Alpha-decaying low-spin levels in155Lu and157Lu

Using an on-line mass separator, the -particle decays of¹⁵⁵Lu and¹⁵⁷Lu were investigated. A new -emitting level in¹⁵⁷Lu was identified [T_1/2=5.7(5) s,E =4924(20) keV]. In addition, a half-life of 140(20) ms was measured for the recently discovered second, low-lying, -decaying level [E =5579 (5)keV] in¹⁵⁵Lu.We wish to thank L.F. Archambault, R.B. Firestone, A.A. Shihab-Eldin, and A.A. Wydler for their contributions to this experimental program. We also express thanks to the staff of the SuperHILAC for providing smooth operation of the accelerator.     

A 35 μs isomer in the exoticN=83 Nucleus154Lu

The⁷⁰Ge(α,nγ)⁷³Se reaction was used to populate medium spin states of the⁷³Se nucleus. Spins and parities up to about I^π=(21/2⁺)? were determined by gamma angular distribution, gamma linear polarization and excitation function measurements.     

New shape isomer in the self-conjugate nucleus 72Kr

A new isomeric 0(+) state was identified as the first excited state in the self-conjugate (N=Z) nucleus 72Kr. By combining for the first time conversion-electron and gamma-ray spectroscopy with the production of metastable states in high-energy fragmentation, the electric-monopole decay of the new isomer to the ground state was established. The new 0(+) state is understood as the band head of the known prolate rotational structure, which strongly supports the interpretation that 72Kr is one of the rare nuclei having an oblate-deformed ground state. This observation gives in fact the first evidence for a shape isomer in a N=Z nucleus.     

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.     

Magnetic moment of theI π=23/2− isomer in177Lu and additivity in the deformed region

^177g Lu and^177m Lu with half lives of 6.8d and 161d, respectively, were implanted into iron foils and oriented at low temperatures. From the temperature dependence of the anisotropies of severalγ-rays the magnetic moment of theI ^π=23/2^? three quasiparticle isomeric state^177m Lu was determined asμ=3.3±0.3 nm. It is shown that the additivity relation for magnetic moments is well fulfilled for four high spin multiparticle states in this mass region. Using the known magnetic moment of the ground state a value of ¦H¦=377±15 kG was derived for the internal field of Lu in Fe for our sample.     

New investigation of the decay of the high-spin isomer in 151Er

The decay of the T _1/2 = 420 ns isomer in ¹⁵¹Er has been reinvestigated. The multipolarities of the decaying transitions have been established by measuring the electron conversion coefficients. An I ^π = 67/2⁻ assignment is proposed for this isomer with a π[h ₁₁^2/4 d ₃^2/1 d ₅^2/−1]⊗ν[f _7/2 h _9/2 h ₁₁^2/−1] configuration.     

Oblate high spin isomer

Energies of high spin states are calculated with the use of an oblate deformed oscillator potential with the purpose of finding possible yrast traps or isomers. Pairing forces are included and different methods of solving the pairing Hamiltonian (including the exact solution) are compared. The stability of the oblate regime against gamma vibrations is investigated with use of the random phase approximation. Pairing forces are included also here.     

原子核同核异能态诱发辐射研究进展

介绍了同核异能态的特点和诱发同核异能态的几种机制,如直接光激发、电子跃迁诱导核激发(NEET)和电子俘获诱导核激发(NEEC)。同核异能态的诱发辐射研究目前在国际上竞争激烈,尤其是对最近提出的NEEC的研究。同时探讨了在我国开展这些研究的可能性。     

High-spin isomer in 93Mo

The high-spin states of ⁹³Mo have been studied by a ⁸²Se( ¹⁶O, 5n) ⁹³Mo reaction at a beam energy of 100 MeV using techniques of in-beam -ray spectroscopy. Measurements of -t, --t coincidences, -ray angular distributions and -ray linear polarizations were performed. The high-spin isomer was found as a (39/2^-) state at about 9.7 MeV. The near-yrast states in ⁹³Mo were interpreted using the weak-coupling picture of a d_5/2 neutron to a neutron magic core nucleus ⁹²Mo.     

Electron densities and isomer shift

Some of the problems concerning the absolute determination of electron density changes from Mössbauer isomer shift data are discussed. Three promissing experimental methods based on conversion electron spectroscopy, lifetime measurements, and muonic isomer shift measurements are presented.     

原子核同核异能态诱发辐射研究进展

介绍了同核异能态的特点和诱发同核异能态的几种机制,如直接光激发、电子跃迁诱导核激发(NEET)和电子俘获诱导核激发(NEEC)。同核异能态的诱发辐射研究目前在国际上竞争激烈,尤其是对最近提出的NEEC的研究。同时探讨了在我国开展这些研究的可能性。     

The fissioning isomer 237Npm

A spontaneously fissioning isomer of ²³⁷Np with a half-life of 40±12 ns has been discovered. Threshold measurements indicate that the isomer excitation energy is 2.7 ± 0.3 MeV. It is concluded that spontaneous fission is not the principal decay mode for this shape isomer.     

New aspects of micromachining and microlithography using 157-nm excimer laser radiation

The use of F₂ excimer laser sources, emitting at 157 nm, constitutes a new promising tool for scientific, industrial and lithography applications. The 157-nm laser emission enables high-resolution processes and the high photon energy offers the unique possiblity of photoionizing molecules in a single step. Therefore a lower fragmentation or thermal loading takes place. The 157-nm radiation will enable fundamental research and development for deep UV (DUV) high-resolution optical microlithography in the manufacturing of integrated circuits. This is the next step from the technology of ArF lasers at 193 nm. Furthermore, benefits are expected for key technologies requiring high-resolution processing and the micromachining of tough materials like Teflon or fused silica for micro-optics fabrication. Such applications require F₂ excimer laser sources with high performance, reliability and efficiency. The world of nanotechnology is just beginning to reveal its potential.     

A new isomer in205Po

A new isomer withT _1/2=58±2 ms has been observed in²⁰⁵Po. We propose the assignmentsI ^π = 19/2^? and an excitation energyE _x =1461 keV.     

High spin isomer in151Sm

An investigation of the high spin isomer in¹⁵¹Sm was performed via the¹⁵⁰Nd(α, 3nγ) reaction at a projectile energy of 35 MeV. A newγ-transition, 693.6 keV was identified having an exponential delayed component. The transition feeds the 1912 keV state of the negative parity band built on theh _11/2 state. This transition was also observed in coincidence withγ-rays belonging to¹⁵¹Sm in theγ-γ coincidence experiment atE _α =37 MeV. A new isomeric state having energyE _x =2605.8 keV and half lifeT _1/2=23.1±3.5 ns is proposed.     

Nuclear orientation of171Lu and173Lu

The decays of¹⁷¹Lu and¹⁷³Lu have been studied by means of nuclear orientation. External perturbations of two¹⁷¹Yb levels have been observed. Unambiguous spin assignments have been made for several levels in¹⁷¹Yb and mixing ratios of the transitions in¹⁷¹Yb and¹⁷³Yb have been deduced. The properties of the¹⁷¹Yb and¹⁷³Yb rotational bands have been studied using the quasiparticle-phonon model including a Coriolis interaction.     

A new isomer in 125La

Levels in ¹²⁵La have been studied via #⁺/EC decay of on-line mass-separated ¹²⁵Ce using the HIGISOL technique. A new (390 - 40) ms isomer is definitely attributed to ¹²⁵La by conversion electron measurements of the 107 keV E3 isomeric transition.