Identification of180Pb

Theα decay of the new isotope¹⁸⁰Pb was observed in⁴⁰Ca bombardments of¹⁴⁴Sm:E _α = 7.23(4)MeV, and,T _1/2=(4 _?2 ⁺⁴ )ms. With this decay energy and the known mass of¹⁷⁶Hg, the mass excess of¹⁸⁰Pb was calculated to be ?1.98(5)MeV.     

Spectroscopic Identification of Interactions of Pb2+ with Bovine Serum Albumin

The effect of Pb²⁺ targeted to bovine serum albumin (BSA) in vitro was investigated by fluorescence, synchronous fluorescence, UV absorption and circular dichroism (CD) spectrophotometry. The characteristic fluorescence of BSA was quenched, which indicated that Pb²⁺ changed the skeleton of BSA and caused the gradual exposure of aromatic amino acid residues (Trp, Tyr, Phe) in the internal hydrophobic region of BSA. When the concentration of Pb²⁺ was higher than 1 × 10⁻⁴ mol/L, the BSA was completely denatured. The excess lead ion interacted with the aromatic amino acid residues of BSA exposed to the solution, which decreased the fluorescence of BSA further. According to the experiment results, we found that a lead-BSA complex was formed following static quenching and the binding site was calculated approximately equal to 1. This work reflected the interaction mechanism of BSA and Pb²⁺ from the perspective of spectroscopy.     

The PbPb collision

The reaction ²⁰⁸Pb on ²⁰⁸Pb was studied at bombarding energies of 7.0 and 7.57 MeV/u. One-particle inclusive measurements using a large-area position-sensitive ionisation chamber delivered the kinetic energy, charge and scattering angle of the reaction products. A precise calibration of the stopping power for very heavy ions in the detector gas was performed. The measured Wilczynski diagrams show, for increasing loss of kinetic energy, an increase of the mean scattering angle. It is attributed to the dominance of the repulsive Coulomb forces with respect to the attractive nuclear forces. The element distribution for the ²⁰⁸Pb on ²³⁸U reaction at 7.5 MeV/u was also measured and compared to the PbPb and UU reactions. Fission probabilities are derived as a function of charge and total kinetic energy loss. The most striking result is seen in the σ_z² versus TKEL correlation: the average rate of energy loss per nucleon exchange is abnormally large. It is shown that this behaviour is associated with the double magic closed shell character of the colliding nuclei. Nuclear structure information is extracted through a simple parametrisation.     

Measurement of theβ-decay branch in180Lu to180m Hf for Investigation of the r-process nucleosynthesis of180m Ta

Theβ-decay branch of¹⁸⁰Lu to^180m Hf is measured by an integral method tracing the amount of^180m Hf daughter activity, to be 0.46 (15)%. Samples of¹⁸⁰Lu are prepared by on-line mass separation of¹³⁶Xe-on-tungsten transfer reaction products. The amount of isobaric^180m Hf in the samples is strongly suppressed by the employed separator ion source; its directly produced fraction is derived from comparison with^177m Hf activity. The properties of lutetium and hafnium release from the ion source are separately determined. With this measurementr-process nucleosynthesis is estimated to account for at most 22% of the solar^180m Ta abundance.     

High-frequency 180 GHz PELDOR

For aromatic organic radicals, pulsed electron-electron double resonance (PELDOR) experiments at high magnetic fields offer the possibility to achieve orientation-selective pumping and detection that could allow one not only to determine the distance between paramagnetic species but also their relative orientation with respect to the interconnecting dipolar axis. We present a PELDOR two-frequency setup that was introduced into our homebuilt 180 GHz pulsed electron paramagnetic resonance (EPR) spectrometer and we discuss its technical and experimental features. The capability of 180 GHz PELDOR has been tested using the three-pulse ELDOR sequence on the protein RNR-R2 (ribonucleotide reductase) fromEscherichia coli, which contains two tyrosyl radicals at a distance of 3.3 nm. At 180 GHz, orientation selectivity is observed and the modulation frequency was found in good agreement with theoretical predictions, which take into account the relative orientation of the radicals from X-ray data.     

K-X-ray spectrum of the Pb + Pb quasimolecules

We present ab initio calculations of the quasimolecular K-X-ray spectrum from the Pb + Pb system, where both the Kd-hole amplitude and the radiation amplitude is calculated in first order perturbation theory. A comparison with the background radiation like NNB, SEB and γ-decay of excited nuclei shows that the molecular X-rays should be measurable up to X-ray energies corresponding to the characteristic K-line of the united superheavy atom.     

