The decay of109gPd

The decay of 13·5 h^109gPd has been investigated using high resolution Ge(Li) singles -ray spectrometers and Ge(Li)-Ge(Li) coincidence technique. A total of 31 -rays of^109gPd was observed. The experimental K-conversion coefficients for 19 -transitions were determined. Detailed quantitative information on - coincidences was obtained. The decay scheme of^109gPd is presented.Authors wish to express thanks to Ing. A.Kuklík for the assistance in experimental apparatus arrangement and to Dr. J.Frána for providing of computer programs. Prof. I.Úlehla and Dr. J.Adam are acknowledged for usefull comments.     

Double-β decay of116Cd

The NEMO-2 tracking detector located in the Fréjus Underground Laboratory was designed as a prototype of the detector NEMO-3 to study 0ν and 2ν double-beta decay (ββ) physics. After ten months of nearly continuous running with an enriched cadmium source (0.92 mol·y of¹¹⁶Cd) aββ2ν half-life ofT _1/2=(3.75±0.35(stat)±0.21(syst))·10¹⁹ y was measured. Limits with 90% CL on the¹¹⁶Cd half-lives of 5.0·10²¹ y forββ0ν decay and of 1.2·10²¹ y forββ0νχ ⁰ decay with a Majoron (χ ⁰) were obtained. Theoretical predictions for 0ν and 2ν decays of¹¹⁶Cd are also presented.     

The Gamow-Teller beta decay of100Cd

Neutron-deficient isotopes of cadmium were produced in thep(600 MeV)+^natSn spallation reaction. The ISOLDE facility provided mass-separated beams of these isotopes. The production yield was 10³ to 10⁴ atoms/s for¹⁰⁰Cd and roughly two orders of magnitude less for⁹⁸Cd. The properties of the¹⁰⁰Cd→¹⁰⁰Ag decay were studied in detail by X-ray,γ-ray and conversion electron spectroscopy. Forty nineγ-transitions were assigned to this decay, and all but five of them were placed in the decay scheme. The half-life was determined to be 49.1±0.5 s. TheQ _EC value of 3890±70 keV was deduced from a comparison of experimental and theoreticalβ ⁺/(EC+β ⁺ probability ratios. Seven 0⁺→1⁺ Gamow-Teller transitions with log ft values between 3.5 and 4.9 were identified. The total (summed) strength is about five times smaller than predicted by the shell model for the transformation of ag _9/2 proton into ag _7/2 neutron. The quenching of the Gamow-Teller strength and other questions of nuclear structure are discussed for the¹⁰⁰Cd decay. The properties of⁹⁸Cd are inferred by extrapolation of^104,102,100Cd data, and some preliminary experimental results on⁹⁸Cd decay are presented.     

Nuclear level structure of low lying levels of109Cd

Nuclear level structure of low lying levels of¹⁰⁹Cd from¹⁰⁹In decay has been investigated by gamma-gamma angular correlation experiments using a Ge(Li)-NaI(Tl) fast coincidence arrangement. From the measurement on the 347.4?326.3, 347.4–650.1, 287.7–650.1, 203.3–420.5, 203.3–619.3 keV cascades spin-parity assignments of 5/2⁺,1/2⁺,7/2⁺,5/2⁺, 7/2⁺,5/2⁺,9/2⁺, and 9/2⁺, have been made to the ground, 59.5, 203.3, 347.4, 623.8, 673.7, 822.5 and 997.5 keV states, respectively, of¹⁰⁹Cd. The results have been discussed and compared with the previous works.     

The decay of110mAg to110Cd

The gamma-ray spectrum of the decay of^110mAg has been measured with the Ge(Li) detectors. A total of 32 gamma rays associated with the decay of^110mAg have been observed and their intensities determined. A number of gamma-ray transitions have not been observed previously. The K-electron internal conversion coefficients were found from the relative gamma intensities used in conjunction with published K-conversion electron intensities.It is proposed that the level scheme of¹¹⁰Cd has new levels at 1410·4, 1443·2 and 2237·7 keV in addition to the previously known levels. The spins and parities of the new levels are discussed.The author wishes to express her gratitude to Professor V. Petrílka for his permanent support and to Mr. J. Lipták and Mr. J. Vrzal for valuable assistance and discussions.     

