Determination of 226Ra, 224Ra, 223Ra and 228Ra in mineral water samples of the Slovak Republic

The Slovak Republic is very rich in mineral water sources. In recent years, it has been discovered that a number of mineral waters in the Slovak Republic contain high levels of ²²⁶Ra and ²²⁸Ra. Moreover, there is a lack of information on ²²⁴Ra and ²²³Ra concentrations in mineral waters as well. The currently approved techniques for alpha emitting radium isotopes are based on radon emanation methods. Due to the long ingrowth periods required by these techniques, any ²²⁴Ra and ²²³Ra in the sample decay away and go undetected. For this reason, we have used an alpha spectrometric method for the simultaneous determination of ²²⁶Ra, ²²³Ra and ²²⁴Ra. Radium was concentrated by a lead sulphate co-precipitation. The precipitate was dissolved in EDTA and the radium isotopes were separated from possible interfering radionuclides using barium sulphate micro precipitation. The radium-barium precipitate was filtered and counted by alpha spectrometry. ¹³³Ba was used to quantify the yield by gamma spectrometry. In our laboratory, gamma spectrometry was also used for the determination of ²²⁸Ra in mineral water samples. Radium was concentrated by a lead-barium sulphate co-precipitation. ¹³³Ba was used to quantify the yield, found to be 97% on the average, by gamma spectrometry. Furthermore, the committed effective doses for ²²⁶Ra, ²²⁴Ra, ²²³Ra, ²²⁸Ra intake via ingestion of mineral waters for the members of public were calculated.     

229Ra的衰变纲图

用14MeV中子轰击Th靶,通过￣(232)Th(n,a)反应产生了￣(229)Ra,由放射化学分离技术从被照靶物质中分离出￣(229)Ra的活性,利用γ(X)谱学方法,首次观测到了属于￣(229)Ac的能量为14.5、15.6、18.8、21.8、22.5、44.0、47.5、55.0、63.0、69.6、93.6、94.1、98.5、102.2、104.5、106.1、161.1、171.5keV的18条新衰变γ射线,并建议了￣(229)Ra的部分衰变纲图.     

Laser trapping of 225Ra and 226Ra with repumping by room-temperature blackbody radiation

We have demonstrated Zeeman slowing and capture of neutral 225Ra and 226Ra atoms in a magneto-optical trap. The intercombination transition 1S0-->3P1 is the only quasicycling transition in radium and was used for laser-cooling and trapping. Repumping along the 3D1-->1P1 transition extended the lifetime of the trap from milliseconds to seconds. Room-temperature blackbody radiation was demonstrated to provide repumping from the metastable 3P0 level. We measured the isotope shift and hyperfine splittings on the 3D1-->1P1 transition with the laser-cooled atoms, and set a limit on the lifetime of the 3D1 level based on the measured blackbody repumping rate. Laser-cooled and trapped radium is an attractive system for studying fundamental symmetries.     

Exotic clustering in 222,224,226Ra

We describe the J^π = 0⁺, 2⁺, 4⁺, … ground state bands of ^222,224,226Ra, using a model in which these bands are treated as a ¹⁴C cluster orbiting the appropriate Pb core. For each isotope, we obtain good agreement with the measured half-life for the ¹⁴C decay of the 0⁺ ground state, as well as with the excitation energies and in-band E2 decays of other states of the ground state band. We also propose extensions of the model to deal with the observed low-lying J^π = 1⁻, 3⁻, 5⁻, … bands, their in-band E2 decays, and the E1 and E3 transitions connecting to the ground state bands.     

Investigation of224Ra in the226Ra(α, α′ 2n) reaction

Positive and negative parity bands have been followed up to 10⁺ (possibly 12⁺) and 11^? in²²⁴Ra and are compared to the corresponding bands in the isotone²²⁶Th. If a constant value of the intrinsic quadrupole moment is assumed for allE2 transitions in²²⁴Ra theE1/E2 branching ratios are consistent with an intrinsic dipole moment of ¦Q₁¦=0.032(3)e·fm. This small value, as compared to ¦Q₁¦=0.30(2)e·fm for²²⁶Th, can be explained by an almost complete cancellation of large positive liquid-drop and negative shell-model contributions.     

Nuclear fission of Ra and Th isotopes

The fission modes and the corresponding nuclear shapes of Ra and Th isotopes are considered. It is shown that the fission of ²¹⁶Ra is expected to be predominantly symmetric, in accordance with recent experimental findings.     

偶偶 Ra 同位素的八极形变研究

用反射不对称的相对论平均场理论(RAS-RMF)对偶偶Ra同位素的八极形变进行了系统研究,并与实验数据和有限力程小液滴模型(FRDM)结果进行了比较.结果表明：RAS-RMF理论很好地描述了Ra同位素的基态性质,计算的结合能、双中子分离能和形变与实验数据和FRDM一致.RAS-RMF理论获得的中子、质子密度分布清晰地展现出偶偶Ra同位素由球形逐渐转变为八极形变,到四极形变的过程,与实验观察的八极形变不稳定现象一致.     

