New isotope159Lu and decay of158Lu,159,158Yb isotopes

Lutetium and ytterbium isotopes with masses A=159,158 have been produced by proton induced spallation reaction, and investigated by on-line mass separation and subsequent decay spectroscopy. A new isotope¹⁵⁹Lu (T_1/2=12.3±1 s) has been identified, and newγ-ray data have been obtained for the decay of¹⁵⁸Lu and^{159, 158}Yb.     

Messung des Elektroneneinfangs am Kern176m Lu

The electron capture of^176m Lu to the ground state and to the first excited state of¹⁷⁶Yb has been observed by measuring the YbK x-rays and the 82,2 keV gamma-rays from the gamma decay of the first excited state in¹⁷⁶Yb. With the data of the 88,36 keV gammarays following the beta decay of^176m Lu to the first excited state of¹⁷⁶Hf the electron capture/beta decay ratio of^176m Lu was found to be (0,95±0,16)·10^?4. The electron capture branching ratio to the ground state and to the first excited state of¹⁷⁶Yb was found to be 40/60±30%. By analyzing the 88,36keV gamma-rays and the HfKx-rays the halflife of^176m Lu was evaluated to be 3,66±0,04 h. The value for theK-conversion coefficient of the 88,36keV transition was determined from the x-ray/gamma-ray ratio to be 1,19±0,09.     

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.     

Study of159Yb decay

Theβ ⁺-decay of 1.4 min¹⁵⁹Yb was studied at the YAS-NAPP-2 facility installed on the proton beam of the JINR Dubna phasotron. The singles γ-ray spectra and prompt and delayedγ-γ coincidences were measured on the multidetector system. The decay scheme of¹⁵⁹Yb was proposed on the basis of theγ-γ coincidence data. The low lying states of¹⁵⁹Tm were preliminary identified within the framework of the rotational model.     

In-beam study of174Lu isomers

Levels in¹⁷⁴Lu have been investigated using the¹⁷⁶Yb(p,3n) reaction. Prompt and delayedγ-ray spectra have been observed with a 0.56-cm³ Ge(Li) detector by a multispectrum analysis method. The half-life and decay mode of two isomeric levels, one at 240.8keV (395±15ns) and the other at 365.1keV (145±3ns) have been firmly established. Hindrance factors are discussed. New delayed transitions in¹⁷⁵Lu are also noted.     

Theα- andβ-decay of187Pb

Sources of¹⁸⁷Pb were produced by the¹⁴²Nd(⁴⁸Ti, 3n)¹⁸⁷Pb reaction followed by online mass separation of the products. Measurements ofγ-γ andα-γ coincidences and half-lives were performed. Twoα-emitting states in¹⁸⁷Pb were found with half-lives of 15.2±0.3 s and 18.3±0.3 s, respectively. Theα-γ coincidences yielded excitation energy and possible spin values for a few levels in¹⁸³Hg. Gamma-transitions in¹⁸⁷Tl were identified and a level scheme for¹⁸⁷Tl is proposed on the basis of the coincidence relationships and the level systematics of the heavier odd-thallium isotopes.     

Bestimmung der Triplett-Potentialdaten für das K2-Stoßmolekül

Short lived Ru isotopes produced in thermal fission of²³⁵U have been chemically separated from the other fission products. Successiveγ-ray spectra were taken by means of Ge(Li) detectors. The observedγ-lines have been assigned to the various Ru isotopes (A=107 to 110) or to their daughter elements on the basis of their half-lives, intensity ratios and known level properties. Partial decay schemes are discussed and relative fission yields are given.¹¹¹Ru has been identified (T ₁₂: 1.5±0.3 s).     

Studies of γ-ray transitions in171Yb

The decay of¹⁷¹ Lu(t_1/2=8.2 day) to the levels of¹⁷¹Yb has been studied using large volume high resolution Ge(Li), x-ray Ge(Li) and NaI(Tl) detectors.γ-γ coincidence and directional correlation experiments have been performed. Spin-parity of 5/2^?, 7/2⁺, 5/2^?, 9/2⁺, 7/2^?, 7/2^?, 11/2⁺, 9/2^?, 9/2^? and 5/2^? have been assigned to the 75.87, 95.26, 122.37, 167.62, 208.00, 230.61, 259.02, 835.21, 948.37 and 1024.87 keV levels respectively. Several new coincidence relations have been observed in the present work. Two newγ-transitions at 141.45 and 821.30 keV observed and two levels at 766 and 944 keV been proposed. Multipolarity assignments have been made for most of theγ-transitions from theK-shell internal conversion coefficients obtained using the presentγ-ray intensities and the published conversion electron intensities. A revised level scheme for¹⁷¹Yb has been proposed and compared with published data. Radioactivity¹⁷¹Lu; measuredT _1/2,E _γ ,I _γ ,γγ coin,γγ (θ), I.C.C.,¹⁷¹Yb deduced levels,J, γ-mixing,π. Enriched targets, Ge(Li) detectors.     

