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Studies of the chemical property of transactinide elements are very difficult due to their short half-lives and extremely small production yields. However it is still possible to obtain considerable information about their chemical properties, such as the most stable oxidation states in aqueous solution, complexing ability, etc., comparing their behaviour with their lighter homologous in the periodic table. In order to obtain a better knowledge of the behavior of rutherfordium, Rf (element 104), dubnium, Db (element 105) in HF medium, the sorption properties of Zr, Hf, Nb, Ta and Pa, homologues of Rf and Db, were studied in NH4F/HClO4 medium in this work. Stability constants of the fluoride complexes of these elements were experimentally obtained from Kd obtained at different F- and H+ concentrations. The anionic complexes: [Zr(Hf)F5]-, [Zr(Hf)F6]2-, [Zr(Hf)F7]3-, [Ta(Pa)F6]-, [Ta(Pa)F7]2-, [Ta(Pa)F8]3-, [NbOF4]- and [NbOF5]2- are present as predominant species in the HF range over investigation.

Summary A chemical separation procedure for Rf/Db is described which was applied to a long-lived decay product from the nuclear fusion reaction 48Ca+ 243Am. A 1.2 mg thick 243Am target was bombarded by 247 MeV 48Ca particles. The recoiling products were collected in a thick Cu catcher for about one day and then subjected to a chemical separation procedure that included an ion exchange from dilute HF solutions. Final samples were prepared on 30 μg/cm2 thick polyethylene (PE) foils and counted in 4π-geometry for α-particles and spontaneous fission (SF) coincidences. The detector arrays were surrounded by 3He detectors to also assay prompt neutrons. Decontamination factors from actinides of about 105 were achieved. Group 6 (W) to 14 (Pb) elements as models for their heavier homologues were shown to be separated from the Rf/Db fraction with more than 90%. In eight final samples, representing a total beam dose of 3.4 × 1018 particles, 15 SF events were detected. The decay pattern points to a single component with a half-life of ≈32h, which shows a chemical behavior similar to the lighter homologues of group 4 and 5 elements.

Experiments aimed at detecting and investigating neutron resonances in the $$^{178m_2 } Hf$$ isomer are described, and the results obtained in these experiments are presented. The investigations in question are of great interest since the structure of this isomer—it is interpreted as the (π7/2+, π9/2+, ν7/2+, ν9/2+) configuration—and its high spin of J=16 differ significantly from the structure and spin of nuclei studied previously. The experiments performed at the Kurchatov Institute employed a neutron source based on the FAKEL linear electron accelerator and a multisection detector from NaI(Tl) crystals that was able to ensure a 4π coverage. This equipment made it possible to study gamma-ray cascades in radiative neutron capture versus neutron energy. Despite an extremely small number of isomer nuclei, a low content of the isomer in the target used, and its high radioactivity, resonances were discovered that arise upon neutron capture by a high-spin $$^{178m_2 } Hf$$ nucleus. The parameters of these resonances were found. The mean spacing between the revealed resonances is about 1 eV, which is consistent with calculations based on the Fermi gas model. This indicates that the Fermi gas model describes well the density of both low-and high-spin levels. At the same time, the above agreement suggests that, upon the formation of a compound nucleus, the structure of the isomeric state is destroyed completely. On the other hand, glaring discrepancies between experimental data and the predictions of the statistical model were found: gamma transitions from high-spin resonances (J=31/2+, 33/2+) populate predominantly the low-spin ground state (J=9/2+) rather than the high-spin state of the $$^{178m_2 } Hf$$ isomer (J=25/2−); the radiative width is approximately one-third as great as that which is predicted by the statistical model; and the properties of gamma cascades are different for different resonances, this difference being beyond statistical fluctuations. The results of the present investigation make it possible to reveal special features in the behavior of the quantum number K at high excitation energies.

