Continuous evolution from quasi particle excitation mode to collective excitation: study of +ve parity band in ¹⁰⁶Ag nucleus

The theory of shears mechanism came as a surprise to solve the puzzle of high-spin M1 bands in near spherical Pb isotopes with falling B(M1) rates. The commonly observed shears bands, also known as the magnetic rotation bands are generated when the quasi-particle angular momenta of particle- type and hole-type align themselves perpendicularly at the band-head, forming blades of a shear. The repulsive nature of the particle- hole interaction give rise to a band by closing these shear blades simultaneously. Apart from a near spherical nucleus the shears structure can evolve in a sufficiently deformed nucleus, in which case it competes with the core rotation to generate the high-spin states