0000000000328425
AUTHOR
J. Honkanen
Beta-delayed particle emission of 36K
Abstract 36 Ar targets of 19 μg cm 2 thickness were made by a sandwich technique in which a 70 nm layer of Al was evaporated onto the implanted Al surface between five successive implantations of 36 Ar ions. The sources of 36 K were prepared by depositing the recoil atoms from the 36 Ar(p, n) 36 K reaction by means of a helium jet onto a fast transport tape. The measured delayed particle spectra revealed 11 proton groups (0.5 MeV E p E α 36 K. Total proton and α-particle branching ratios were measured to be 4.8 × 10 −4 and 3 × 10 −5 , respectively. Partial level widths and reduced proton and α-particle transition widths were determined for several individual levels with the aid of additiona…
Discovery of New Fission Product Activities in the A=110–118 Mass Region
Neutron rich nuclei around the mass A=100 have recently attracted both theoretical and experimental interest since they are expected to form a new region of strong deformation. In contrary, very little experimental information is available in the adjacent transitional region A= 110–118. Due to expected isomerism in this region both low and high spin states can be studied via beta decay in many nuclei. The studies of these nuclides have many experimental difficulties. They are only weakly produced in thermal neutron induced fission and because all the elements in this mass region (Tc, Ru, Rh, Pd) have very high melting points they have not been available as beams of on-line isotope separator…
The $\beta$-delayed one- and two-proton emission of $^{27}$S
In an experiment performed at the GANIL LISE3 facility, radioactive 27S isotopes have been produced by projectile fragmentation of a 95 AMeV 36Ar primary beam. After selection by means of the LISE3 separator, the isotope of interest was implanted in a silicon-detector telescope where its half-life ( T 1/2 = 15.5(15) ms) and its main decay branches were measured.
Selected Aspects in the Structure of Beta-Delayed Particle Spectra
Some weak beta-delayed particle emitters in the Tz = -3/2, -1, -1/2, +1/2 and +5/2 series are reviewed. Selected features of the delayed particle emission are discussed in terms of experimental delayed particle data and (p, γ), (p, p') and (p, n) reaction data. Experimental beta transition strengths are compared with the existing complete shell-model calculations for the sd-shell nuclei. The effect of the Gamow-Teller giant resonance on the structure of the delayed particle spectra is considered. The correlation between the widths of two decay channels, protons and alpha particles, and the preceeding beta decay is studied in the case of the 40Sc decay.
Decay of24Al and24Almto γ-Ray and α-Particle Emitting States in24Mg
The level structure of 24Mg and decay properties of 129 ms 24Alm and 2.07 s 24Al have been investigated by means of γ-ray and particle spectroscopy. The energy and intensity of the isomeric transition were measured to be 425.8 ± 0.1 keV and (82.5 ± 3.0)%, respectively. The isomer was observed to decay via a super-allowed transition with a log ft value of 3.51 ± 0.04 to its 1+, 9965.2 ± 1.5 keV analog state in 24Mg. In addition, decay to seven particle-emitting levels and four levels depopulated by γ-ray emission were observed. In the decay of 2.07 s 24Al a new delayed α-particle group with an energy 3.04 MeV and three new γ-transitions were observed. More accurate values than those reported…
Separation of fission products by the ion guide fed isotope separator, IGISOL
Abstract The performance of the ion guide method in the on-line mass separation of fission products has been investigated. Activity was produced by bombarding nat. U targets with a beam of 20 MeV protons. All the mass chains from A = 95 through A = 120 have been scanned using conventional methods of nuclear spectroscopy. No chemical selectivity in the separation was observed; isotopes of highly nonvolatile elements from yttrium to palladium were produced with efficiencies equal to those for the more volatile ones. The boundary of known neutron-rich nuclides was reached throughout the mass region from A = 106 to A = 118. During the course of this preliminary study the new isotope 116 Rh was …
Submillisecond On-Line Mass Separation of Nonvolatile Radioactive Elements: An Application of Charge Exchange and Thermalization Processes of Primary Recoil Ions in Helium
Transportation of thermalized primary recoil ions from nuclear reactions by helium flow has been investigated as a means of injecting short-lived radioactive nuclides into an on-line isotope separator. Several short-lived radioactive isotopes of highly nonvolatile elements such as B, Sc, Nb, and W have been separated. The efficiency for heavy nuclides with half-lives above 1 ms is between 1 and 10%. The shortest-lived activity identified in an on-line separation is the 182-\ensuremath{\mu}s isomeric state in $^{207}\mathrm{Bi}$.
