Search results for "ISOTOPES"
showing 10 items of 1216 documents
β-decay half-lives andβ-delayed neutron emission probabilities of nuclei in the regionA≲110, relevant for the r process
2009
Measurements of $\ensuremath{\beta}$-decay properties of $A\ensuremath{\lesssim}110$ r-process nuclei have been completed at the National Superconducting Cyclotron Laboratory at Michigan State University. $\ensuremath{\beta}$-decay half-lives for $^{105}\mathrm{Y}$, $^{106,107}\mathrm{Zr}$, and $^{111}\mathrm{Mo}$, along with $\ensuremath{\beta}$-delayed neutron emission probabilities of $^{104}\mathrm{Y}$, $^{109,110}\mathrm{Mo}$ and upper limits for $^{105}\mathrm{Y}$, $^{103\ensuremath{-}107}\mathrm{Zr}$, and $^{108,111}\mathrm{Mo}$ have been measured for the first time. Studies on the basis of the quasi-random-phase approximation are used to analyze the ground-state deformation of these…
Search for very long-lived isomers in the hafnium-tungsten region
2000
Targets of ${}^{48}\mathrm{Ca}$ have been bombarded with ${}^{134,136}\mathrm{Xe}$ beams as part of a search for long-lived, high-K states in well-deformed nuclei with $A\ensuremath{\approx}180.$ Several known isomers were observed by off-line \ensuremath{\gamma}-ray detection, and limits have been established for high-K isomer production in various isotopes of hafnium $(A=175--178),$ tantalum $(A=177--181),$ and tungsten $(A=177--181).$
Comparison of T[sub z] = ±1→0 GT Transitions
2010
Gamow‐Teller (GT) transitions can be studied in both β‐decay and charge exchange(CE) reactions. If isospin is a good quantum number, then the Tz = −1→0 and Tz = +1→0 GT mirror transitions, are identical. Therefore, a comparison of the results from studies of β decay and CE should shed light on this assumption. Accordingly we have studied the β decay of the Tz = −1 fp‐shell nuclei, 54Ni, 50Fe, 46Cr, and 42Ti, produced in fragmentation and we have compared our results with the spectra from (3He, t) measurements on the mirror Tz = +1 target nuclei studied in high resolution at RCNP, Osaka. The β‐decay experiments were performed as part of the STOPPED beam RISING campaign at GSI.
Gamow-Teller Transitions Studied in ([sup 3]He, t) Reaction and Analogous β decay
2010
Due to the simplicity of the στ operator that causes Gamow‐Teller (GT) transitions, they are the most popular nuclear weak process in the Universe. The GT transitions in pf‐shell nuclei, for example, starting from stable Tz = +1 and proton‐rich Tz = +1 nuclei, where Tz = (N−Z)/2, play important roles in the supernova‐explosion or rp‐process nucleosynthesis. In the β‐decay study of pf‐shell nuclei, half‐lives can be measured rather accurately. On the other hand, in a high‐resolution (3He, t) charge‐exchange reaction at 0°, individual GT transitions up to high excitations can be studied. In order to derive reliable GT transition strengths B(GT), we present a unique analysis that combines the …
Decay Spectroscopy for Nuclear Astrophysics: β-delayed Proton Decay
2011
In several radiative proton capture reactions important in novae and XRBs, the resonant parts play the capital role. We use decay spectroscopy techniques to find these resonances and study their properties. We have developed techniques to measure beta- and beta-delayed proton decay of sd-shell, proton-rich nuclei produced and separated with the MARS recoil spectrometer of Texas A&M University. The short-lived radioactive species are produced in-flight, separated, then slowed down (from about 40 MeV/u) and implanted in the middle of very thin Si detectors. This allows us to measure protons with energies as low as 200 keV from nuclei with lifetimes of 100 ms or less. At the same time we measu…
Decay spectroscopy of neutron-rich nuclei with A $$ \simeq $$ 100
2012
We review structure data obtained by decay spectroscopy of neutron-rich nuclei of mass close to 100. Emphasis is put on the contribution of experiments at IGISOL in the nineties. They confirmed the earlier postulated shape coexistence in the fast shape-transition region between N = 58 (spherical ground states and low collectivity) and N = 60 (strong axial deformation). A detailed spectroscopic study of the A = 99 chain established the upper-Z limit of the N = 56 shell closure region with 99Nb, owing to striking similarities with 97Y. A consequence of the N = 56 closure is that the s 1/2 odd-neutron becomes the ground state of the most neutron-rich N = 57 isotones, starting with 99Mo, instea…
New Features in the Systematics of Low‐Spin States in Even 106‐120Cd
1991
Low‐spin states in even 106‐112Cd and 116Cd were investigated by in‐beam and off‐beam γ‐ray and conversion‐electron spectroscopy. New spin assignments and decay branching ratios for the levels in 106Cd,108Cd,110Cd and 112Cd were obtained. From the new systematical data for the even 106‐120Cd, it is inferred that two sets of low‐lying 0+ states cross between 114Cd and 116Cd. One of these sets appears to have features of both intruder and two‐quadrupole‐phonon states.
The shape transition in the neutron-rich yttrium isotopes and isomers
2007
Abstract Laser spectroscopy has been used to study 86–90,92–102Y and isomeric states of 87–90,93,96,97,98Y. Nuclear charge radii differences, magnetic dipole and electric quadrupole moments have been obtained. Information on the nature of the Z ≈ 40 , N ≈ 60 sudden onset of deformation has been derived from all three parameters. It is seen that with increasing neutron number from the N = 50 shell closure that the nuclear deformation becomes increasingly oblate and increasingly soft. At N = 60 a transition to a strongly deformed rigid prolate shape occurs but prior to this, although the nuclear deformation is increasing with N, a proportionate increase in softness is also observed.
First observation of nonyrast levels inZr103and level systematics ofN= 63 Sr, Zr, and Mo isotones
1996
The {beta} decay of the very-neutron-rich nucleus {sup 103}Y has been studied at the isotope separator IGISOL, allowing for the first time the observation of nonyrast levels in its daughter {sub 40}{sup 103}Zr{sub 63}. The level structure is similar to that of its isotones {sup 101}Sr and {sup 105}Mo, suggesting a large ground-state deformation of {beta}{approx_equal} 0.4. Level systematics allows for new level assignments in both {sup 103}Zr and {sup 105}Mo. {copyright} {ital 1996 The American Physical Society.}
Heavy isotopes of actinium: 229Ac, 230Ac, 231Ac and 232Ac
1973
Abstract By irradiation of 232Th with 150-MeV bremsstrahlung and with 14-MeV neutrons, three new neutron-rich isotopes of actinium, 230Ac, 231Ac and 232Ac, were produced and identified and the previously reported isotope, 229Ac, was confirmed. The actinium isotopes were chemically isolated by a fast procedure based on elution with α-hydroxyisobutyric acid from cation exchange resins. For 229Ac, a half-life of 62·7 ± 0·5 min and a β-ray energy of 1·14 ± 0·15 MeV were found; 35 γ-rays were observed, the strongest ones with the following energies and relative intensities: 135·3(34), 146·4(35), 164·6(100), 252·2(24), 261·9(39), 317·0(23), 539·9(20), 569·1(91), and 605·2 keV(23). For 230Ac, a ha…