Search for double beta decay of 106Cd

A search for the β⁺β⁺, β⁺/EC, and EC/EC decays of ¹⁰⁶Cd was performed at the Modane Underground Laboratory (France) located at a depth of 4800 m w.e. using a TGV-2 multidetector germanium spectrometer. A preliminary evaluation is performed of the experimental data accumulated during the measurements (12 900 h) of ～13.6 g of ¹⁰⁶Cd (with an enrichment of 75%) and the spectrometer background without samples and with samples of natural Cd. New limits (at a 90% confidence level) of half-lives are obtained: T _1/2 ? 1.7 × 10²⁰ yr and T _1/2 ? 1.6 × 10²⁰ yr for the 0νEC/EC resonant decay of ¹⁰⁶Cd to the 2741 keV and 2718 keV excited states of the daughter nucleus ¹⁰⁶Pd and T _1/2 ? 4.2 × 10²⁰ yr for the 2νEC/EC decay to the ground state of ¹⁰⁶Pd (0⁺ → 0⁺, g.s.). The limits for other branches of the double beta decay of ¹⁰⁶Cd with transitions to the ground and excited states of ¹⁰⁶Pd are improved.     

High-spin states in109Sn and their decay to the ground state

An extended level scheme of¹⁰⁹Sn is presented showing high-spin states up to E_x≈ 8 MeV and spins up toJπ=(41/2+). Their decay to the 5/2+ ground state has been observed identifying a 12.8 keV 7/2⁺ → 5/2⁺ transition. A half-life of T_1/2=7(1) ns has been measured for the 17/2⁺ state atE _x =2114 keV. The experimental data are compared with the predictions of shell-model calculations.     

Alpha decay of 109I and its implications for the proton decay of 105Sb and the astrophysical rapid proton-capture process

An alpha-decay branch of (1.4+/-0.4) x 10(-4) has been discovered in the decay of 109I, which predominantly decays via proton emission. The measured Q(alpha) value of 3918+/-21 keV allows the indirect determination of the Q value for proton emission from 105Sb of 356+/-22 keV, which is approximately of 130 keV more bound than previously reported. This result is relevant for the astrophysical rapid proton-capture process, which would terminate in the 105Sn(p,gamma)106Sb(p,gamma)107Te(alpha decay)103Sn cycle at the densities expected in explosive hydrogen burning scenarios, unless unusually strong pairing effects result in a 103Sn(p,gamma)104Sb(p,gamma)105Te(alpha decay)101Sn) cycle.     

Excited states in107Ag from the decay of107Cd

The decay of¹⁰⁷Cd has been studied with Ge(Li) and Si(Li) detectors. Thirty three gamma rays were observed in this decay of which nine for the first time. Gammagamma directional correlation techniques employing a Ge(Li)-NaI(Tl) system were used to determine spins and mixing ratios. A decay scheme has been constructed with firmly established excited states at 93.13(7/2⁺), 125.4(9/2⁺), 324.8(3/2^?), 423.0(5/2^?), 786.7(3/2^?), 922.1(5/2⁺), 949.7(5/2^?), 972.9(7/2^?, 5/2^?), 1143.0(5/2^?), 1223.0(5/2⁺), 1258.8(5/2^?), 1325.7(5/2^?) keV. A tentative level has been introduced at 1389.8(7/2⁺) keV. The results are compared with the predictions of the theoretical calculations of Paar [10].     