Theg-factor of the 2+ state of180W and quadrupole moment ratios observed for180W and180Hf by the Mössbauer technique

By Mössbauer absorption experiments the magnetic hyperfine splitting has been observed for the 2+ states of¹⁸⁰W and¹⁸²W in a tungsten iron alloy (3.6 at%W). Since theg-factor of the 2+ state of¹⁸²W is known the measured splitting of the¹⁸²W line could be used for the calibration of the magnetic hyperfine field and the measurement with¹⁸⁰W gave then for the unknowng ₂₊-factor of¹⁸⁰W: $$g_{2 + } (^{180} W) = 0.260 \pm 0.017.$$ By use of a WO₃ absorber the electric quadrupole splittings in the same states were measured. The ratio of the quadrupole moments was derived $$\frac{{Q_{2 + } (^{180} W)}}{{Q_{2 + } (^{182} W)}} = 0.983 \pm 0.022.$$ This ratio is somewhat smaller, but more accurate than the weighted means of previous results and in disagreement with the theoretical prediction. A similar measurement with¹⁷⁸Hf and¹⁸⁰Hf and a HfO₂ absorber gave $$\frac{{Q_{2 + } (^{178} Hf)}}{{Q_{2 + } (^{180} Hf)}} = 1.052 \pm 0.021.$$ This result is larger than the average of previous measurements and agrees with theory. The isomer shifts of the Mössbauer lines of¹⁸⁰W and¹⁸²W were measured for sources in a tantalum metal environment and for absorbers of metallic tungsten. Different signs were observed which indicate that the mean squared charge radius of the 2+ state of¹⁸²W is larger than that of the ground state whereas for¹⁸⁰W the ground state has the larger 〈r ²〉-value.     

Superconductivity of Pb films studied with superconducting Pb tips

<正>Studying the superconductivity of materials using scanning tunneling microscopy (STM) remains a challenge to this day[1]. In this regard, the stability of the tunneling junction is a critical factor, together with the spectroscopy resolution.Using a superconducting tip is an effective way to increase the resolution of the obtained tunneling spectra [2-6]. For example, Pan et al.[2] showed that the use of super-     

Isomeric states in180Os

Two new isomers have been observed in¹⁸⁰Os. A high-K isomer withI, K ≧20 and a half-life ofT _1/2=12+4 ns have been established. It deexcites via two transitions into the 18⁺ level of the yrare band indicating an unusually smallK-hindrance factor. Evidence for an isomer withI, K>16 and a half-life ofT _1/2=41±10 ns was found. A half-life of 17±3 ns was measured for the previously known 7^? state at 1862 keV. The decay scheme of the previously known 7^? isomer at 1928 keV has been extended and a revised version is presented.     

The decay of the new isotope180Yb and the search for ther-Process path to180mTa

Irradiating^natW/Ta targets with¹⁸⁶W, the decay of the new isotope¹⁸⁰Yb was observed and its half-life determined to be 2.4(5) min. Based on the measuredβ-,γ- and X-ray data, ther-process production of^180mTa and the role of a possible isomer^180mLu in this context are discussed.     

Selective observation of continuum transitions in the Pb+Pb quasimolecule

Cross sections for doubleK shell excitation and for the production of continuum x-rays in coincidence withK x-rays from 4.8 MeV/amu²⁰⁸Pb +²⁰⁸Pb collisions have been measured. A simple statistical model is presented to explain double vacancy contributions to the coincidence cross sections and the relative contributions of MO x-ray,K x-ray cascade and MO x-ray,K x-ray double vacancy coincidences are evaluated. These latter yields are found to be significant enough to make extraction of the cascade contribution to the measured coincidence yields problematic.     

180° -turns in integrated optics

Integrated optic devices, such as directional couplers, typically have a length to width ratio of 1:1000. Therefore economical use of quadratic substrate areas requires 180° wave guide turns to cover the whole substrate with a complex circuit in a zick-zack manner. For 180° -turns only curved guides have been considered. Radii of > 1 cm are necessary to avoid loss, and therefore are useless. A new concept for 180° -turns is proposed consisting of a halved 3 stage Δβ-reversal coupler with mirrors at one end. It is demonstrated that these 180° -turns may be fabricated providing high efficiency.