We summarize here the results of the TARC experiment whose main purpose is to demonstrate the possibility of using Adiabatic Resonance Crossing (ARC) to destroy efficiently Long-Lived Fission Fragments (LLFFs) in accelerator-driven systems and to validate a new simulation developed in the framework of the Energy Amplifier programme. An experimental set-up was installed in a CERN PS proton beam line to study how neutrons produced by spallation at relatively high energy ( E n ⩾1 MeV ) slow down quasi-adiabatically with almost flat isolethargic energy distribution and reach the capture resonance energy of an element to be transmuted where they will have a high probability of being captured. Precision measurements of energy and space distributions of spallation neutrons (using 2.5 and 3.5 GeV/c protons) slowing down in a 3.3 m×3.3 m×3 m lead volume and of neutron capture rates on LLFFs 99Tc, 129I, and several other elements were performed. An appropriate formalism and appropriate computational tools necessary for the analysis and understanding of the data were developed and validated in detail. Our direct experimental observation of ARC demonstrates the possibility to destroy, in a parasitic mode, outside the Energy Amplifier core, large amounts of 99Tc or 129I at a rate exceeding the production rate, thereby making it practical to reduce correspondingly the existing stockpile of LLFFs. In addition, TARC opens up new possibilities for radioactive isotope production as an alternative to nuclear reactors, in particular for medical applications, as well as new possibilities for neutron research and industrial applications.

The branching ratio of $^{225}$Ac decay by emission of $^{14}$C was remeasured under improved experimental conditions by using a radioactive source produced at the ISOLDE mass-separator at CERN and a nuclear track detector technique. The result, B=$\lambda_{^{14}\textrm{C}} / \lambda_{\alpha} = (4.5 \pm 1.4) 10^{-12}$, is consistent with the anomalously high value obtained in the 1993 experiment thus confirming the importance of nuclear structure effects in this exotic decay.

The Transmutation by Adiabatic Resonance Crossing (TARC) experiment was carried out as PS211 at the CERN PS from 1996 to 1999. Energy and space distributions of spallation neutrons (produced by 2.5 and 3.57 GeV/c CERN proton beams) slowing down in a 3.3×3.3×3 m3 lead volume and neutron capture rates on long-lived fission fragments 99Tc and 129I demonstrate that Adiabatic Resonance Crossing (ARC) can be used to eliminate efficiently such nuclear waste and validate innovative simulation.

We have measured the cross section of the 7Be(p,gamma)8B reaction for E_cm = 185.8 keV, 134.7 keV and 111.7 keV using a radioactive 7Be target (132 mCi). Single and coincidence spectra of beta^+ and alpha particles from 8B and 8Be^* decay, respectively, were measured using a large acceptance spectrometer. The zero energy S factor inferred from these data is 18.5 +/- 2.4 eV b and a weighted mean value of 18.8 +/- 1.7 eV b (theoretical uncertainty included) is deduced when combining this value with our previous results at higher energies. Comment: Accepted for publication in Phys. Rev. Lett

By using glass track detectors in 4π geometry we measured the branching ratio of 230 U for emission of Ne clusters to be B=(4.8±2.0)×10 −14 and an upper limit for 18 O emission from 226 Th to be B −14 . On the basis of theoretical calculations, the most probable neon cluster comes out to be 22 Ne.

The effect α particle fluences ( 3 × 10 3 −2 × 10 15 cm −2 ) on properties of the two types of phosphate glass detectors with different compositions was studied. It was shown that the registration properties of glass detectors depended on the α particle fluence, spatial distribution of the α particle paths, and glass type. The critical α particle fluences, above which the detector properties changed, were determined.

Sorption properties of Zr, Hf, Nb, Ta and Pa at trace level towards a macroporous anion exchanger in HF–HCl media were investigated with two ion exchange methods: static (batch technique) and dynamic (column chromatography using the elution mode). Variations of the distribution coefficients as a function of HCl and HF concentration in the range 0.02–0.8 M for both acids are presented in the form of contour plots. Some of the most promising separation possibilities are pointed out.

Cross sections for the ${}^{7}\mathrm{Be}(p,\ensuremath{\gamma}{)}^{8}\mathrm{B}$ reaction have been measured for ${E}_{\mathrm{c}.\mathrm{m}.}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.35--1.4\mathrm{MeV}$ using radioactive ${}^{7}\mathrm{Be}$ targets. Two independent measurements carried out with different beam conditions, different targets, and detectors are in excellent agreement. A statistical comparison of these measurements with previous results leads to a restricted set of consistent data. The deduced zero-energy $S$ factor $S(0)$ is found to be 15%--20% smaller than the previously recommended value. This implies a ${}^{8}\mathrm{B}$ solar neutrino flux lower than previously predicted in various standard solar models.

