Influence of the hexadecapole deformation on the two neutrino double-beta decay

The two neutrino double beta � � � 2� decay of 94,96 Zr, 98,100 Mo, 104 Ru, 110 Pd, 128,130Te and 150Nd nuclei for the 0+! 0+ transition is studied in the PHFB model in conjunction with the pairing plus quadrupole-quadrupole plus hexadecapole-hexadecapole effective two-body interaction and the effect of the latter is investigated on the calculation of nuclear transition matrix elements M2�. The reliability of the intrinsic wave functions of parent and daughter nuclei involved in the � � � 2� decay of above mentioned nuclei is established by obtaining an overall agreement between a number of theoretically calculated spectroscopic properties, namely the yrast spectra, reduced B(E2:0+ ! 2+) transition probabilities, static quadrupole moments Q(2 + ) and g-factors g(2 + ) and the available experimental data. The effect of deformation on M2� is also investigated to inveterate its inverse relation with nuclear deformation.