Spectral features of vibrational Te isotopes

Abstract

The variation of collective vibrational spectra with varying $N$ displayed by the $Z=52$ Te isotopes, for less than $N=82$ closed shell, are of special interest. The spectral features of the ground band and the two and three phonon excited multiplets in $^{118--128}\mathrm{Te}$, are studied here empirically. The state energy $E({2}_{1}{}^{+})$ increases, and the energy ratio ${R}_{4/2}$ decreases with increasing neutron number $N$. Also the ${0}_{2}{}^{+}$ state rises up sharply, and the ${0}_{3}{}^{+}$ state follows it, unlike their relation in the E(5) symmetry. It is shown that $^{120}\mathrm{Te}$ isotope displays the weakly deformed status, and the heavier isotopes move towards the spherical harmonic vibrator status. The interacting boson model (IBM-1) is used to reproduce these spectral features of $^{118--124}\mathrm{Te}$, with use of slight variation of boson energy \ensuremath{\epsilon} and of the quadrupole interaction strength. In the microscopic approach, the dynamic pairing plus quadrupole model of Kumar and Baranger also reproduces these basic spectral features.