The results of the investigation of some properties of polyethyleneterephtalate, phosphate glass and mica for the study of cluster decay and spontaneous fission of heavy nuclei are given. The investigation results of 230 U cluster decay and 226 Ra spontaneous fission investigation are presented. The probability of 230 U cluster decay in relation to α-decay is less than 7.5·10 14 . The partial half-life of 226 Ra spontaneous fission is more than 6.6·10 17 yrs. The fusion-fission cross sections for the ( 208 Pb + 16 O → 224 Th ) reaction, as the inverse reaction of cluster decay, in the subbarrier region of ion energy was measured. For the energies of 78, 75, 73 and 68 MeV 16 O (lab.system) the cross-sections are 7.8; 3.7·10 −2 , 8.5·10 −4 and 6·10 −6 mb, respectively.

The hyperfine structure and isotope shifts of the transition between the 5d6s2 a2D3/2 ground state and the 5d6s(a3D)6p z4F5/2 ° excited state of singly ionized hafnium at \lambda=340 nm have been investigated by laser spectroscopy using a radio-frequency quadrupole ion trap. The magnetic dipole coupling constant A and electric quadrupole coupling constant B of the two atomic levels for both stable isotopes 177Hf and 179Hf are determined. The changes of mean square nuclear charge radii \delta[ r2] of the stable Hf isotopes and the radioactive isotope 172Hf (T1/2=1.87a) have been extracted from the data.

Neutron activation analysis has been applied to determine the purity of super-enriched176Yb as well as a diagnostic to optimize yields from the P.A.R.I.S. mass separator at Orsay. In 25 mass separations carried out during 3 months, 910 mg of super-enriched176Yb2O3 were recovered from the original 7 g of176Yb2O3 (97.5% enrichment). Neutron activation analysis has shown that only two per thousand of the initially present174Yb remained in the super-enriched product. Using this176Yb super-enriched (99.998%) target, micro-quantities of the high spin (16+) isomer178m2Hf were produced by the (α,2n) reaction at the U-200 cyclotron in Dubna. Quantities of about 2·1012 atoms of this isomer have been irradiated by thermal neutron at the ORPHEE Reactor, Saclay. Only the neutron capture giving rise to the isomeric state 25/2− of179Hf has been measured, by detection γ-rays of this 25.1 days isomer. A cross section of 45±5 barns was obtained for178m2Hf(n,γ)179m2Hf.

The 178m2Hf with its long-lived (T1/2=31 y), high-spin Iπ = 16+, isomeric state, is a challenge for new and exotic nuclear physics studies. The 178m2Hf isomer has been produced in microweight quantities using the 176Yb(α,2n) nuclear reaction, by irradiation with a high-intensity beam using the U-200 cyclotron in Dubna. Radiochemistry and mass separation methods have been developed, with the aim to separate and purify the produced Hf material. Thin targets of isomeric hafnium-178 on carbon backings have been prepared and used in experiments with neutron, proton and deuteron beams.

Nowadays large interest is attached to the production of exotic beams and targets for nuclear structure and reaction studies. The nucleus178Hf, with is long-lived (T1/2=31 years) high-spin isomeric statelπ=16+ at a relatively low-excitation energy (2.446 MeV), is indeed a unique probe for studying phenomena in a new way. A wide research program has been underway in the framework of the “Hafnium Collaboration” which now concems around 80 scientists. Various targets have been prepared and adapted to different types of experiments. Irradiation processes with high-intensity beams, high-purity chemistry methods and isotopic separations have been developed. The obtaining of appreciable amounts of very high purity178m2Hf by isotopic separation, has made it possible for us to carry out γ-ray measurements with good statistics and high energy resolution with a γ-spectrometer, in order to use this isomer as a calibration standard in the 200 to 600 ke V energy range. For example, relative to the main γ-rays, energies have been determined with an absolute uncertainty of about 2 e V and photon emission probabilities with a relative uncertainty better than 1%.

