Search results for "Excitation"
showing 10 items of 1290 documents
Characterizing the atomic mass surface beyond the proton drip line viaα-decay measurements of theπs1/2ground state of165Re and theπh11/2isomer in161Ta
2012
The α-decay chains originating from the πs1/2 and πh11/2 states in 173Au have been investigated following fusion-evaporation reactions. Four generations of α radioactivities have been correlated with 173Aum leading to a measurement of the α decay of 161Tam. It has been found that the known α decay of 161Ta, which was previously associated with the decay of the ground state, is in fact the decay of an isomeric state. This work also reports on the first observation of prompt γ rays feeding the ground state of 173Au. This prompt γ radiation was used to aid the study of the α-decay chain originating from the πs1/2 state in 173Au. Three generations of α decays have been correlated with this stat…
Dipole excitations of neutron-proton asymmetric nuclei
2004
Dipole excitations of unstable short-lived nuclei has been investigated experimentally by utilizing the electromagnetic-excitation process with high-energy secondary beams. From an exclusive measurement of the neutron-decay channels, differential cross sections with respect to excitation energy, which are directly related to the photo-absorption cross section and accordingly to the dipole-strength function, have been derived. Light neutron-rich nuclei in the mass range fromA = 11 toA = 23 with mass-over-charge ratios up toA/Z≈ 2.8 have been investigated systematically. Much in contrast to stable nuclei, low-lying dipole excitations well below the giant dipole resonance region have been obse…
Measurement of the dipole response of neutron-rich nuclei in the A∼20 region
2002
Abstract Coulomb break up of the neutron-rich 15,17 C and 17–22 O isotopes has been studied experimentally using secondary beams at energies of 500–600 MeV/u. A comparison between differential cross sections, d σ/ d E ∗ , with that obtained from a binary model shows that the main ground-state configuration of 15 C is 14 C(0 + )⊗ ν S 1/2 as expected. For 17 C, our preliminary data analysis reveals that the predominant (∼64%) configuration of the ground state is 16 C(2 + )⊗ ν s , d . For 17–22 O, the low-lying E1 strength amounts up to about 12% of the energy weighted sum rule strength depending on neutron number. The energy weighted E1 strength (integrated up to 15 MeV excitation energy) inc…
Electromagnetic excitation of the two-phonon giant dipole resonance
1994
Abstract The nuclear response of 136 Xe and 208 Pb to electromagnetic excitation was studied in peripheral, near-relativistic heavy-ion collisions. Large cross sections were observed for the one-phonon and two-phonon isovector giant dipole resonance. The results, in particular the unexpectedly large strength found for the double giant dipole resonance, are discussed and compared to that of other recent measurements.
Dipole response of neutron-rich Sn isotopes
2007
The neutron-rich isotopes 129–133Sn were studied in a Coulomb excitation experiment at about 500 AMeV using the FRS-LAND setup at GSI. From the exclusive measurement of all projectile-like particles following the excitation and decay of the projectile in a high-Z target, the energy differential cross section can be extracted. At these beam energies dipole transitions are dominating, and within the semi-classical approach the Coulomb excitation cross sections can be transformed into photoabsorption cross sections. In contrast to stable Sn nuclei, a substantial fraction of dipole strength is observed at energies below the giant dipole resonance (GDR). For 130Sn and 132Sn this strength is loca…
On the decay of compound nuclei following alpha-particle and12C induced reactions
1981
Multiple coincidence rates have been measured using a detector system consisting of a Ge(Li) spectrometer and eight NaI(Tl) or eight liquid scintillators. Reactions induced byα-particles with energies of 51–55 MeV and 118 MeV12C ions are studied. The data are analysed to give the first and second central moments of the distribution of the number ofγ-rays feeding individual levels in the final nuclei. When these numbers are compared to spin distributions calculated with the statistical model code GROGI the relative importance of dipole and quadrupole deexcitation modes can be ascertained. In particular, in the122Te(α, 4n)122Xe reaction theγ-decay prior to the entry into the ground band is we…
Neutron configurations inPd113
2014
Excited states in $^{113}\mathrm{Pd}$, populated in ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of $^{113}\mathrm{Rh}$ and in spontaneous fission of $^{248}\mathrm{Cm}$ and $^{252}\mathrm{Cf}$, have been studied by means of $\ensuremath{\gamma}$ spectroscopy at the IGISOL facility of Jyv\"askyl\"a University and using large arrays of Ge detectors (Eurogam2 and Gammasphere, respectively). The position of the ${11/2}^{\ensuremath{-}}$ yrast excitation in $^{113}\mathrm{Pd}$, proposed recently at 166.1 keV by other authors, has been corrected to 98.9 keV. The decay of this level has been discussed to explain the observed transition intensities. The ${7/2}^{\ensuremath{-}}$ member of the yras…
The 1.5GeV harmonic double-sided microtron at Mainz University
2008
Abstract At the Institut fur Kernphysik of Mainz University a harmonic double-sided microtron (HDSM) has been built to extend the experimental capabilities for nuclear and particle physics experiments to higher excitation energies. This novel microtron variant accelerates the 0.855 GeV continuous wave (cw) electron beam of the established three-staged race track microtron (RTM) cascade MAMI B up to 1.5 GeV. It consists of two normal conducting linear accelerators (linacs) through which the electrons are guided up to 43 times by a pair of 90°-bending magnets at each end. For beam dynamical reasons the linacs operate at the harmonic frequencies of 4.90 and 2.45 GHz. The extended facility is c…
Low energy reactions with radioactive ions at REX-ISOLDE-the 9Li + 2H case
2005
19 pages, 12 figures, 2 tables.-- PACS nrs.: 25.60.-t; 25.45.-z; 27.20.+n.-- et al. ISOLDE Collaborattion and REX-ISOLDE Collaboration.
Mirror symmetry at high spin in51Feand51Mn
2000
Gamma decays from excited states in the ${T}_{z}=\ensuremath{-}\frac{1}{2}$ nucleus ${}^{51}$Fe have been observed for the first time. The differences in excitation energies as compared with those of the mirror partner, ${}^{51}$Mn, have been interpreted in terms of Coulomb effects and the resulting Coulomb energy differences (CED) can be understood intuitively in terms of particle-alignment effects. A new CED effect has been observed, in which different CED trends have been measured for each signature of the rotational structures that characterize these mid-${f}_{7/2}$ shell nuclei. Large-scale $\mathrm{fp}$-shell model calculations have been used to compute the trends of the CED as a func…