Search results for "DECAY"
showing 10 items of 2087 documents
Experimental study of 1/2(+) isomers in At-199,At-201
2014
Using fusion-evaporation reactions, a gas-filled recoil separator, and recoil-electron and recoil-electron-alpha tagging techniques, a new isomeric 1/2(+) state [T-1/2 = 45(3) ms] in At-201 is identified, and an earlier reported corresponding state [T-1/2 = 273(9) ms] in At-199 is confirmed. The 1/2(+) state is suggested to originate from an intruder pi(s(1/2))(-1) configuration. In addition, nuclear structure of states below and above this 1/2(+) state are studied in both nuclei. The isomer decays through a cascade of an E3 transition followed by a mixed M1/E2 transition to the 9/2(-) ground state, and it is interpreted to be fed from nearly spherical 3/2(+) and 5/2(+) states originating f…
Nuclear moments of indium isotopes reveal abrupt change at magic number 82
2022
In spite of the high-density and strongly correlated nature of the atomic nucleus, experimental and theoretical evidence suggests that around particular 'magic' numbers of nucleons, nuclear properties are governed by a single unpaired nucleon1,2. A microscopic understanding of the extent of this behaviour and its evolution in neutron-rich nuclei remains an open question in nuclear physics3-5. The indium isotopes are considered a textbook example of this phenomenon6, in which the constancy of their electromagnetic properties indicated that a single unpaired proton hole can provide the identity of a complex many-nucleon system6,7. Here we present precision laser spectroscopy measurements perf…
Discovery of the new isotopes ²⁴⁰Es and ²³⁶Bk and in-beam spectroscopic studies of ²⁴⁴Cf
2017
The hitherto unknown neutron-deficient nuclei 240Es and 236Bk were synthesised using the fusion-evaporation reaction 209Bi(34S,3n)240Es. The ritu gas-filled recoil separator and the great spectrometer were used in this decay spectroscopic study. The measured electron-capture delayed fission (ECDF) branches in both of the new isotopes complement the experimental data available in the heavier odd-odd Es and Bk isotopes. Furthermore, the ECDF branches show a continuation in the exponential increase of the ECDF probabilities as a function of QEC − Bsf when approaching the proton dripline. In addition, an in-beam γ-ray spectroscopic study of the neutron-deficient isotope 244Cf was made using the fus…
Decay spectroscopy of the very neutron-deficient lead and thallium isotopes 178,179Pb and ¹⁷⁹Tl
2018
This thesis reports on the production of the very neutron-deficient isotopes 178,179Pb and 179Tl, using heavy-ion fusion-evaporation reactions. The gas-filled separator RITU and the GREAT spectrometer at its focal plane position were used for the decay spectroscopy study. The α decay of 178Pb and its α-decay chain were studied through α-α correlations. The α-particle energy and half-life were measured for 178Pb as, Eα= 7610(30) keV and t1/2 = 0.21−+0.21 0.08 ms, respectively. The half-life is consistent with recent theoretical calculations using the Coulomb and Proximity Potential Model (CPPM). The hindrance factor for 178Pb was deduced and corresponds to an unhindered Δl = 0 transition. Th…
Excited levels in the multishaped 117Pd nucleus studied via β decay of 117Rh
2018
Monoisotopic samples of exotic, neutron-rich 117Rh nuclei, produced in the proton-induced fission of 238U and separated using the IGISOL mass separator coupled to the JYFLTRAP Penning trap, were used to perform β and γ coincidence spectroscopy of 117Pd. The spin parity of the ground state of 117Pd was determined to be 1/2+ and the 19.1 ms isomer at 203.2 keV was assigned a spin-parity 7/2−. The 117Rh β−-decay scheme was considerably extended, and various sequences of the levels were interpreted as resulting from the prolate, oblate, and triaxial nuclear shapes. Some of the β− decays were considered as the allowed Gamow-Teller transitions. The experimental distribution of Gamow-Teller streng…