Photonuclear reactions on isomeric and ground state Hf and Ta targets were studied systematically by activation technique. The reaction yields were measured and isomer-to-ground state ratiosY m /Y g were deduced. The systematics of theY m /Y g values versus spin difference of initial and final states in the photonuclear reaction shows that the structure selectivity for the population of the levels does not survive at high excitation energies.

In order to study the chemical properties of element 106 in aqueous media, fast, efficient and reproducible chromatographic separations were tested on its assumed homologues: Mo, W and U. Corroborative static and dynamic off-line experiments have shown that after fixation of these three elements on an anion-exchange resin in HF medium, selective elution could be achieved by using suitable concentrations of HCl-HF and HCl solutions. Separations of short-lived W isotopes, produced through heavy ion irradiation were also performed on-line.

The behaviour of the elements Zr, Hf, Nb, Ta and Pa has been investigated on macroporous anion exchange resin BIORAD AGMP 1 in HF medium (from 0.02 to 2M). All the studied elements show strong adsorption properties at low HF concentration. The adsorption was found to be highly dependent on H+ and F− concentrations. The distribution of possible adsorbable complexes is discussed.

Laser spectroscopy has been carried out on a sample of radioactive 172Hf ions in a Paul trap. Laser excitation is on the 5d6s2(a2D) (J = 3 2 )− 5d6s(a 3 D)6p(z 4 F) (J = 5 2 ) transition in the Hf ion (λ = 340 nm). The fluorescence is observed on the transitions to the two low lying metastable states 5d6s 2 (a 2 D) (J = 5 2 ) and 5d 2 (a 3 F)6s(a 4 F) (J = 3 2 ) . The spectra show besides the signal from 172Hf, contaminant signals from stable isotopes present in the sample. Hyperfine lines from the odd-A Hf isotopes are suppressed by light induced isotope selective HfH+ formation involving the H2 buffer gas used for cooling and quenching. The molecule formation leads to an effective loss of those isotopes in the sample and allows a better isolation of the weak signal from 172Hf. The HfH+ formation is from one of the metastable states (mainly 5d26s) which are populated after excitation to the 5d6s(a 3 D)6p(z 4 F) (J = 5 2 ) state. The molecule formation channel competes with the decay of the metastable states to the ground state through collisional quenching with the H2 buffer gas. The ratio between HfH+ formation and quenching probability is evaluated to be of the order of 10−5.

A heavy-ion multiple Coulomb excitation experiment on a very exotic target containing microweight quantities of 178Hf in the Kπn = 16+ isomeric state has been performed at 4.77 MeV/u 208Pb beam energy. The first excited Iπ = 17+ state has been observed at an excitation energy of 357.4 ± 0.3 keV with respect to the isomeric state. The intrinsic electric quadrupole moment of Q0 = 8.2 ± 1.1 b has been derived from the experimental data within the rigid rotor model.

In inelastic scattering of 22 MeV deuterons from an isotope-separated target of $^{178}\mathrm{Hf}$ containing about 2\ifmmode\times\else\texttimes\fi{}${10}^{13}$ nuclei in the isomeric ${16}^{+}$ state we observed rotational excitation to the ${17}^{+}$ state at an excitation energy with respect to the isomeric state of 356.5\ifmmode\pm\else\textpm\fi{}0.4 keV and weak evidence for the ${18}^{+}$ state at 737\ifmmode\pm\else\textpm\fi{}2 keV. We compared the differential cross sections with coupled-channel calculations and with scattering from $^{178}\mathrm{Hf}$ (${0}^{+}$) and $^{177}\mathrm{Hf}$ (7/${2}^{\mathrm{\ensuremath{-}}}$). \textcopyright{} 1996 The American Physical Society.

Some short-lived isotopes of Hf, Ta and W, synthesized at the U-400 cyclotron of JINR-Dubna, have been isolated using a previously elaborated fast continuous method of chemical isolation of element 104 from nuclear reaction products. The products were transported by a NaCl aerosol jet, from the irradiated targets to a separation device in which Hf, Ta and W were isolated by using three coupled ion-exchange columns.