Gamow-Teller beta decay of the very neutron-deficientN=50 nuclide98Cd

For the first time, detailed decay-spectroscopic investigations were performed for the very neutron-deficientN=50 nuclide⁹⁸Cd. The⁹⁸Cd activity was produced in spallation reactions between 600 MeV protons and a natural tin target, yielding a⁹⁸Cd beam intensity of 10 to 60 atoms/s at the collector of the ISOLDE massseparator. By means of-ray and conversion-electron spectroscopy, 19 transitions were found to follow the ⁺/EC decay⁹⁸Cd⁹⁸Ag. The transitions at 61 and 107 keV were shown to beM1(+E2) andE2, respectively, and the⁹⁸Cd half-life was measured as 9.2±0.3 s. TheQ _EC value of⁹⁸Cd is determined semiempirically and is compared to model predictions together with the measuredQ _EC values of the neighbouring cadmium isotopes^100,102Cd and theN=50 isotones⁹²Mo,⁹⁴Ru, and⁹⁶Pd, taken from the literature. The newly established decay scheme of⁹⁸Cd includes 9 excited states of⁹⁸Ag. Four states at 1691, 1861, 2164, and 2544 keV are directly fed by 0⁺ 1⁺ Gamow-Teller beta transitions with a summed strength of 3.5 _–0.7 ^+0.8 . This value corresponds to 25±5% of the strength predicted for the GT transformation of a g_9/2 proton (in⁹⁸Cd) into a g_7/2 neutron (in⁹⁸Ag) by the extreme single-particle shell model. The GT-strength splitting and quenching, observed for⁹⁸Cd, are compared with the corresponding data for lighter even-even N=50 isotones, and are discussed with reference to the predictions of more sophisticated nuclear models. We find that only in some cases it is possible to explain qualitatively the observed GT strength distribution and its total magnitude without renormalizing the free-neutron value of the axial-vector coupling constant.Dedicated to Prof. P. Armbruster on the occasion of his 60th birthday     

Double-beta decay Q values of Cd and Te

The Q values of the ¹¹⁶Cd and ¹³⁰Te double-beta decaying nuclei were determined by using a Penning trap mass spectrometer. The new atomic mass difference between ¹¹⁶Cd and ¹¹⁶Sn of 2813.50(13) keV differs by 4.5 keV and is 30 times more precise than the previous value of 2809(4) keV. The new value for ¹³⁰Te, 2526.97(23) keV is close to the Canadian Penning trap value of 2527.01 ± 0.32 keV (Scielzo et al., 2009) [1], but differs from the Florida State University trap value of 2527.518 ± 0.013 keV (Redshaw et al., 2009) [2] by 0.55 keV (2σ). These values are sufficiently precise for ongoing neutrinoless double-beta decay searches in ¹¹⁶Cd and ¹³⁰Te. Hence, our Q values were used to compute accurate phase-space integrals for these double-beta decay nuclei. In addition, experimental two-neutrino double-beta decay nuclear matrix elements were determined and compared with the theoretical values. The neutrinoless double-beta decay half-lives for these nuclei were estimated using our precise phase-space integrals and considering the range of the best available matrix elements values.     

Analysis of decay data from neutron-rich nuclei

The β-decays of the neutron-rich nuclei ¹²Be and ²⁹Ne have been studied. The statistical correlations between the almost identical half-lives of ¹²Be and its daughter ¹²B are analysed for a large sample of ¹²Be decay data. Stringent mutual bounds are obtained on the parameter set, leading to a precise determination of the ¹²Be half-life of 21.50±0.04 ms. From a simultaneous detection of β-particles and neutrons from the decay of ²⁹Ne the neutron emission probability, P_n, is determined to 17±5%. No indication of two-neutron emission is seen from this nucleus. An upper limit of 2.2% (90% confidence level) is established for P_2n. Received: 3 May 2001 / Accepted: 6 August 2001     

Search for double- β decay processes in 108Cd and 114Cd with the help of the low-background CdWO 4 crystal scintillator

The lifetime of the recently discovered six-quasiparticle (6-qp) isomer in ¹⁴⁰Nd has been measured using the ¹²⁶Te(¹⁸O, 4n) reaction and the pulsed-beam technique at the Institut de Physique Nucléaire (IPN) Orsay. The deduced lifetime of the 6-qp isomer in ¹⁴⁰Nd of 1.23(7)μs supports the 20⁺ spin-parity assignment to the isomeric state which is based on a spherical configuration that coexists with the triaxial bands observed in this spin range. Evidence for delayed components for the transitions below the 19/2⁺ state in ¹³⁹Nd was observed, with an apparent half-life of 272(4)ns.     