A new beta decaying isomer of131Sn; partial level scheme of131Sb

Gamma spectrum and half life of¹³¹Sn decay have been measured using the unslowed fission fragment separator Lohengrin at the high flux reactor of the Institute Laue-Langevin, Grenoble. Two beta-decaying isomers are evidenced, with half-lives of 39±2 s and 50±2 s. Additional confirmation of this isomerism is given by fission fragment-γ delayed coincidence, leading to a partial level scheme of¹³¹Sb including an isomeric level of 50±8 μs life-time at 1676.6 keV.     

The decay of 31 sec98Zr, 2.9 sec98Nb and 51 min98Nb

TheΒ- andγ-radiations of⁹⁸Zr and^{98m, g} Nb have been investigated employing scintillation and semiconductor spectrometers and coincidence techniques. Sources of⁹⁸Nb were produced by the⁹⁸Mo(n, p)⁹⁸Nb reaction, sources of⁹⁸Zr by fission of²³⁵U with thermal neutrons applying chemical separations. For⁹⁸Zr, a half-life of 30.7±0.4 sec and aQ _β-value of 2.3±0.2 MeV were obtained, for the⁹⁸Nb isomers, half-lives of 2.86±0.06 sec and 51.3±0.4 min, andQ _β-values of 4.8±0.2 MeV and 4.5±0.2 MeV, respectively. Noγ-rays were observed in the decay of⁹⁸Zr. The decay of 2.9 sec⁹⁸Nb was found to involve 11γ-ray transitions. In the decay of 51 min⁹⁸Nb, 54γ-transitions were detected. Spin and parity of 1⁺ and 4^? were deduced for the isomeric states of⁹⁸Nb.     

A note on the structure of the 1518 keV isomeric state in174Yb

Studies of the decay of¹⁷⁴Tm and^174m Lu show that, in both cases, a level at 1517.6±0.8 keV in¹⁷⁴Yb is populated, which decays to the 4⁺, 6⁺ and 8⁺ members of the g.s. rotational band.     

Search for an isomer in94Rb

Measurements of theβ-ray half-life,γ-ray and X-ray spectra andγ-ray half-lives have been done with a plastic scintillation detector, a high resolution Ge(HP) detector and a 142 cm³ Ge(Li) detector to search for an isomeric state in⁹⁴Rb. Mass-separated activities of⁹⁴Rb were obtained from the He-jet type on-line mass-separator at the Kyoto University reactor. No isomeric transition was found in theγ-ray and X-ray measurements with the upper limits of 3×10^?4 and 8×10^?5, respectively, as compared with the 836.9 keV transition. Half-lives obtained from theγ-ray decay measurements are discussed in the light of classification given byQ _β -value measurements.     

New neutron-rich 179Yb and 181,182Lu isotopes produced in reactions of 9 MeV/u 136Xe ions on tantalum and tungsten targets

The new neutron-rich isotopes ¹⁷⁹Yb and ^181,182Lu were produced in multinucleon transfer reactions by irradiating ^natW/Ta targets with 9 MeV/u ¹³⁶Xe ions, and identified by mass separation and decay spectroscopy. The measured half-lives of ¹⁷⁹Yb, ¹⁸¹Lu and ¹⁸²Lu are 8.1±0.8, 3.5±0.3 and 2.0±0.2 min, respectively. The properties of the excited states of ^181,182Hf are discussed. The possibility of studying neutron-rich nuclei outside the classical fission-product regions is demonstrated.     

Decay of90m,g Rb

The decay of mass separated⁹⁰Rb has been studied usingβ,γ and conversion electron spectrometers in single and coincidence modes. The half-lives of the ground state and the isomeric level have been confirmed to be 162± 3 and 258±4 s, respectively. Theγ-rays from the decays of ground state and metastable state have been identified by measuring the decay of individual photopeaks using Ge(Li) detectors. The multipolarity of the 106.6 keV isomeric transition has been determined to beM3. Separate decay schemes of the ground and metastable states are presented. The levels of⁹⁰Sr are discussed in terms of the available experimental and theoretical information. Radioactivity.^90m,gRb [from²³⁸U(p, f)]; measuredT _1/2,E _γ,I _γ,γ—γ coin,I _ce,cc,E _β deduced logft,⁹⁰Sr levels, mass separated⁹⁰Rb.     

