<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Th</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>229</mml:mn><mml:mi>m</mml:mi></mml:mrow></mml:mmultiscripts></mml:math> isomer from a nuclear model perspective

The physical conditions for the emergence of extremely low-lying nuclear isomer $^{229m}$Th at approximately 8 eV are investigated in framework our recently proposed structure model. Our theoretical approach explains $^{229m}$Th-isomer phenomenon as result a very fine interplay between collective quadrupole-octupole and single-particle dynamics nucleus. We find that isomeric state can only appear rather limited model space deformations potential, with octupole deformation being crucial importance its formation. Within this model-described quantities exhibit smooth behaviour close to line isomer-ground quasi-degeneracy determined by crossing corresponding orbitals. comprehensive analysis confirms previous predictions reduced transition probabilities magnetic moment, while showing possibility variation ground-state moment value. These findings prove reliability suggest same dynamical mechanism could manifest other actinide nuclei giving general prescription search exploration similar phenomena.