The first experimental evidence for the (M1+E2) mixed character of the 9.2 keV transition in Th-227

The 9.2 keV nuclear transition in Th-227 was studied in the beta(-)-decay of Ac-227 by means of the internal conversion electron spectroscopy to clarify the spin-parity assignment of the ground state and the two lowest excited states of Th-227. The transition multipolarity was proved to be of mixed character M1+ E2 and the spectroscopic admixture parameter delta(2)(E2/M1) = 0.695 +/- 0.248(vertical bar delta(E2/M1)vertical bar = 0.834 +/- 0.149) was determined. Nonzero value of delta(E2/M1) questioned the present theoretical interpretation of low-lying levels of Th-227. Calculations performed prefer the 1/2(+), 3/2(+), and 3/2(+) sequence instead of the adopted 1/2(+), 5/2(+) and 3/2(+) one for the 0.0, 9.2, and 24.3keV levels, respectively.Web of Science820art. no. 13659

Construction of beta spectrum on the basis of experimental nuclear decay data

International audienceA computer code for $\beta$-spectrum construction of 1300$+$ radionuclei has been created. The tools use the experimental nuclear data adopted and compiled in the ENSDF file and experimental or estimated parameters of shape factors. The final uncertainty on the calculated $\beta$-spectrum branch tries to deal with uncertainties on the radiation probability, the endpoint energy, and the shape factor parameters

Improved energy of the 21.5 keV M1 + E2 nuclear transition in

Using internal conversion electron spectroscopy, improved energy 21 541.5±0.5 eV was determined for the 21.5keV M1 + E2 nuclear transition in 151Eu populated in the electron capture decay of 151Gd . This value was found to agree well with the present adopted value but is much more accurate. A value of 0.0305±0.0011 derived for the E2 admixture parameter $\vert\delta(E2/M1)\vert$ from the measured conversion electron line intensities corresponds to the present adopted value. A possible effect of nuclear structure on the multipolarity of the 21.5 keV transition was also investigated

Experimental investigation of the 9.2 and 24.3 keV nuclear transitions in

The 9.2 and 24.3 keV nuclear transitions in $$^{\mathrm {227}}$$Th were studied in the \upbeta ^{-} decay of $$^{\mathrm {227}}$$Ac employing the internal conversion electron spectroscopy. Values of $$(9244.6 \pm 0.8)$$ and $$(24343.1 \pm 1.1)$$ eV were determined for their energies. The 24.3 keV transition was found to be of the mixed (M1 $$+$$ E2) multipolarity with the spectroscopic admixture parameter $$\delta ^{\mathrm {2}}$$$$(E2/M1)$$=$$(0.0116 \pm 0.0004)$$. Energies of $$(24342.9 \pm 1.2)$$, $$(28613.3 \pm 1.7)$$, and $$(37860.2 \pm 2.0)$$ eV were obtained respectively for the 24.3, 28.6, and 37.8 keV transitions in $$^{\mathrm {227}}$$Th by means of the gamma-ray spectroscopy. Natural atomic-level widths of $$(14.1 \pm 0.5)$$, $$(11.4 \pm 0.5)$$, $$(6.9 \pm 0.4)$$, $$(11.4 \pm 1.4)$$, $$(8.6\pm 1.2)$$, and $$(6.0 \pm 0.7)$$ eV for the M$$_{\mathrm {1}}$$-, M$$_{\mathrm {2}}$$-, M$$_{\mathrm {3}}$$-, N$$_{\mathrm {1}}$$-, N$$_{\mathrm {2}}$$-, and N$$_{\mathrm {3}}$$-subshells of thorium, respectively, were derived from conversion electron lines. The cross checking of the energy values of the 9.2, 15.1, and 24.3 keV nuclear transitions obtained by the ICES method is also given

An experimental investigation of the 15.1 keV M1 + E2 nuclear transition in

Using the internal conversion electron spectroscopy, the energy of the 15.1 keV $M1+E2$ nuclear transition in 227Th populated in the $\beta^{-}$ decay of 227Ac was determined to be $15098.6 \pm 1.0$ eV. This value is more accurate than the present accepted one by a factor of 200. The present uncertainty in the transition multipolarity was removed and it was found to be $M1+E2$ with the admixture $\vert\delta (E2/M1)\vert = 0.035 \pm 0.006$

First direct high-precision energy determination for the 8.4 and 20.7 keV nuclear transitions in

Energies of 8410.1 ± 0.4, 20743.9 ± 0.3, and 63121.6 ± 1.2 eV were determined for the 8.4 keV M1 + E2, 20.7 keV M1 + E2, and 63.1 keV E1 nuclear transitions in 169Tm (generated in the EC decay of 169Yb, respectively, by means of the internal conversion electron spectroscopy. The 169Yb sources used were prepared by vacuum evaporation deposition on polycrystalline carbon and platinum foils as well as by ion implantation at 30keV into a polycrystalline aluminum foil. The relevant conversion electron spectra were measured by a high-resolution combined electrostatic electron spectrometer at 7 eV instrumental resoluition. Values of 0.0326(14) and 0.0259(17) were derived from our experimental data for the E2 admixture parameter |δ (E2/M1)| for the 8.4 and 20.7 keV transitions, respectively. A possible effect of nuclear structure on multipolarity of the 20.7 keV transition was also investigated