Detailed spectroscopy of the neutron-deficient bismuth isotopes ¹⁹³,¹⁹⁵Bi
2015
Two experiments aiming to study the shape coexistence and competing structures in 193Bi and 195Bi isotopes have been performed at the Accelerator laboratory of the University of Jyv askyl a, Finland (JYFL). Many new states have been found, hugely extending the previously known level schemes for both isotopes. The i13=2 bands were extended up to I = 45/2+ in both the 193;195Bi isotopes. In case of 193Bi, the I = 31/2+ member of the i13=2 band was found to de-excite also to a long-lived isomeric state. This link determines the energy of the isomeric state to be 2350(1) keV and suggests a spin and parity of 29/2+. The half-life of the isomeric state was measured to be 85(3) s. A level structur…
Measurement of the double-beta decay half-life and search for the neutrinoless double-beta decay of Ca48 with the NEMO-3 detector
2016
The NEMO-3 experiment at the Modane Underground Laboratory investigates the double-beta decay of Ca48. Using 5.25 yr of data recorded with a 6.99 g sample of Ca48, approximately 150 double-beta decay candidate events are selected with a signal-to-background ratio greater than 3. The half-life for the two-neutrino double-beta decay of Ca48 is measured to be T2ν1/2=[6.4+0.7−0.6(stat)+1.2−0.9(syst)]×1019 yr. A search for neutrinoless double-beta decay of Ca48 yields a null result, and a corresponding lower limit on the half-life is found to be T0ν1/2>2.0×1022 yr at 90% confidence level, translating into an upper limit on the effective Majorana neutrino mass of ⟨mββ⟩<6.0–26 eV, with the rang…
Laser assisted decay spectroscopy at the CRIS beam line at ISOLDE
2012
A new collinear resonant ionization spectroscopy (Cris)beam line has recently been installed at Isolde, Cern utilising lasers to combine collinear laser spectroscopy and resonant ionization spectroscopy. The combined technique offers the ability to purify an ion beam that is heavily contaminated with radioactive isobars, including the ground state of an isotope from its isomer, allowing sensitive secondary experiments to be performed. A new programme aiming to use the Cris technique for the separation of nuclear isomeric states for decay spectroscopy will commence in 2011. A decay spectroscopy station, consisting of a rotating wheel implantation system for alpha decay spectroscopy, and thre…
Cytoplasmic 5′-3′ exonuclease Xrn1p is also a genome-wide transcription factor in yeast
2014
The 5′ to 3′ exoribonuclease Xrn1 is a large protein involved in cytoplasmatic mRNA degradation as a critical component of the major decaysome. Its deletion in the yeast Saccharomyces cerevisiae is not lethal, but it has multiple physiological effects. In a previous study, our group showed that deletion of all tested components of the yeast major decaysome, including XRN1, results in a decrease in the synthetic rate and an increase in half-life of most mRNAs in a compensatory manner. Furthermore, the same study showed that the all tested decaysome components are also nuclear proteins that bind to the 5′ region of a number of genes. In the present work, we show that disruption of Xrn1 activi…
Searches for lepton number violation and resonances in K± → πμμ decays
2017
The NA48/2 experiment at CERN collected a large sample of charged kaon decays to final states with multiple charged particles in 2003–2004. A new upper limit on the rate of the lepton number violating decay K±→π∓μ±μ± is reported: B(K±→π∓μ±μ±)<8.6×10−11 at 90% CL. Searches for two-body resonances X in K±→πμμ decays (such as heavy neutral leptons N4 and inflatons χ ) are also presented. In the absence of signals, upper limits are set on the products of branching fractions B(K±→μ±N4)B(N4→πμ) and B(K±→π±X)B(X→μ+μ−) for ranges of assumed resonance masses and lifetimes. The limits are in the (10−11,10−9) range for resonance lifetimes below 100 ps.