Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userHigh spin states of $^{204}$At: search for isomeric states and evaluation of shears band structure
139
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
High spin states of neutron deficient Trans-Lead nucleus $^{204}$At were populated up to $E_x sim 8,{rm MeV}$ through the $^{12}$C + $^{197}$Au fusion evaporation reaction. Decay of the high spin states including prompt and delayed gamma ray emission were studied to understand the underlying nuclear structure. The level scheme, which was partly known from earlier studies, was extended further through our experiment and analysis of spin and parity of the associated levels. An isomeric $16^+$ level $(tau=52(5), {rm ns})$, corresponding to $M2$ transition, was established from our measurements. Attempts were made at interpretation of the excited states based on multi quasiparticle and hole structure involving $2f_{5/2}$, $1h_{9/2}$, and $1i_{13/2}$ shell model states, along with moderate core excitation. Magnetic dipole band structure over the spin parity range:~$16^+ - 23^+$, which was found in the earlier Gammasphere study, was confirmed and explored in more detail, including the missing cross-over $E2$ transitions. Band-crossing along the shears band was observed and compared with the evidence of similar phenomena in the neighboring neutron deficient $^{202}$Bi, $^{205}$Rn isotones and the neighbouring $^{203}$At isotope. Based on comparison of the measured $B(M1)/B(E2)$ values for transitions along the band with the semiclassical model based estimates, the shears band of $^{204}$At was firmly established along with the level scheme.
rate research
Read More
The isomeric and {beta} decays of the N = Z +2 nucleus 96Ag were investigated at NSCL. A cascade of {gamma}-ray transitions originating from the de-excitation of a {mu}s isomer was observed for the first time and was found in coincidence with two previously-known transitions with energies of 470 and 667 keV. The isomeric half-life was determined as 1.45(7) {mu}s, more precise than previously reported. The existence of a second, longer-lived {mu}s isomer, associated with a 743-keV transition, is also proposed here. Shell model results within the (p_{3/2}p_{1/2}f_{5/2}g_{9/2}) model space, using the jj44b interaction, reproduced level energies and isomeric decay half-lives reasonably well.
Neutron deficient isotopes of Francium (Z=87, N=121-123) as excited nuclei were produced in the fusion-evaporation reaction: 197Au(16O,xn)[213-x]Fr at 100 MeV. The gamma-rays from the residues were observed through the high sensitivity Germanium Clover detector array INGA. The decay of the high spin states and the isomeric states of the doubly-odd 208Fr nuclei, identified from the known sequence of ground state transitions, were observed. The half lives of the 194(2) keV isomeric transition, known from earlier observations, was measured to be 233(18) ns. A second isomeric transition at 383(2) keV and half life of 33(7) ns was also found. The measured half lives were compared with the corresponding single particle estimates, based on a the level scheme obtained from the experiment.
The discovery of naturally occurring long-lived isomeric states (t_1/2 > 10^8 yr) in the neutron-deficient isotopes 211,213,217,218Th [A. Marinov et al., Phys. Rev. C 76, 021303(R) (2007)] was reexamined using accelerator mass spectrometry (AMS). Because AMS does not suffer from molecular isobaric background in the detection system, it is an extremely sensitive technique. Despite our up to two orders of magnitude higher sensitivity we cannot confirm the discoveries of neutron-deficient thorium isotopes and provide upper limits for their abundances.
Decay spectroscopy of the odd-proton nuclei $^{249}$Md and $^{251}$Md has been performed. High-$K$ isomeric states were identified for the first time in these two nuclei through their electromagnetic decay. An isomeric state with a half-life of $2.4(3)$ ms and an excitation energy $geq 910$ keV was found in $^{249}$Md. In $^{251}$Md, an isomeric state with a half-life of $1.37(6)$ s and an excitation energy $geq 844$ keV was found. Similarly to the neighbouring $^{255}$Lr, these two isomeric states are interpreted as 3 quasi-particle high-$K$ states and compared to new theoretical calculations. Excited nuclear configurations were calculated within two scenarios: via blocking nuclear states located in proximity to the Fermi surface or/and using the quasiparticle Bardeen-Cooper-Schrieffer method. Relevant states were selected on the basis of the microscopic-macroscopic model with a deformed Woods-Saxon potential. The most probable candidates for the configurations of $K$-isomeric states in Md nuclei are proposed.
Neutron-rich nuclei were populated in a relativistic fission of 238U. Gamma-rays with energies of 135 keV and 184 keV were associated with two isomeric states in 121Pd and 117Ru. Half-lives of 0.63(5) microseconds and 2.0(3) micrisecondss were deduced and the isomeric states were interpreted in terms of deformed single-particle states.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
