Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userNew Experimentally Observable Gamma-ray Emissions from 241Am Nuclear Decay
123
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
With the high resolution of microcalorimeter detectors, previously unresolvable gamma-ray lines are now clearly resolvable. A careful measurement of 241Am decay with a large microcalorimeter array has yielded never before seen or predicted gamma lines at 207.72 +/- 0.02 keV and 208.21 +/- 0.01 keV. These have been made possible because of new microwave-multiplexing readout and improved analysis algorithms for microcalorimeters.
rate research
Read More
A new search for production of correlated e+e- pairs in the alpha decay of 241Am has been carried out deep underground at the Gran Sasso National Laboratory of the I.N.F.N. by using pairs of NaI(Tl) detectors of the DAMA/LIBRA set-up. The experimental data show an excess of double coincidences of events with energy around 511 keV in faced pairs of detectors, which are not explained by known side reactions. This measured excess gives a relative activity lambda = (4.70 pm 0.63) times 10^{-9} for the Internal Pair Production (IPP) with respect to alpha decay of 241Am; this value is of the same order of magnitude as previous determinations. In a conservative approach the upper limit lambda < 5.5 times 10^{-9} (90% C.L.) can be derived. It is worth noting that this is the first result on IPP obtained in an underground experiment, and that the lambda value obtained in the present work is independent on the live-time estimate.
Total absorption spectroscopy was used to investigate the beta-decay intensity to states above the neutron separation energy followed by gamma-ray emission in 87,88Br and 94Rb. Accurate results were obtained thanks to a careful control of systematic errors. An unexpectedly large gamma intensity was observed in all three cases extending well beyond the excitation energy region where neutron penetration is hindered by low neutron energy. The gamma branching as a function of excitation energy was compared to Hauser-Feshbach model calculations. For 87Br and 88Br the gamma branching reaches 57% and 20% respectively, and could be explained as a nuclear structure effect. Some of the states populated in the daughter can only decay through the emission of a large orbital angular momentum neutron with a strongly reduced barrier penetrability. In the case of neutron-rich 94Rb the observed 4.5% branching is much larger than the calculations performed with standard nuclear statistical model parameters, even after proper correction for fluctuation effects on individual transition widths. The difference can be reconciled introducing an enhancement of one order-of-magnitude in the photon strength to neutron strength ratio. An increase in the photon strength function of such magnitude for very neutron-rich nuclei, if it proved to be correct, leads to a similar increase in the (n,gamma) cross section that would have an impact on r-process abundance calculations.
The Mott polarimetry for T -Violation (MTV) experiment tests time-reversal symmetry in polarized nuclear beta decay by measuring an electrons transverse polarization as a form of angular asymmetry in Mott scattering using a thin metal foil. A Mott scattering analyzer system developed using a tracking detector to measure scattering angles offers better event selectivity than conventional counter experiments. In this paper, we describe a pilot experiment conducted at KEK-TRIAC using a prototype system with a polarized 8Li beam. The experiment confirmed the sound performance of our Mott analyzer system to measure T-violating triple correlation (R correlation), and therefore recommends its use in higher-precision experiments at the TRIUMF-ISAC.
The scandium isotopes 44,45Sc have been studied with the 45Sc(3He,alpha gamma)44Sc and 45Sc(3He,3He gamma)45Sc reactions, respectively. The nuclear level densities and gamma-ray strength functions have been extracted using the Oslo method. The experimental level densities are compared to calculated level densities obtained from a microscopic model based on BCS quasiparticles within the Nilsson level scheme. This model also gives information about the parity distribution and the number of broken Cooper pairs as a function of excitation energy. The experimental gamma-ray strength functions are compared to theoretical models of the E1, M1, and E2 strength, and to data from (gamma,n) and (gamma,p) experiments. The strength functions show an enhancement at low gamma energies that cannot be explained by the present, standard models.
The nuclear level density and the gamma-ray strength function have been determined for 43Sc in the energy range up to 2 MeV below the neutron separation energy using the Oslo method with the 46Ti(p,alpha)43Sc reaction. A comparison to 45Sc shows that the level density of 43Sc is smaller by an approximately constant factor of two. This behaviour is well reproduced in a microscopical/combinatorial model calculation. The gamma-ray strength function is showing an increase at low gamma-ray energies, a feature which has been observed in several nuclei but which still awaits theoretical explanation.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
