New insights from studies of spontaneous fission with large detector arrays

Survey of short-lived fission products obtained using the isotope-separator-on-line facility at Studsvik

Rotational bands in the mass 100 region

Axial and reflection asymmetry of the nuclear ground state

Nuclear Data Sheets for A = 106

Einige mehr orientierende Versuche mit anderen Nukliden sollten schließlich noch zeigen, daß das hier eingehend untersuchte System kein Sonderfall ist. Dazu wurden wägbare Mengen an radioaktiv markiertem Kobalt, Zink, Thallium oder Blei gemeinsam mit Wismut aus komplexalkalischem, borsäurehaltigem Medium abgeschieden; die Wismutschicht war 1,0 mg/cm, die der Fremdkomponente 0,2 mg/cm dick. Nach der Abscheidung wurde die Schicht bei einem Potential von 0 , 0 5 bis 0 , 1 5 V in 0,5 η Salzsäure (Zn, Tl) oder 0,5 η Salpetersäure (Co, Pb) von 70 °C gebracht. Innerhalb von 2-3 min waren 97 + 4% des Zinks, 98 + 2 % des Thalliums und 90% des Bleis abgelöst, während die Ablösung des Kobalts langsam verlief und nach 20 min erst 75% umfaßte.

Identification of short-lived isotopes of zirconium, niobium, molybdenum, and technetium in fission by rapid solvent extraction techniques

The decay of neutron-rich niobium isotopes in the mass region $A\ensuremath{\simeq}100$ has been investigated by $\ensuremath{\gamma}$-ray singles and $\ensuremath{\gamma}$-$\ensuremath{\gamma}$ coincidence measurements. The isotopes were produced by thermal-neutron induced fission of $^{235}\mathrm{U}$, $^{239}\mathrm{Pu}$, and $^{249}\mathrm{Cf}$, and niobium was separated from fission-product mixtures with an automated chemical procedure. Isomerism was found in the even-mass niobium isotopes with the following half-lives: 1.5 and 3.1 sec for $^{100}\mathrm{Nb}$, 1.3 and 4.3 sec for $^{102}\mathrm{Nb}$, and 0.8 and 4.8 sec for $^{104}\mathrm{Nb}$. Half-lives and $\ensuremath{\gamma}$ rays were assigned to the 15.0-sec $^{99}\mathrm{Nb}$, 7.1-sec $^{101}\mathrm{Nb}$, 1.5-sec $^{103}\mathrm{Nb}$, and \ensuremath{\sim}1-sec $^{106}\mathrm{Nb}$. Revised half-life values are given for the 7.1-sec $^{100}\mathrm{Zr}$ and 2.9-sec $^{102}\mathrm{Zr}$. RADIOACTIVITY $^{99,100,101,102,103,104,106}\mathrm{Nb}$, $^{100,102}\mathrm{Zr}$; measured ${T}_{\frac{1}{2}}$, ${E}_{\ensuremath{\gamma}}$, $\ensuremath{\gamma}$-$\ensuremath{\gamma}$-coin. $^{100,102,104}\mathrm{Mo}$ deduced levels. Fission $^{235}\mathrm{U}$, $^{239}\mathrm{Pu}$, $^{249}\mathrm{Cf}({n}_{\mathrm{th}},f)$; automated chemical separation procedure, Ge(Li) detectors.

Decay properties of neutron-rich niobium isotopes

The nucleus103Nb62 has been studied through the s− decay of the fission product103Zr at LOHENGRIN and JOSEF. The energies of the lowlying levels and the γ transitions indicate rotational bands based on the Nilsson proton configurations [422 5/2+] [303 5/2−] and [301 3/2−] at 0, 164 and 248 keV, respectively. The measured half-lives of (4.7±0.5) ns and (2.0±0.6) ns of the levels at 164 and 248 keV are consistent with the Nilsson-model estimates including pairing.

Evidence for rotational bands in103Nb

A search with radiochemical methods for long-lived superheavy elements in 238U targets bombarded with intense beams of136Xe ions produced negative results. A formation cross section of ≤1×10−35 cm2 is deduced at 95% confidence level for nuclides with half-lives between 1 and 200 d.

H. Ahrens

Papers

Identification of short-lived isotopes of zirconium, niobium, molybdenum, and technetium in fission by rapid solvent extraction techniques

Decay properties of neutron-rich niobium isotopes

Evidence for rotational bands in103Nb

Search for long-lived superheavy elements in the reaction of136Xe with238U

Identification of 109 Tc and 110 Tc in fission of 249 Cf