A very exotic process of β-delayed fission of 180Tl is studied in detail by using resonant laser ionization with subsequent mass separation at ISOLDE (CERN). In contrast to common expectations, the ...fission-fragment mass distribution of the post-β-decay daughter nucleus 180Hg (N/Z=1.25) is asymmetric. This asymmetry is more surprising since a mass-symmetric split of this extremely neutron-deficient nucleus would lead to two 90Zr fragments, with magic N=50 and semimagic Z=40. This is a new type of asymmetric fission, not caused by large shell effects related to fragment magic proton and neutron numbers, as observed in the actinide region. The newly measured branching ratio for β-delayed fission of 180Tl is 3.6(7) × 10(-3)%, approximately 2 orders of magnitude larger than in an earlier study.
In this paper we describe the stratospheric and mesospheric ozone (version V5r_O3_m22) distributions retrieved from MIPAS observations in the three middle atmosphere modes (MA, NLC, and UA) taken ...with an unapodized spectral resolution of 0.0625 cm−1 from 2005 until April 2012. O3 is retrieved from microwindows in the 14.8 and 10 µm spectral regions and requires non-local thermodynamic equilibrium (non-LTE) modelling of the O3 v1 and v3 vibrational levels. Ozone is reliably retrieved from 20 km in the MA mode (40 km for UA and NLC) up to ∼ 105 km during dark conditions and up to ∼ 95 km during illuminated conditions. Daytime MIPAS O3 has an average vertical resolution of 3–4 km below 70 km, 6–8 km at 70–80 km, 8–10 km at 80–90, and 5–7 km at the secondary maximum (90–100 km). For nighttime conditions, the vertical resolution is similar below 70 km and better in the upper mesosphere and lower thermosphere: 4–6 km at 70–100 km, 4–5 km at the secondary maximum, and 6–8 km at 100–105 km. The noise error for daytime conditions is typically smaller than 2 % below 50 km, 2–10 % between 50 and 70 km, 10–20 % at 70–90 km, and ∼ 30 % above 95 km. For nighttime, the noise errors are very similar below around 70 km but significantly smaller above, being 10–20 % at 75–95 km, 20–30 % at 95–100 km, and larger than 30 % above 100 km. The additional major O3 errors are the spectroscopic data uncertainties below 50 km (10–12 %) and the non-LTE and temperature errors above 70 km. The validation performed suggests that the spectroscopic errors below 50 km, mainly caused by the O3 air-broadened half-widths of the v2 band, are overestimated. The non-LTE error (including the uncertainty of atomic oxygen in nighttime) is relevant only above ∼ 85 km with values of 15–20 %. The temperature error varies from ∼ 3 % up to 80 km to 15–20 % near 100 km. Between 50 and 70 km, the pointing and spectroscopic errors are the dominant uncertainties. The validation performed in comparisons with SABER, GOMOS, MLS, SMILES, and ACE-FTS shows that MIPAS O3 has an accuracy better than 5 % at and below 50 km, with a positive bias of a few percent. In the 50–75 km region, MIPAS O3 has a positive bias of ≈ 10 %, which is possibly caused in part by O3 spectroscopic errors in the 10 µm region. Between 75 and 90 km, MIPAS nighttime O3 is in agreement with other instruments by 10 %, but for daytime the agreement is slightly larger, ∼ 10–20 %. Above 90 km, MIPAS daytime O3 is in agreement with other instruments by 10 %. At night, however, it shows a positive bias increasing from 10 % at 90 km to 20 % at 95–100 km, the latter of which is attributed to the large atomic oxygen abundance used. We also present MIPAS O3 distributions as function of altitude, latitude, and time, showing the major O3 features in the middle and upper mesosphere. In addition to the rapid diurnal variation due to photochemistry, the data also show apparent signatures of the diurnal migrating tide during both day- and nighttime, as well as the effects of the semi-annual oscillation above ∼ 70 km in the tropics and mid-latitudes. The tropical daytime O3 at 90 km shows a solar signature in phase with the solar cycle.
The new isotope 179Pb has been produced in the complete fusion reaction 40Ca + 144Sm → 179Pb+5n at the velocity filter SHIP (GSI). Its α-decay energy of 7350(20) keV and half-life value of 3.5+1.4− ...0.8 ms were deduced based on the recoil–α–α correlation technique. A spin parity of Iπ = (9/2−) was tentatively assigned to the ground state of 179Pb; thus, it is based on the 1h9/2 orbital. Improved measurements of the α-decay properties of 179Tlm and 175Aum are also presented.
Fission fragment mass distributions were measured in heavy-ion induced fissions using super(238)U target nucleus. The measured mass distributions changed drastically with incident energy. The results ...are explained by a change of the ratio between fusion and qasifission with nuclear orientation. A calculation based on a fluctuation dissipation model reproduced the mass distributions and their incident energy dependence. Fusion probability was determined in the analysis, and the values were consistent with those determined from the evaporation residue cross sections.
The synthesis of element 116 in fusion-evaporation reactions of a
48
Ca beam with radioactive
248
Cm targets was studied at the velocity filter SHIP of GSI in Darmstadt. At excitation energies of the ...compound nuclei of 40.9MeV, four decay chains were measured, which were assigned to the isotope
292
116, and one chain, which was assigned to
293
116. Measured cross-sections of (3.4
−1.6
+2.7
) pb and (0.9
−0.7
+2.1
), respectively, and decay data of the chains agree with data measured previously at the Flerov Laboratory of Nuclear Reactions in Dubna. As a new result, one
α
-decay chain was measured, which terminates after four
α
decays by spontaneous fission. The
α
energies of the second-to-fourth decay are considerably higher than those measured for the
α
decays of
289
114,
285
Cn, and
281
Ds and the spontaneous fission half-life is significantly longer than that of
277
Hs measured in previous experiments. A possible assignment is discussed in the frame of excited quasiparticle states of nuclei populated in the decay chain from
293
116. Also other possible assignments were considered and are discussed. At an excitation energy of 45.0MeV no events were observed resulting in a one-event cross-section limit of 1.6 pb. The technical aspects related with the use of radioactive target material at SHIP are described in detail. The experience gained in this experiment will serve as a basis for future experiments aiming to study still heavier elements at the velocity filter SHIP.
The new isotope 208Th Heredia, J. A.; Andreyev, A. N.; Antalic, S. ...
The European physical journal. A, Hadrons and nuclei,
12/2010, Letnik:
46, Številka:
3
Journal Article
Recenzirano
.
The new neutron-deficient isotope
208
Th was produced in the complete-fusion reaction
64
Ni +
147
Sm
208
Th + 3n . Evaporation residues were separated in-flight by the velocity filter SHIP and ...subsequently identified on the basis of energy-, position- and time-correlated
-decay chains. The measured
-decay energy and half-life value of
208
Th are 8044(30)keV and 1.7
+1.7
-0.6
ms, respectively. Improved data on the
-decay of
209
Th ,
210
Th ,
212
Th and
208
Ra were obtained using complete-fusion reactions of
64
Ni with
147
Sm ,
150
Sm , and
152
Sm targets.
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