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Successful applications of the total absorption $\gamma$-spectroscopy $(TAGS)$ for the $\beta$-decay strength function $S_{\beta}(\textit{E})$ resonance structure study, methods of $TAGS$ spectra interpretation, and results of analysis of $S_{\beta}(\textit{E})$ structure for the Gamow-Teller $(GT)$ $ \beta^{+}/EC$ and $\beta^{-}$ -decays were summarized in [1,2]. Development of experimental technique allows application of methods of nuclear spectroscopy with high energy resolution for $S_{\beta}(\textit{E})$ fine structure measurement [2-4]. First results of the $S_{\beta}(\textit{E})$ fine structure study were summarized in [2,3].The combination of the $TAGS$ with high resolution nuclear spectroscopy may be applied for detailed decay schemes construction [2]. It was shown [2-4] that the high-resolution nuclear spectroscopy methods give conclusive evidence of the resonance structure of $S_{\beta}(\textit{E})$ for $GT$ and first-forbidden $(FF)$ $\beta$-transitions in spherical, deformed, and transition nuclei. High-resolution nuclear spectroscopy methods [2-5] made it possible to demonstrate experimentally the reveal splitting of the peak in the $S_{\beta}(\textit{E})$ for the $(GT)$ $ \beta^{+}/EC$-decay of the deformed nuclei into two components.
The operating principle of a total-absorption $\gamma$-spectrometer is based on summation of the energies of the cascade $\gamma$-rays produced after $\beta$-decay to excited levels of the daughter nucleus in $4{\pi}$-geometry. There are two methods of the $TAGS$ spectra analysis [1]. In the first one it is necessary to identify the total absorption peaks in $TAGS$ spectra and have $4{\pi}$-spectrometer with exponential energy dependence of the photoefficiency (i.e., the ratio of the number of pulses in the total absorption peak to the number of $\gamma$-ray incident on the detector) for $\gamma$-ray registration. Only in this case the efficiency of $TAGS$ peak registration does not depend on the details of decay scheme [1,3]. This method gives good results, but can be applied for nuclei with total $\beta$-decay energy $ \textit{Q}_{\beta}$ less than $5-6 MeV$. Quantitative characteristics may be obtain as a rule only for one ($\beta^{-}$-decay) peak and for two peaks ($\beta^{+}/EC$-decay) in $S_{\beta}(\textit{E})$ [1-3].
The second method is based on so called response function application, but a lot of assumption must be done for extraction the $S_{\beta}(\textit{E})$ shape from the $TAGS$ spectrum shape. Analysis depends on the assumptions [1] about the decay scheme which as a rule is not known. It is very difficult to estimate the associated systematic errors of such analysis [1] and only qualitative information about $S_{\beta}(\textit{E})$ may be obtained.
$TAGS$ can’t distinguish the $GT$ and $FF$ transitions and don’t take into account the conversion electron emission, which give the systematic uncertainties, especially for high $Z$.
In this report some results of $TAGS$ spectra analysis are considered. It is shown that only combination of $TAGS$ with high resolution nuclear spectroscopy methods may give the quantitative information about $S_{\beta}(\textit{E})$.
- Yu.V. Naumov, A.A. Bykov, I.N. Izosimov, Sov. J. Part. Nucl., $\textbf{14}$, 175(1983). https://www.researchgate.net/publication/233832321
- I.N. Izosimov, Phys. Part. Nucl., $\textbf{30}$, 131(1999). DOI: 10.1134/1.953101
- I.N. Izosimov, et al, Phys. Part. Nucl., $\textbf{42}$, 1804(2011). DOI: 10.1134/S1063779611060049
- I.N. Izosimov, et al, Journal of Physics: Conference Series, $\textbf{381}$, 012054 (2012). DOI:10.1088/1742-6596/381/1/012054
