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arXiv · 2203.15659

Study of the production and decay properties of neutron-deficient nobelium isotopes

M. S. Tezekbayeva·A. V. Yeremin·A. I. Svirikhin·A. Lopez-Martens·M. L. Chelnokov·V. I. Chepigin·A. V. Isaev·I. N. Izosimov·A. V. Karpov·A. A. Kuznetsova·O. N. Malyshev·R. S. Mukhin·A. G. Popeko·Yu. A. Popov·V. A. Rachkov·B. S. Sailaubekov·E. A. Sokol·K. Hauschild·H. Jacob·R. Chakma·O. Dorvaux·M. Forge·B. Gall·K. Kessaci·B. Andel·S. Antalic·A. Bronis·P. Mosat
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Abstract

The new neutron-deficient isotope $^{249}$No was synthesized for the first time in the fusion-evaporation reaction $^{204}$Pb($^{48}$Ca,3n)$^{249}$No. After separation, using the kinematic separator SHELS, the new isotope was identified with the GABRIELA detection system through genetic correlations with the known daughter and granddaughter nuclei $^{245}$Fm and $^{241}$Cf. The alpha-decay activity of $^{249}$No has an energy of 9129(22)$~$keV and half-life 38.3(2.8) ms. An upper limit of 0.2\% was measured for the fission branch of $^{249}$No. Based on the present data and recent information on the decay properties of $^{253}$Rf and aided by Geant4 simulations, the ground state of $^{249}$No is assigned the 5/2$^+$[622] neutron configuration and a partial decay scheme from $^{253}$Rf to $^{245}$Fm could be established. The production cross-section was found to be $\sigma$(3n)=0.47(4) nb at a mid-target beam energy of 225.4 MeV, which corresponds to the maximum of the calculated excitation function. Correlations of the $^{249}$No alpha activity with subsequent alpha decays of energy 7728(20) keV and half-life $1.2_{-0.4}^{+1.0}$ min provided a firm measurement of the electron-capture or $\beta^{+}$ branch of $^{245}$Fm to $^{245}$Es. The excitation function for the 1n, 2n and 3n evaporation channels was measured. In the case of the 2n-evaporation channel $^{250}$No, a strong variation of the ground state and isomeric state populations as a function of bombarding energy could be evidenced.

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M. S. Tezekbayeva, A. V. Yeremin, A. I. Svirikhin, A. Lopez-Martens, M. L. Chelnokov, V. I. Chepigin, A. V. Isaev, I. N. Izosimov, A. V. Karpov, A. A. Kuznetsova, O. N. Malyshev, R. S. Mukhin, A. G. Popeko, Yu. A. Popov, V. A. Rachkov, B. S. Sailaubekov, E. A. Sokol, K. Hauschild, H. Jacob, R. Chakma, O. Dorvaux, M. Forge, B. Gall, K. Kessaci, B. Andel, S. Antalic, A. Bronis, P. Mosat. 2022-03-29. Study of the production and decay properties of neutron-deficient nobelium isotopes. https://doi.org/10.1140/epja%2Fs10050-022-00707-9

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