Structure of the (EC) decay strength function of Tb ( h)

Abstract

The strength function S β (E) for the β + (EC)-decay of 147g Tb (T 1/2 1.6 h) is measured by the method of total γ -rays absorption. The same strength function is deduced from the analysis of the 147g Tb decay scheme and 147 Gd level scheme. The thus derived strength functions are in quite good agreement with each other. Also, theoretical calculation of S β (E) by the microscopic quasiparticle-phonon model is carried out. The most characteristic properties of both the experimental and theoretical strength functions are pronounced resonances in S β (E).

Fine Structure of β-Decay Strength Function

“…No similar splitting of the peak (Figure 2) in S β (E) is observed in the GT β + /EC-decay of the spherical 147g Tb nucleus [3]. Slight splitting of the peak in S β (E) for 147g Tb gives comparable intensities of the components and is related to the so-called configurational splitting [12].…”

Fine structure of the 147gTb (1.6 h), 149Tb (4.15 h) and 151Tb (17.6 h) β+/EC decay strength functionsdecay strength functions

“…Slight adjustments of the proton singie-particle energies were done during the BCS calculation described below. It is worth noting that in the work [5] we used just pure Woods-Saxon energies for the single-particle terms of the hamiltonian and thus the present calculation is more realistic yielding a much better agreement of the calculated energies with the measured low-energy spectrum of 147Gd. In the MQPM the approximate ground state of the even-even reference nucleus is obtained from a BCS calculation.…”

“…Usually S#(E) is measured in MeV-ls -1 units, the B(GT) is measured in g2A/41r units and ft is in seconds. In this case [1,5]:…”

“…Usually S#(E) is measured in MeV-ls -1 units, the B(GT) is measured in g2A/41r units and ft is in seconds. In this case [1,5]: in particular the analysis of the MT = +1 Gamow-Teller resonance and its fine structure identification for 1478Tb (1.6 h) ~+/EC decay.…”

“…Agreement with the experimental excitation energies is good. The mixing of one-and three-quasiparticle components in the wave functions of the Tb and Gd nuclei was achieved by diagonaiization of the Hsl + His part of the quasiparticle h~rniltonian (5) in the basis containing the relevant one-quasiparticle and quasiparticle-phonon components. Spurious states were removed by inspection of the norm matrix.…”