Status of the INR experiment on 2β decay of Cd

Measurements of ¹¹⁶Cd double beta decay with help of enriched¹¹⁶CdWO₄ crystal scintillator are in progress in the Solotvina Underground Laboratory. The last part of the exposition with the background rate less than 0.6 counts/y·kg·keV (in the region of interest 2.7–2.9 MeV) is about 19000 hours. The half-life limit T1/2(0ν)≥3.2·10²² y (90% C.L.) is obtained for neutrinoless 2β decay of ¹¹⁶Cd. It corresponds to restrictions on the values of the neutrino mass m_ν≤3.9 eV, right-handed admixtures in weak interaction η≤5.7·10⁻⁸, λ5.0·10⁻⁶ and R-parity violating parameter of minimal supersymmetric standard model ≤1.1·10⁻³. For neutrinoless modes with emission of one and two Majorons, the limits T1/2(0νM1)≥1.2·10²¹ y and T1/2(0νM2)≥2.4·10²⁰ y (90% C.L.) are determined. To advance these results to a level of the limit m_ν≤1–2 eV, the improved set-up with four enriched ¹¹⁶CdWO₄ crystals is in mounting low.     

109Cd源激发的X射线荧光法无创伤测定人体骨铅含量

建立了用以体内测定骨铅含量的109Cd源作为激发源的X射线荧光测量系统. 该系统采用高纯锗探测器(10 mm×7 mm), 检测人体胫骨中铅被109Cd的88.0 keV的γ射线激发后产生的特征K层X射线. 采用铅的K层X射线对相干散射归一化的方法, 根据铅的K层X射线强度与相干散射强度的比值对胫骨模型铅含量之间的校正曲线, 便可得到人体骨铅的含量. 这种归一化的方法, 使测量结果的精确度不受骨外组织层厚度、骨的形状、大小、密度以及被测者位移的影响. 用含铅石膏制作的一组胫骨模型得到的校正曲线呈现良好的线性关系. 对急性铅中毒工人的试验性测量结果表明, 他们的骨铅含量明显高于对照组.     

Evidence for element 109 from one correlated decay sequence following the fusion of58Fe with209Bi

An experiment to synthesize element 109 is presented. Decay patterns characteristic of complete fusion products were searched for in an irradiation of²⁰⁹Bi targets with⁵⁸Fe projectiles at specific incident energies of 4.95, 5.05, and 5.15 MeV/u. A total dose of 7 ×10¹⁷ particles was obtained. The experimental method involves in-flight separation of forward peaked reaction products with a static-field velocity filter, their passage through a time-of-flight device and their final implantation into position sensitive solid state detectors to measure their kinetic energy, approximate mass and their time and position of incidence. The subsequent decay of the narrowly localised reaction products by cascades of alpha particles and/or spontaneous fission is also registered in terms of the energies and times of all the emitted particles. One outstanding decay sequence that started with the emission of two alpha particles within subsequent time intervals of 5 ms and 22 ms and ended with spontaneous fission after 13 s was found at 5.15 MeV/u. The first alpha particle had a kinetic energy of (11.10±0.04) MeV. A detailed analysis of all the alternative interpretations of this observation, such as a purely random correlation of signals, the decay of a product from a transfer reaction or of any of the various energetically possible evaporation residues, shows that the isotope with mass 266 of element 109, i.e. the one neutron evaporation channel after complete fusion, is the statistically most significant assignment. The outlook for new element synthesis is also briefly discussed.     

Determination of QCD condensates from τ decay data

We have used the latest data from the ALEPH Collaboration to extract values for QCD condensates up to dimension d=12 in the V-A channel and up to dimension d=8 in the V, A and V+A channels. Performing two- and three-parameter fits, we obtain new results for the correlations of condensates. The results are consistent and agree with most of the previous results found in the literature.