An already existing, sub-critical arrangement made of natural uranium and water moderator has been exposed to a low intensity (≈ 109 ppp) proton beam from CERN-PS at several kinetic energies from 600 MeV to 2.75 GeV. The energy delivered by the hadronic cascade induced by the beam in the device has been measured by the temperature rise of small sampling blocks of uranium located in several different positions inside the device and counting the fissions in thin probe foils of natural uranium. We find typically G ≈ 30 in reasonable agreement with calculations, where G is the ratio of the energy produced in the device to the energy delivered by the beam. This result opens the way to the realisation of the so-called Energy Amplifier, a practical device to produce energy from thorium or depleted uranium targets exposed to an intense high energy proton beam. Results show that the optimal kinetic is ≥ 1 GeV, below which G decreases but is still acceptable in the energy range explored

The γ-spectrum following the α-decay of 236Pu was reinvestigated using a high resolution HPGe detector. The energy and intensity of 26 γ-transitions were measured accurately; 21 of these were observed for the first time. All γ-rays were placed in a 232U level scheme accounting for 13 levels of which 8 are reported for the first time. The ground state rotational band was found to be fed up to spin Iπ=8+ and the Kπ=0− octupole band to be fed up to I=5.

The short-lived isotopes of W and their descendants have been isolated from the products of the bombardment of144Sm with24Mg by a fast continuous ion-exchange method, using HF solution media. The feasibility of this method for isolation of element 106 is discussed.

A back-to-back ionisation chamber has been used to measure the fission fragment mass-kinetic-energy correlations for 248 Cm(s, f). In all about 12 × 10 6 fission events were collected. The different distributions in the high-yield region are consistent with the existent data. As predicted by the theory of fission channels, the existence of far-out asymmetric fission has been confirmed, but its amplitude is much smaller than that for 252 Cf(s, f) indicating that the barrier of the channel corresponding to this channel should be lower for 252 Cf(s, f) than for 248 Cm(s, f). Furthermore, the 〈 E K 〉( M H ) and σ E K ( M H ) distributions show correlated fluctuations in the far-out asymmetric region suggesting the existence of at least two scission configurations with different deformations for the same fragmentation. In the cold-fission region, the deformed neutron N ⋍ 88 shell dominates the yield.

The $^{223}\mathrm{Fr}$ \ensuremath{\beta} decay was reinvestigated using high-resolution single \ensuremath{\gamma} spectrometry as well as \ensuremath{\gamma}-\ensuremath{\gamma} coincidence techniques. For single \ensuremath{\gamma}-spectra measurements, radiochemically pure $^{223}\mathrm{Fr}$ sources were obtained by chromatographic separation from a 75 MBq activity $^{227}\mathrm{Ac}$ parent source and continuously purified of $^{223}\mathrm{Ra}$ and daughters. The analysis of the \ensuremath{\gamma} spectra of 30 sources showed the existence of 131 \ensuremath{\gamma} lines, of which 87 are reported for the first time in the $^{223}\mathrm{Fr}$ \ensuremath{\beta} decay although many of them are observed following the $^{227}\mathrm{Th}$ \ensuremath{\alpha} decay. The $^{223}\mathrm{Fr}$ half-life was remeasured and found to be ${\mathit{T}}_{1/2}$=22.00\ifmmode\pm\else\textpm\fi{}0.07 min. \ensuremath{\gamma}-\ensuremath{\gamma}-t coincidence measurements were also carried out with $^{223}\mathrm{Fr}$ purified sources. The $^{223}\mathrm{Ra}$ level scheme was built on the basis of our \ensuremath{\gamma} data, as well as $^{227}\mathrm{Th}$ \ensuremath{\alpha}-decay data. Among the 32 excited $^{223}\mathrm{Ra}$ levels, of which 22 were also known from $^{227}\mathrm{Th}$ \ensuremath{\alpha} decay, 13 are newly reported from $^{223}\mathrm{Fr}$ \ensuremath{\beta} decay. Low energy levels (E400 keV) may be classified as parity doublet bands according to the predictions of the reflection asymmetric rotor model. Above a 700 keV gap, a coexistence of symmetric and asymmetric shapes including both static and dynamic octupole correlations is suggested.