TheEC-decay of170Tm

The spectrum ofK X-rays andγ-rays following the decay of¹⁷⁰Tm has been reinvestigated using a high resolution Si(Li) detector. The intensities of theEC-branches from the ground state of¹⁷⁰Tm to the ground state as well as to the first excited level in¹⁷⁰Er have been measured. The total intensity of theEC-decay is (0.25 ± 0.05)% of all¹⁷⁰Tm disintegrations with (0.18 ± 0.05)% leading to the ground state and (0.07±0.02)% leading to the first excited level of¹⁷⁰Er. The energy of the de-excitingγ-ray has been determined to (78.7±0.5) keV. Its intensity is (0.28 ± 0.06)% of that of the 84.3 keVγ-ray in¹⁷⁰Yb.     

Specific heat of the superfluid neutron matter in neutron star crusts

By means of X-γ andγ-γ coincidence measurements of the³⁵Cl+⁵⁸Ni reaction products, 38γ lines have been identified to be in coincidence with KX(Tc)-rays and assigned to the decay of⁹⁰Ru. Its half-life of 11±3 s has been deduced from the 154.6 keVγ-decay. The result supports our previous identification of⁹⁰Ru produced in the same reactions.     

The β decay of tellurium 135 and 137

Tellerium 135 and 137 nuclei were produced in thermal neutron fission of²³⁵U separated by on-line isotope separator and deposited on a movable tape. Gamma ray singles,γ-γ, β-γ coincidences and time sequencedγ spectra were collected using Ge(Li) detectors and scintillator (NE 102 A) telescope. The half-lives and mass excesses of¹³⁵Te and¹³⁷Te were measured and level schemes of¹³⁵I and¹³⁵I have been established. The level scheme of¹³⁵I has been compared to different shell model calculations.     

Half-life measurements and gamma spectroscopy in the decay184Re m →184W

The half-lives of the intrinsic states at 1,285.8 and 1,502.2 keV in¹⁸⁴W have been measured in the decay of¹⁸⁴Re ^m to be 8.33±0.18Μs and 2.35±0.10 ns, respectively. These half-lives determine absolute gamma-ray transition probabilities of eight transitions and yield upper limits for three transitions. The decay scheme of¹⁸⁴Re ^m →¹⁸⁴W is improved through measurements of delayed gamma-ray spectra with a Ge(Li) detector. Spin and Nilsson model interpretations are discussed.     

g-factor of the 4 1 + rotational state of160Dy

By use of Ge-detectors of the OSIRIS-collaboration [1] in connection with the 12 detector IPAC apparatus of our laboratory [2] a precise measurement of theg-factor of the 4 ₁ ⁺ rotational state of¹⁶⁰Dy was performed. The directional correlations of the threeγ-γ cascades, 1003-197 keV, 1103-197 keV and 1115-197 keV, which are weakly populated in the decay of 72.3 d¹⁶⁰Tb were observed simultaneously. The integral rotations in the static hyperfine field of DyTb at 4.2 K were measured. Theg-factorg(4 ₁ ⁺ )=+0.350(20) was derived. By comparison with the magnetic splitting of the 2 ₁ ⁺ rotational state observed in the same environment by a Mössbauer experiment [3] the ratio of the twog-factors was derived as g(4 ₁ ⁺ )/g(2 ₁ ⁺ )=+ 0.91(5). For the high energy lines we derived from the measured directional correlations the E1/M2 mixing parameters: δ(1003 keV)=+0.005(4); δ(1103 keV)=?0.020(22), and δ(1115 keV)=+0.010(4)     

Theβ + decay of the new isotope86Mo and the first observation of86m Nb

Theβ ⁺ decay of⁸⁶Mo has been firstly investigated by means ofβγ spectroscopy. The⁸⁶Mo nuclei were produced by fusion-evaporation reactions of⁵⁴ Fe (³⁵Cl, 1 p2n) and⁵⁸Ni (³²S,2p 2n) at beam energies of 103 and 120 MeV, respectively. Threeγ rays of 47.3, 49.8 and 187.0 keV were unambiguously identified to follow theβ ⁺ decay of⁸⁶Mo by results ofXγ andβγ coincidence and cross-bombardment. A half life and a maximumβ ⁺-ray energy of⁸⁶Mo were determined to be 19.6±1.1 s and 3.9±0.4 MeV, respectively. A decay scheme of⁸⁶Mo is proposed in this article. Furthermore, a decay of⁸⁶Nb has been studied using the same combinations of projectiles and targets, and a newβ-decaying isomer^86m Nb was observed with a half life of 56.3±8.3 s.