Level structure of the Ge, Se, and Kr $(N=52, 53)$ isotopes within the framework of the interacting boson model

The levels structure and electromagnetic transitions of ${}^{84,85}\mathrm{Ge},{}^{86,87}\mathrm{Se}$, and ${}^{88,89}\mathrm{Kr}$ isotopes have been investigated in the interacting boson model (IBM-2), including the interacting boson-fermion model (IBFM-2), as a first application of the model. In the calculation, the fermions are allowed to excite to the $2d_{5/2},1g_{7/2},2d_{3/2},3s_{1/2}$, and $1h_{11/2}$ single-particle orbitals. The results of the model calculation have been found to be in good agreement with both shell-model and available experimental data. Also the strong staggering of the yrast band has been found to be well described.

Figure 1

Variation in level energy of ${}_{32}^{84}{\mathrm{Ge}}_{52},{}_{34}^{86}{\mathrm{Se}}_{52}$, and ${}_{36}^{88}{\mathrm{Kr}}_{52}$ isotopes as a function of ${\kappa }_{\pi \nu }$ and ${\varepsilon }_d$ parameters; all the other parameters were kept at their best-fit values. The symbol represents the experimental data [17, 18, 30].

Figure 2

Comparison between excitation energy levels of the IBM calculation and experimental data [17, 18, 30] for the ${}_{32}^{84}{\mathrm{Ge}}_{52},{}_{34}^{86}{\mathrm{Se}}_{52}$, and ${}_{36}^{88}{\mathrm{Kr}}_{52}$ isotopes.

Figure 3

Same as Fig. 2, but for the ${}_{32}^{85}{\mathrm{Ge}}_{53},{}_{34}^{87}{\mathrm{Se}}_{53}$, and ${}_{36}^{89}{\mathrm{Kr}}_{53}$ isotopes.The numbers indicate twice the angular momentum.

Figure 4

Staggering of the calculated excitation energy levels for ${}_{32}^{85}{\mathrm{Ge}}_{53},{}_{34}^{87}{\mathrm{Se}}_{53}$, and ${}_{36}^{89}{\mathrm{Kr}}_{53}$ isotopes. The shaded symbol represents experimental data [18].