233U α-decay was reinvestigated using a radiochemically purified source and high efficiency HPGe coaxial detectors; the lowenergy γ-spectrum was also measured using a LEPS detector. The energy and intensity values of one hundred sixty three γ-lines were determined, from which forty eight are newly reported with respect to the last study of Canty et al. A revised229Th level scheme was built, using the Ritz combination principle, in which nine levels are newly observed, at 371.3, 381.8, 465.5, 569.2, 584.9, 605.1, 620.8, 656.9 and 749.9 keV.

The nucleus 178Hf, with its long-lived (T1/2=31 y) high-spin isomeric state Ipi =16+, is a challenge for new and exotic nuclear physics studies. The authors describe the first experiments they have performed in order to produce a reasonable microweight quantity of this hafnium isomer with an isomeric to ground-state ratio as high as possible (here 5%). The reaction 176Yb (4He, 2n) using an enriched target has been studied by measuring the excitation functions and the isomeric to ground-state ratio. About 3*1014 isomeric atoms have been produced up to now in irradiations with high-intensity beams ( approximately=100 mu A) at the U-200 cyclotron in Dubna. Chemical separation methods could be checked using about 1013 atoms of the isomer. Isotopic separation experiments have been performed in Orsay and preliminary results are given for the separation efficiency.

The {sup 14}C decay of {sup 222}Ra has been reinvestigated, using an 85 MBq activity {sup 230}U source radiochemically separated, a Si barrier detector, and a superconducting magnetic spectrometer. In a 16 days counting run, 210 {sup 14}C events were recorded. The {sup 14}C particles energy value 30.930{plus minus}0.090 MeV was found and an upper limit {ital b}{le}2{times}10{sup {minus}12} was estimated for the {sup 14}C branching ratio to the {sup 208}Pb first excited state; the branching-ratio value to the {sup 208}Pb ground state, thus equal to the total branching ratio, was found to be {ital b}={lambda}{sub {ital c}}/{lambda}{sub {alpha}}=(2.31{plus minus}0.31){times}10{sup {minus}10}.

The α-decay of225Ac to221Fr excited states has been reinvestigated using high-resolution γ-spectroscopy for single and γ-γ coincidence measurements. Twenty nine221Fr nuclear excited states were proposed; ten of which are newly observed.

The decay of a225Ac source in equilibrium mixture with its decay products was investigated using high-resolution HP/Ge/ detectors. Energies and intensities of more than 78 γ-photons were measured with an improved accuracy; 44 of them are reported for the first time. A tentative221Fr level scheme was built on the basis of good energy sum relationships; seven new221Fr excited levels are proposed at 496.9, 570.9, 603.5, 630.7, 637.7, 649.0 and 758.9 keV.

The results of two experiments designed to synthesize element 115 isotopes in the {sup 243}Am+{sup 48}Ca reaction are presented. Two new elements with atomic numbers 113 and 115 were observed for the first time. With 248-MeV {sup 48}Ca projectiles, we observed three similar decay chains consisting of five consecutive {alpha} decays, all detected in a total time interval of 30 s. Each chain was terminated by a spontaneous fission (SF) with a high-energy release and a lifetime of about a day. With 253-MeV {sup 48}Ca projectiles, we registered a different decay chain of consecutive {alpha} decays detected in a time interval of 0.5 s, also terminated by spontaneous fission, but after 1.8 h. The decay properties of the eleven new {alpha}- and SF-decaying nuclei are consistent with expectations for consecutive {alpha} decays originating from the parent isotopes {sup 288}115 and {sup 287}115, produced in the 3n- and 4n-evaporation channels, respectively. Support for the assignment of the atomic numbers of all of the nuclei in the {sup 288}115 decay chain was obtained in an independent experiment in which a long-lived spontaneous fission activity, {sup 268}Db (15 events), was found to be chemically consistent with the fifth group of the periodic table.more » The odd-odd isotope {sup 288}115 was observed with largest cross section of about 4 pb. In the SF decay of {sup 268}Db, a total kinetic energy of 230 MeV and a neutron multiplicity per fission of 4.2 were measured. The decay properties of the 11 new isotopes with Z=105-115 and the production cross sections are in agreement with modern concepts of the role of nuclear shells in the stability of superheavy nuclei. The experiments were carried out at the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research.« less

