Systematic investigation of the low-lying dipole excitations in even-even 124-136Ba isotopes

Magnetic and electric dipole excitations in the energy interval 2.0-4.0MeV are studied for the even-even 124-136Ba isotopes within the rotational, translational and Galilean invariant Quasiparticle Random Phase Approximation (QRPA). The calculations show that low-lying magnetic and electric dipole states have mainly \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$ \Delta K=1$\end{document} character. Systematical analysis of the summed excitation strengths of the scissors mode as a function of deformation parameters or the mass number A was also done. It is shown that in the even-even 124-136Ba isotopes, the dependence of the total B(M1) transition on \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$ \delta_{2}^{2}$\end{document} is nearly linear for the well-deformed isotopes. The agreement between the calculated excitation energies as well as the summed B(M1) values of the scissors mode and the available experimental data is quite good. In addition, we predicted E1 dipole excitations for the even-even 124-136Ba isotopes which have not been observed experimentally, yet.