> <mml:mrow> <mml:mi>Yb</mml:mi> </mml:mrow> <mml:mprescripts/> <mml:none/> <mml:mrow> <mml:mn>150</mml:mn> </mml:mrow> </mml:mmultiscripts> </mml:mrow> </mml:math> : Nature of the Longest <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> Isomeric Chain

Delayed γ-ray spectroscopy was performed for evaporation residues produced in the ^{58}Ni+^{96}Ru reaction. A new isomer in _{ 70}^{150}Yb (Z=70, N=80) with a half-life of 0.62(5) μs was identified at an excitation energy of 2872(2) keV. Its spin-parity is assigned as (10^{+}) and a decay scheme is proposed based on a strong analogy with that of the isotonic _{ 68}^{148}Er. Previously, the 10^{+} isomers were observed in the N=80 even-Z isotones from the neutron-rich _{ 46}^{126}Pd to the neutron-deficient _{ 68}^{148}Er. For the first time, by combining experimental data and comprehensive large-scale shell-model calculations, we clearly identify the configurations of these isomers and demonstrate that they all exhibit seniority structures. These findings firmly establish a configuration change in the 10^{+} isomeric chain, from a pair of maximally aligned 1h_{11/2} neutrons (holes) to a pair of maximally aligned 1h_{11/2} protons around the Z=64 subshell closure. This transition serves as a unique isomeric relay underpinning the persistence of the isomeric chain.