SummaryThe isotope262Db was produced by irradiation of a248Cm target with 106-MeV19F ions at the 15 MV MP Tandem accelerator of Orsay (France). The reaction products were continuously and rapidly transported with a KCl aerosol helium jet system to the chemistry setup. They were dissolved in HF medium and the solution was passed through three successive ion exchange columns, allowing a continuous high level purification of Db from actinides on a first cation exchange column, the isolation of Db on an anion exchange one, and the retention of the long-lived decay products of262Db (3.24 h–254Fm) on a second cation exchange column. Just after the end of irradiation, the decay products were desorbed from this column, purified and α-sources were prepared on carbon foil by electrospray. In 13 effective irradiation hours, 22 events corresponding to the α-decay of254Fm were recorded. Almost 70 atoms of262Db, produced in the reaction248Cm +19F were isolated in dilute HF medium. Like its homologues/analogues Nb, Ta and Pa, dubnium forms, with fluoride ions, negatively charged complexes which are strongly retained on anion exchanger.

The availability of a target of $^{178}\mathrm{Hf}$ in its aligned four-quasiparticle, ${\mathit{J}}^{\mathrm{\ensuremath{\pi}}}$=${16}^{+}$ isomeric state, has allowed to measure the effect of blocking of the aligned-quasineutron orbitals in the (p,t) reaction. The experimental ratio of cross sections R=${\mathrm{\ensuremath{\sigma}}}_{(16}^{+}$\ensuremath{\rightarrow}${16}^{+}$)/${\mathrm{\ensuremath{\sigma}}}_{(0}^{+}$\ensuremath{\rightarrow}${0}^{+}$) agrees with a predicted value deduced from the known (p,t) cross section on odd Hf isotopes.

We have measured the cross section of the 7Be(p,gamma)8B reaction for E(c.m.) = 185.8, 134.7, and 111.7 keV using a radioactive 7Be target (132 mCi). Single and coincidence spectra of beta+ and alpha particles from 8B and 8Be* decay, respectively, were measured using a large acceptance spectrometer. The zero energy S factor inferred from these data is 18.5+/-2.4 eV b and a weighted mean value of 18.8+/-1.7 eV b (theoretical uncertainty included) is deduced when combining this value with our previous results at higher energies.

This paper presents a QPSK modulator equipment designed and qualified for space applications. It enables high data rate transmission for Earth observation satellites. The equipment is based on a full MMIC RF chain, including a MMIC QPSK linear vector modulator, and features a direct X band Local oscillator (LO). Data rates up to 2×150 Mbits/s and RF output power up to 6 W for LO frequencies between 7.2 and 8.5 GHz can be achieved. Design description and Qualification Model performances are provided in this paper.

The electron-capture decay of the ${}^{168}{\mathrm{Lu}}^{m}$ ${(T}_{1/2}=6.7 \mathrm{min},$ ${J}^{\ensuremath{\pi}}{=3}^{+})$ isomer was studied with high purity sources, obtained by using a new radiochemical method consisting of fast continous on-line separation of reaction products. A complex spectrum composed of about 200 $\ensuremath{\gamma}$ rays was observed. From these, 162 transitions were assigned to a level scheme of 39 excited levels of ${}^{168}\mathrm{Yb}$, primarily by $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidence spectroscopic measurements. About 60 transitions were placed for the first time and $g90%$ of the decay intensity was clearly identified. The structure of the levels directly fed by the electron-capture decay was reviewed as particle-hole excitations of the core.

The low hindrance factors observed in the 14C decay of 223Ra to the 209Pb excited states at 779 and 1423 keV are interpreted as a consequence of the similitude of the wavefunctions describing the uncoupled neutron in 223Ra, Omega =3/2 (3/2(631)(X)3/2(761)), and in the first two excited states of 209Pb, namely the 1i11/2 and 1j15/2 shell model orbits.