اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدInverse-kinematics proton scattering on $^{50}$Ca: Determining effective charges using complementary probes
49
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We have performed measurements of the $0_mathrm{g.s.}^+ rightarrow 2_1^+$ excitations in the neutron-rich isotopes $^{48,50}$Ca via inelastic proton scattering on a liquid hydrogen target, using the GRETINA $gamma$-ray tracking array. A comparison of the present results with those from previous measurements of the lifetimes of the $2_1^+$ states provides us the ratio of the neutron and proton matrix elements for the $0_mathrm{g.s.}^+ rightarrow 2_1^+$ transitions. These results allow the determination of the ratio of the proton and neutron effective charges to be used in shell model calculations of neutron-rich isotopes in the vicinity of $^{48}$Ca.
قيم البحث
اقرأ أيضاً
Background: Thick-target-induced nucleon-adding transfer reactions onto energetic rare-isotope beams are an emerging spectroscopic tool. Their sensitivity to single-particle structure complements one-nucleon removal reaction capabilities in the quest
to reveal the evolution of nuclear shell structure in very exotic nuclei. Purpose: To add intermediate-energy, carbon-target-induced one-proton pickup reactions to the arsenal of $gamma$-ray tagged direct reactions applicable in the regime of low beam intensities and to apply these for the first time to $fp$-shell nuclei. Methods: Inclusive and partial cross sections were measured for the $ uc{12}{C}( uc{48}{Cr}, uc{49}{Mn}+gamma)$X and $ uc{12}{C}( uc{50}{Fe}, uc{51}{Co}+gamma)$X proton pickup reactions at 56.7 and 61.2 MeV/nucleon, respectively, using coincident particle-$gamma$ spectroscopy at the NSCL. The results are compared to reaction theory calculations using $fp$-shell-model nuclear structure input. For comparison with our previous work, the same reactions were measured on uc{9}{Be} targets. Results: The measured partial cross sections confirm the specific population pattern predicted by theory, with pickup into high-$ell$ orbitals being strongly favored; driven by linear and angular momentum matching. Conclusion: Carbon target-induced pickup reactions are well-suited, in the regime of modest beam intensity, to study the evolution of nuclear structure, with specific sensitivities that are well described by theory.
Absolute differential cross sections for elastic $p^7$Be and $p^8$B small-angle scattering were measured in inverse kinematics at an energy of 0.7 GeV/u at GSI Darmstadt. The hydrogen-filled ionization chamber IKAR was used as an active target to det
ect the recoil protons. The projectile tracking and isotope identification were performed with multi-wire proportional chambers and scintillation detectors. The measured cross sections were analysed using the Glauber multiple-scattering theory. The root-mean-square (rms) nuclear matter radii $R_{rm m} = 2.42 (4)$ fm for $^7$Be and $R_{rm m} = 2.58 (6)$ fm for $^8$B were obtained. The radial density distribution deduced for $^8$B exhibits a proton halo structure with the rms halo radius $R_{rm h} = 4.24 (25)$ fm. A comparison of the deduced experimental radii is displayed with existing experimental and theoretical data.
Excited states of the neutron-rich isotopes $^{42,44}$S and $^{41,43}$P have been studied via inverse-kinematics proton scattering from a liquid hydrogen target, using the GRETINA $gamma$-ray tracking array to extract inelastic scattering cross secti
ons. Deformation lengths of the $2^+_1$ excitations in $^{42,44}$S have been determined and, when combined with deformation lengths determined with electromagnetic probes, yield the ratio of neutron-to-proton matrix elements $M_n/M_p$ for the $2^+_1$ excitations in these nuclei. The present results for $^{41,43}$P$(p,p)$ are used to compare two shell model interactions, SDPF-U and SDPF-MU. As in a recent study of $^{42}$Si, the present results on $^{41,43}$P favor the SDPF-MU interaction.
The absolute differential cross sections for small-angle proton elastic scattering off the nuclei $^{12,14-17}$C have been measured in inverse kinematics at energies near 700 MeV/u at GSI Darmstadt. The hydrogen-filled ionization chamber IKAR served
simultaneously as a gas target and a detector for the recoil protons. The projectile scattering angles were measured with multi-wire tracking detectors. The radial nuclear matter density distributions and the root-mean-square nuclear matter radii were deduced from the measured cross sections using the Glauber multiple-scattering theory. A possible neutron halo structure in $^{15}$C, $^{16}$C and $^{17}$C is discussed. The obtained data show evidence for a halo structure in the $^{15}$C nucleus.
The spinflip M1 resonance in the doubly magic nucleus $^{48}$Ca, dominated by a single transition, serves as a reference case for the quenching of spin-isospin modes in nuclei. The aim of the present work is a search for weak M1 transitions in $^{48}
$Ca with a high-resolution (p,p) experiment at 295 MeV and forward angles including 0 degree and a comparison to results from a similar study using backward-angle electron scattering at low momentum transfers in order to estimate their contribution to the total B(M1) strength. M1 cross sections of individual peaks in the spectra are deduced with a multipole decomposition analysis. The corresponding reduced B(M1) transition strengths are extracted following the approach outlined in J. Birkhan et al., Phys. Rev. C 93, 041302(R) (2016). In total, 29 peaks containing a M1 contribution are found in the excitation energy region 7 - 13 MeV. The resulting B(M1) strength distribution compares well to the electron scattering results considering different factors limiting the sensitivity in both experiments and the enhanced importance of mechanisms breaking the proportionality of nuclear cross sections and electromagnetic matrix elements for weak transitions as studied here. The total strength of 1.19(6) $mu_N^2$ deduced assuming a non-quenched isoscalar part of the (p,p) cross sections agrees with the (e,e) result of 1.21(13) $mu_N^2$. A binwise analysis above 10 MeV provides an upper limit of 1.62(23) $mu_N^2$. The present results confirm that weak transitions contribute about 25% to the total B(M1) strength in $^{48}$Ca and the quenching factors of GT and spin-M1 strength are comparable in fp-shell nuclei. Thus, the role of of meson exchange currents seems to be neglible, in contrast to sd-shell nuclei.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
