Ackermann, D.

Andel, B.

Andreyev, A. N.

Antalic, S.

Bianco, L.

Heßberger, F.

Hofmann, S.

Huyse, M.

Kalaninova, Z.

Kindler, B.

Lommel, B.

Mann, R.

Page, R. D.

Sapple, P.

Thomson, J.

Van Duppen, P.

Venhart, M.

GSI Repository

Decay of 201−203Ra∗Z. Kalaninova´†1, S. Antalic1, A.N. Andreyev2,3, F.P. Heßberger4,5, D. Ackermann4, B. Andel1,L. Bianco6, S. Hofmann4, M. Huyse7, B. Kindler4, B. Lommel4, R. Mann4, R.D. Page6, P. Sapple6,J. Thomson6, P. Van Duppen7, and M. Venhart8,11Comenius University, Bratislava, Slovakia; 2University of York, York, UK; 3ASRC, JAEA, Ibaraki, Japan; 4GSI,Darmstadt, Germany; 5Helmholtz Institut Mainz, Mainz, Germany; 6University of Liverpool, Liverpool, UK; 7KULeuven, Leuven, Belgium; 8Institute of Physics, SAS, Bratislava, SlovakiaFor the most neutron-deficient radium isotopes not muchexperimental information about decay properties is avail-able up to now and in some cases reported data are not con-sistent. This was the motivation for our study of 201−203Ra.The investigated isotopes were produced in fusion-evaporation reactions 56Fe + 147,149Sm at the velocity fil-ter SHIP at GSI in Darmstadt. After separation from otherparticles, evaporation residues (ERs) were implanted intoa 16-strip position sensitive silicon detector (PSSD) regis-tering their α decays. α particles escaping from the PSSDwere recorded by a system of six silicon detectors placedin the backward hemisphere covering 80 % of 2 π. Nucleiwere identified based on time and position correlations ofER implantations and their subsequent α decays.Only two decay chains of 202Ra were reported until now,each one in different measurement [1,2]. Both experimentswere performed at the RITU separator at JYFL yieldingdifferent values for α-decay energies (7860(60)keV [1]and 7740(20) keV [2]) and half-lives (0.7+3.3−0.3 ms [1] and16+30−7 ms [2]). In our study we registered 16 correlationchains attributed to the decay of 202Ra. Nuclei were pro-duced in the reaction 56Fe + 149Sm at several beam ener-gies in the range of (244-275)MeV. Measured α-decay en-ergy and half-life were 7722(7) keV and 3.8+1.3−0.8 ms. Thereduced α-decay width (δ2α) for this decay was 210+70−50 keVcalculated using the Rasmussen formula [3] and assumingΔL = 0. It confirms the trend of increasing δ2α at decreas-ing neutron number for radium isotopes. This is consistentwith the trends for neighboring even-even radon and tho-rium isotopic chains [4].Prior to our study, only one decay chain attributed to201Ra was reported at RITU [2]. Based on daughter andgranddaughter decay properties it was assumed to origi-nate from the 13/2+ state. In our measurement we reg-istered one ER-α1-α2-α3 correlation chain in the reaction56Fe + 147Sm at Ebeam = 249 MeV with parent α-decay en-ergy of 7842(12) keV and a half-life of 8+40−4 ms. Propertiesof the α2 and α3 decays correspond to known decays ofthe 3/2− states in 197Rn and 193Po, respectively. Based onthe deduced unhindered character of the observed α1 decaywe assume that it originates from the 3/2− state in 201Ra.We localized the 13/2+ state in this isotope at 260(30) keV,which follows the trend of decreasing energies of the 13/2+∗Work supported by Slovak Research and Development Agency andSlovak grant agency VEGA.† Zdenka.Kalaninova@fmph.uniba.skNneutron number 105 110 115 120 125level energy (keV)02004006008001000120086) = ZRn (88) = ZRa (+ 13/2- 3/2 - 5/2+ 13/2- 3/2- 5/2Figure 1: (Color online) Energy level systematics for odd-A radon (dashed lines and open symbols) and radium (solidlines and full symbols) isotopes.levels at decreasing N for radium isotopes (see Fig. 1). Asimilar trend is also seen in radon isotopes.The 203Ra isotope was observed in two studies reportingseven [1] and ∼ 30 decay chains [2] with significantly dif-ferent decay properties for the 3/2− state. We detected nineER-α1-α2 correlation chains in the reaction 56Fe + 149Smat beam energies from 244 to 275 MeV, which were as-signed to 203Ra. Five of them were attributed to the decayof the 3/2− state and four to the 13/2+ state based on thereference values for parent and daughter decays. However,neither for 203Ra, nor for its α-decay daughters, the orderand energy difference between the 3/2− and 13/2+ states isknown. Our values of Eα = 7575(10)keV, T1/2 = 50+40−15 msfor the 3/2− state and Eα =7607(8)keV, T1/2 = 37+37−12 msfor the 13/2+ state agree with values in Ref. [2]. However,the ratio of decays from the 13/2+ and 3/2− states from ourdata is 0.8(5), which is in contrast to the previous measure-ments [1,2], where more decays were observed from the13/2+ state (with corresponding ratio∼ 6 [1] and∼ 3 [2]).References[1] M. Leino, et al., Z. Phys. A 355, 157 (1996).[2] J. Uusitalo, et al., Phys. Rev. C 71, 024306 (2005).[3] J.O. Rasmussen, Phys. Rev. 113, 1593 (1959).[4] Z. Kalaninova´, et al., submitted to Phys. Rev. C.NUSTAR-SHE-04 GSI SCIENTIFIC REPORT 2013128 doi:10.15120/GR-2014-1-NUSTAR-SHE-04

Decay of $^{201-203}Ra$

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Decay of $^{201-203}Ra$

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Decay of 201−203Ra^{201-203}Ra201−203Ra

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Decay of $^{201-203}Ra$