The structure and spectroscopy of219Ra

The reassignment of spins in the low lying level structure of²¹⁹Ra obtained from the alpha decay of²²³Th and minor changes in the spins and the position of the first observed state in the spectroscopy from the nuclear reaction studies²⁰⁸Pb (¹⁴C, 3n)²¹⁹Ra make possible the correlation of these two level structures which were previously unconnected. The resulting level structure shows very tentativeK = 1/2^± and 5/2^± parity doublet bands and their evolution from anomalous rotational structures into vibrational like bands with alternating spins and opposite parities, reminiscent of weak coupling to an octupole correlated core. The comparison and contrast of the isobars²¹⁹Ra and²¹⁹Fr is also presented.One of us (RKS) wishes to thank the National Science Foundation for support under contract PHY92-07336 with Florida State University     

偶偶 Ra 同位素的八极形变研究

用反射不对称的相对论平均场理论(RAS-RMF)对偶偶Ra同位素的八极形变进行了系统研究,并与实验数据和有限力程小液滴模型(FRDM)结果进行了比较.结果表明：RAS-RMF理论很好地描述了Ra同位素的基态性质,计算的结合能、双中子分离能和形变与实验数据和FRDM一致.RAS-RMF理论获得的中子、质子密度分布清晰地展现出偶偶Ra同位素由球形逐渐转变为八极形变,到四极形变的过程,与实验观察的八极形变不稳定现象一致. 关键词： 反射不对称平均场(RAS-RMF) 八极形变 偶偶核     

Spectroscopy of excited states in216Ra

A gamma spectroscopic investigation of²¹⁶Ra was performed by means of the reactions²⁰⁶Pb(¹³C, 3n) and²⁰⁸Pb(¹²C, 4n). Yield functions, angular distributions,γ?γ coincidences, time centroid shifts and pulsed beam isomeric decay rates were measured. The yrast level structure is firmly established up to spin 14 and information on theγ-transitions from higher lying levels is also obtained. The configurations of the low-lying levels are discussed.     

Nuclear structure of 216 Ra at high spin

High-spin states of ²¹⁶Ra ( $\emph{Z}=88$ , $\emph{N}=128$ ) have been investigated through ²⁰⁹Bi(¹⁰B, 3n) reaction at an incident beam energy of 55?MeV and ²⁰⁹Bi(¹¹B, 4n) reaction at incident beam energies ranging from 65 to 78?MeV. Based on ??? coincidence data, the level scheme for ²¹⁶Ra has been considerably extended up to ~ 33 $\hbar$ spin and 7.2 MeV excitation energy in the present experiment with placement of 28 new ??-transitions over what has been reported earlier. Tentative spin-parity assignments are done for the newly proposed levels on the basis of the DCO ratios corresponding to strong gates. Empirical shell model calculations were carried out to provide an understanding of the underlying nuclear structure.     

The nuclear spectroscopy and structure of 223Ra

The level structure of ²²³Ra is reinterpreted in terms of $\text{3}\text{2}$^±, $\text{5}\text{2}$^±, and $\text{1}\text{2}$^± parity-doub The non-adiabatic rigid reflection-asymmetric rotor model reproduces the main features of the experimental data assuming the presence of octupole deformation β₃ ∼- 0.1. In particular, the experimental E1 transition rates are accounted for by the calculated permanent collective electricdipole moment.     

Level structure of217Rn and221Ra investigated in the alpha-decay225Th →221Ra →217Rn

The nuclei²²¹Ra and²¹⁷Rn have been investigated in the α-decay chain²²⁵Th→²²¹Ra →²¹⁷Rn through γ-ray and conversion-electron studies. The short-lived²²⁵Th nuclei (T _1/2=8min) were produced in the²²⁶Ra(α, 5n) reaction, and γ-rays and conversion electrons were measured — between the irradiation periods — in coincidence with αparticles. In²²¹Ra the five lowest levels are interpreted as members of aK=5/2 paritydoublet with ΔE_π=104 keV. These levels, as well as a higher-lying K^π=3/2⁺ band, are consistent with an octupole deformation of²²¹Ra, as expected from theoretical considerations. In²¹⁷Rn only three excited levels are observed, with a favoured α-decay to a 5/2⁺ excited level thus establishing positive parity for the ground state of²²¹Ra.     

Ra in geothermal and bottled mineral waters of Hungary

Geothermal waters have been used on a large scale for bathing, drinking and medical purposes, while the consumption of bottled mineral waters is increasing. In this work, radon and radium activity concentrations of thermal and bottled mineral waters, originating from different regions of Hungary, were studied by different radioanalytical methods. It was found that the thermal springs, which supply the world famous baths of Budapest along the right riverside of the Danube, have high ²²²Rn and ²²⁶Ra activity concentration: up to about 100 and 1 kBqm⁻³, respectively. The radium content of some investigated geothermal waters found in the NE region of the Great Hungarian Plain is even higher: up to several kBqm⁻³. The ²²⁶Ra content of bottled mineral waters, commercially available in Hungary, was determined by gamma-spectrometric method, applying radiochemical separation. The highest value exceeded 2 kBqm⁻³ in the case of the Apenta mineral water, which is a popular brand in Hungary, as well as in Europe and North America.     

Anisotropic alpha-emission in the223Ra decay chain

Anisotropic α-emission from nuclei in the decay chain from²²³Ra to²⁰⁷Tl has been observed using low temperature nuclear orientation in combination with high resolution α-detection at 4.2 K. Information on partial wave amplitudes as well as hyperfine interactions has been extracted.     

A study of 223Ra populated by α-decay

The low spin states of ²²³Ra have been populated via α-decay from ²²⁷Th which was itself produced following β⁻ decay of an ²²⁷Ac source. α–γ and α−e _K,L,M angular correlation measurements have been analysed using the correct ground state spins of ²²⁷Th(=1/2⁺) and ²²³Ra(=3/2⁺) for the first time. The analysis has allowed unique J^π values to be assigned to almost all levels below 400 keV excitation in ²²³Ra. Values of (g _K−g _R)/Q ₀ have been deduced for several members of the K= 3/2^± bands (for the first time in an odd N nucleus in this mass region) allowing estimates of g _K and g _R to be extracted. The values of g _K and g _R are not significantly different for the positive and negative parity band members and tend to support other strong evidence that stable octupole deformation exists in ²²³Ra at low excitation energies. Received: 17 November 1997 / Revised version: 8 January 1998