ترغب بنشر مسار تعليمي؟ اضغط هنا

Investigation of low spin states in 48-Cr with the MINIBALL spectrometer

56   0   0.0 ( 0 )
 نشر من قبل Karsten Jessen
 تاريخ النشر 2003
  مجال البحث
والبحث باللغة English
 تأليف K. Jessen




اسأل ChatGPT حول البحث

Low spin states in the self-conjugate even-even nucleus 48-Cr were investigated using the MINIBALL gamma-ray spectrometer. At the FN tandem accelerator in Cologne the 46-Ti(3-He,n) reaction was used for the measurement of gamma-gamma coincidences for an excitation function from 7 to 12 MeV beam energy. 17 excited states were observed, nine for the first time by means of gamma-ray spectroscopy, and new spin assignments were made. No excited states apart from the ground band were observed below 3.4 MeV.

قيم البحث

اقرأ أيضاً

The backbending phenomenon in $^{48}$Cr has been investigated using the recently developed Projected Configuration Interaction (PCI) method, in which the deformed intrinsic states are directly associated with shell model (SM) wavefunctions. Two previ ous explanations, (i) $K=0$ band crossing, and (ii) $K=2$ band crossing have been reinvestigated using PCI, and it was found that both explanations can successfully reproduce the experimental backbending. The PCI wavefunctions in the pictures of $K=0$ band crossing and $K=2$ band crossing are highly overlapped. We conclude that there are no unique intrinsic states associated with the yrast states after backbending in $^{48}$Cr.
Using particle-$gamma$ coincidences we have studied the population of final states after the emission of 2 $alpha$-particles and of $^{8}$Be in nuclei formed in $^{32}$S+$^{24}$Mg reactions at an energy of $textrm{E}_{rm L}(^{32}textrm{S}) = 130 {rm MeV}$. The data were obtained in a setup consisting of the GASP $gamma$-ray detection array and the multidetector array ISIS. Particle identification is obtained from the $Delta$E and E signals of the ISIS silicon detector telescopes, the $^{8}$Be being identified by the instantaneous pile up of the $Delta$E and E pulses. $gamma$-ray decays of the $^{48}$Cr nucleus are identified with coincidences set on 2 $alpha$-particles and on $^{8}$Be. Some transitions of the side-band with $K^pi=4^{-}$ show stronger population for $^{8}$Be emission relative to that of 2 $alpha$-particles (by a factor $1.5-1.8$). This observation is interpreted as due to an enhanced emission of $^{8}$Be into a more deformed nucleus. Calculations based on the extended Hauser-Feshbach compound decay formalism confirm this observation quantitatively.
Proton-scattering experiments followed by the coincident spectroscopy of $gamma$ rays have been performed at the Institute for Nuclear Physics of the University of Cologne to excite low-spin states in $^{112}$Sn and $^{114}$Sn, to determine their lif etimes and extract reduced transitions strengths $B(Pi L)$. The combined spectroscopy setup SONIC@HORUS has been used to detect the scattered protons and the emitted $gamma$ rays of excited states in coincidence. The novel $(p,pgamma)$ DSA coincidence technique was employed to measure sub-ps nuclear level lifetimes. 74 level lifetimes $tau$ of states with $J = 0 - 6$ were determined. In addition, branching ratios were deduced which allowed the investigation of the intruder configuration in both nuclei. Here, $sd$ IBM-2 mixing calculations were added which support the coexistence of the two configurations. Furthermore, members of the expected QOC quintuplet are proposed in $^{114}$Sn for the first time. The $1^-$ candidate in $^{114}$Sn fits perfectly into the systematics observed for the other stable Sn isotopes. The $E2$ transition strengths observed for the low-spin members of the so-called intruder band support the existence of shape coexistence in $^{112,114}$Sn. The collectivity in this configuration is comparable to the one observed in the Pd nuclei, i.e. the 0p-4h nuclei. Strong mixing between the $0^+$ states of the normal and intruder configuration might be observed in $^{114}$Sn. The general existence of QOC states in $^{112,114}$Sn is supported by the observation of QOC candidates with $J eq 1$.
Low-spin states of 157Dy have been studied using the JUROGAM II array, following the 155Gd ({alpha}, 2n) reaction at a beam energy of 25 MeV. The level scheme of 157Dy has been expanded with four new bands. Rotational structures built on the [523]5/2 - and [402]3/2+ neutron orbitals constitute new additions to the level scheme as do many of the inter- and intra-band transitions. This manuscript also reports the observation of cross I- to (I-1)- and I- to (I-1)+ E1 dipole transitions inter-linking structures built on the [523]5/2- (band 5) and [402]3/2+ (band 7) neutron orbitals. These interlacing band structures are interpreted as the bands of parity doublets with simplex quantum number s = -i related to possible octupole correlations.
In this article a method for lifetime measurements in the sub-picosecond regime via the Doppler-shift attenuation method (DSAM) following the inelastic proton scattering reaction is presented. In a pioneering experiment we extracted the lifetimes of 30 excited low-spin states of $^{96}$Ru, taking advantage of the coincident detection of scattered protons and de-exciting $gamma$-rays as well as the large number of particle and $gamma$-ray detectors provided by the SONIC@HORUS setup at the University of Cologne. The large amount of new experimental data shows that this technique is suited for the measurement of lifetimes of excited low-spin states, especially for isotopes with a low isotopic abundance, where $(n,n^{prime}gamma$) or - in case of investigating dipole excitations - ($gamma,gamma^{prime}$) experiments are not feasible due to the lack of sufficient isotopically enriched target material.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا