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.     

Identification of 180Pb

The α decay of the new isotope ¹⁸⁰Pb was observed in ⁴⁰Ca bombardments of ¹⁴⁴Sm: E _α = 7.23(4) MeV, and, \({T_{1/2}} = \left( {4_{ - 2}^{ + 4}} \right){\text{ ms}}\) . With this decay energy and the known mass of ¹⁷⁶Hg, the mass excess of ¹⁸⁰Pb was calculated to be ?1.98(5) MeV.     

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.     

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.     

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.     

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.     

Search for superdeformation in180Os

Two-dimensional γ-ray energy correlations have been measured at high spins in¹⁸⁰0s with the TESSA2 spectrometer. The E_γ ? E_γcorrelation matrix displays ridges characteristic of rotational bands with different energy separations of 96± and 72± keV for the energy regions of 660 to 840 keV and 975 to 1170 keV, respectively. The separation of these ridges remains constant in both energy regions. The dynamical moments of inertia are θ⁽²⁾ =83±3 and 111±5 ?²/MeV, respectively. The latter value suggests superdeformation in¹⁸⁰0s with an axis ratio c/a=1.76 (β₂ ?0.64) at high spins.     

Design of 180 °Vertical Viewing-angle Rainbow Hologram

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Properties of side bands observed in180Os

Bands in ¹⁸⁰ Os have been studied with in-beam spectroscopy methods. Four side bands were established. Configurations have been assigned to them considering the features of similar bands in neighbouring nuclei. New aspects result from an interpretation in the framework of the cranked shell model.     

Gamma deexcitation of the 180m Ta isomer

Vibrational states built on the K ^π = 9^? isomer and on the ground state (K ^π = 1⁺) in ¹⁸⁰Ta are calculated within the quasiparticle-phonon nuclear model using the ¹⁷⁸Hf nucleus as a core. A procedure for calculating the rates of K-allowed γ-ray transitions from vibrational states built on the isomer to those built on the ground state is presented. The probabilities of two-step processes consisting of a dipole excitation of the isomer and successive E1 and E2 transitions from them to vibrational states built on the ground state of the ¹⁸⁰Ta nucleus are calculated. Two-step transitions from the isomer to vibrational states below 2.7 MeV and to the vibrational states built on the ground state appear to be very weak. There are many E1 transitions from the vibrational states built on the isomer to the vibrational states built on the ground state. They are weak and cannot be responsible for the strong deexcitation of ^180m Ta in the relevant (γ, γ′) reaction. A decisive role is played by collective E2 transitions from dipole excitations in several excitation energy intervals ranging between 2.7 and 4.0 MeV. These highly intense K-allowed two-step γ-ray transitions can be responsible for the strong deexcitation of the ^180m Ta state in the (γ, γ′) reactions.