Half-life and configuration of the 1/2+ intruder state in203Bi
The decay properties of theJπ=1/2+,Eexc=1,098 keV state in203Bi were studied. The state was populated via the204Pb(p, 2n) reaction and the activity was studied with the ion guide isotope separator on-line system IGISOL. The half-life of the 1/2+ state was measured to beT1/2=303 ±5 ms. From this value the partial half-lives of the three depopulating branches 1/2+ →7/2− (E3), 1/2+→5/2− (E3 +M2) and 1/2+→9/2 g.s. − (M4) were deduced. Since all the transitions are configuration forbidden in first order, a detailed study of second-order shell-model configuration mixing could be performed.
Spectroscopic studies of neutron-deficient light nuclei: decay properties of 21Mg, 25Si and 26P
Neutron‐deficient nuclei with Tz equals to −3/2 and −2 have been produced at the GANIL/LISE3 facility in fragmentation reactions of a 95 MeV/u 36Ar primary beam in a 12C target. For the first time, β‐delayed proton and β‐γ emission has been simultaneously observed in the decay of 21Mg, 25Si and 26P. The decay scheme of the latter is proposed and the Gamow‐Teller strength distribution in its β decay is compared to shell‐model calculations based on the USD interaction. The B(GT) values derived from the absolute measurement of the β‐branching ratios are in agreement with the quenching factor of about 60% obtained for allowed Gamow‐Teller transitions in this mass region. A precise half‐life of …
Gamow-Teller decay of118Pd and of neighbouring even isotopes of palladium
Neutron-rich isotopes of palladium were produced via the fission of238U by 20 MeV protons. These isotopes were selected using the ion guide-fed on-line mass-separator facility IGISOL at Jyvaskyla. Their decays were studied byβ-ray,γ-ray and conversion-electron spectroscopy. For114Pd and116Pd, the decay schemes established previously were confirmed; additionally multipolarities were determined for a few transitions. In the case of118Pd, only an approximate half-life was known from a previous radiochemical experiment. In the present study, 15 gamma transitions were observed, most of which were placed in a decay scheme. The half-life and the decay energy were found to beT1/2=1.9±0.1 s andQβ=4.…
A study of a helium-jet ion guide for an on-line isotope separator
Abstract A new method based on helium-jet techniques permits primary recoil ions, produced in radioactive decay or in nuclear reactions to be run directly through a mass separator. Results obtained with a 227 Ac source promise qualities complementary with those obtained with conventional ion sources and indicate an overall efficiency of the order of 10%. Preliminary results with 20 Na recoils from the 20 Ne(p,n)-reaction indicate that most of the ionic species transported out from the target chamber are negatively charged.
Beta decay of 40Sc to proton and alpha-particle unbound states in 40Ca
Delayed charged particle emission associated with the precursor nuclide 40Sc was studied by use of the He-jet technique. Altogether 40 proton groups (1.0 MeV < Ep < 3.7 MeV) and 21 α-particle groups (2.0 MeV < Eα < 4.6 MeV) were observed. Total proton and α-particle branching ratios were measured to be (4.4±0.7) × 10−3 and (0.17±0.05) × 10−3, respectively. Association of the delayed particle emitting levels with the levels observed in resonance reaction studies is discussed. The fact that the most prominent α-particle groups do not have a counterpart in resonance reaction data suggests collectivity or a cluster configuration for the emitting levels. Log ft values (upper limits) for β+ trans…