ترغب بنشر مسار تعليمي؟ اضغط هنا

In-beam gamma-ray spectroscopy of 35Mg and 33Na

186   0   0.0 ( 0 )
 نشر من قبل Alexandra Gade
 تاريخ النشر 2011
  مجال البحث
والبحث باللغة English




اسأل ChatGPT حول البحث

Excited states in the very neutron-rich nuclei 35Mg and 33Na were populated in the fragmentation of a 38Si projectile beam on a Be target at 83 MeV/u beam energy. We report on the first observation of gamma-ray transitions in 35Mg, the odd-N neighbor of 34Mg and 36Mg, which are known to be part of the Island of Inversion around N = 20. The results are discussed in the framework of large- scale shell-model calculations. For the A = 3Z nucleus 33Na, a new gamma-ray transition was observed that is suggested to complete the gamma-ray cascade 7/2+ --> 5/2+ --> 3/2+ gs connecting three neutron 2p-2h intruder states that are predicted to form a close-to-ideal K = 3/2 rotational band in the strong-coupling limit.



قيم البحث

اقرأ أيضاً

The odd-$Z$ $^{251}$Md nucleus was studied using combined $gamma$-ray and conversion-electron in-beam spectroscopy. Besides the previously observed rotational band based on the $[521]1/2^-$ configuration, another rotational structure has been identif ied using $gamma$-$gamma$ coincidences. The use of electron spectroscopy allowed the rotational bands to be observed over a larger rotational frequency range. Using the transition intensities that depend on the gyromagnetic factor, a $[514]7/2^-$ single-particle configuration has been inferred for this band, i.e., the ground-state band. A physical background that dominates the electron spectrum with an intensity of $simeq$ 60% was well reproduced by simulating a set of unresolved excited bands. Moreover, a detailed analysis of the intensity profile as a function of the angular momentum provided a method for deriving the orbital gyromagnetic factor, namely $g_K = 0.69^{+0.19}_{-0.16}$ for the ground-state band. The odd-$Z$ $^{249}$Md was studied using $gamma$-ray in-beam spectroscopy. Evidence for octupole correlations resulting from the mixing of the $Delta l = Delta j = 3$ $[521]3/2^-$ and $[633]7/2^+$ Nilsson orbitals were found in both $^{249,251}$Md. A surprising similarity of the $^{251}$Md ground-state band transition energies with those of the excited band of $^{255}$Lr has been discussed in terms of identical bands. Skyrme-Hartree-Fock-Bogoliubov calculations were performed to investigate the origin of the similarities between these bands.
Excited states in the neutron-rich N=38,36 nuclei uc{60}{Ti} and uc{58}{Ti} were populated in nucleon-removal reactions from uc{61}{V} projectiles at 90~MeV/nucleon. The gamma-ray transitions from such states in these Ti isotopes were detected wit h the advanced gamma-ray tracking array GRETINA and were corrected event-by-event for large Doppler shifts (v/c sim 0.4) using the gamma-ray interaction points deduced from online signal decomposition. The new data indicate that a steep decrease in quadrupole collectivity occurs when moving from neutron-rich N=36,38 Fe and Cr toward the Ti and Ca isotones. In fact, uc{58,60}{Ti} provide some of the most neutron-rich benchmarks accessible today for calculations attempting to determine the structure of the potentially doubly-magic nucleus uc{60}{Ca}.
The fusion and transfer induced fission reaction $^{9}$Be($^{238}$U,~f) with 6.2 MeV/u beam energy, using a unique setup consisting of AGATA, VAMOS++ and EXOGAM detectors, was used to populate through the fission process and study the neutron-rich $^ {119,121}$In isotopes. This setup enabled the prompt-delayed $gamma$-ray spectroscopy of isotopes in the time range of $100~rm{ns} - 200~murm{s}$. In the odd-$A$ $^{119,121}$In isotopes, indications of a short half-life $19/2^{-}$ isomeric state, in addition to the previously known $25/2^{+}$ isomeric state, were observed from the present data. Further, new prompt transitions above the $25/2^{+}$ isomer in $^{121}$In were identified along with reevaluation of its half-life. The experimental data were compared with the theoretical results obtained in the framework of large-scale shell-model calculations in a restricted model space. The $langle pi g_{9/2} u h_{11/2};I arrowvert hat{mathcal{H}}arrowvert pi g_{9/2} u h_{11/2};Irangle$ two-body matrix elements of residual interaction were modified to explain the excitation energies and the $B(E2)$ transition probabilities in the neutron-rich In isotopes. The (i) decreasing trend of $E(29/2^{+}) - E(25/2^{+})$ in odd-In (with dominant configuration $pi g_{9/2}^{-1} u h_{11/2}^{-2}$ and maximum aligned spin of $29/2^{+}$) and (ii) increasing trend of $E(27/2^{+}) - E(23/2^{+})$ in odd-Sb (with dominant configuration $pi g_{7/2}^{+1} u h_{11/2}^{-2}$ and maximum aligned spin of $27/2^{+}$) with increasing neutron number could be understood as a consequence of hole-hole and particle-hole interactions, respectively.
Background: In the island of inversion, ground states of neutron-rich $sd$-shell nuclei exhibit strong admixtures of intruder configurations from the $fp$ shell. The nucleus $^{30}$Mg, located at the boundary of the island of inversion, serves as a c ornerstone to track the structural evolution as one approaches this region. Purpose: Spin-parity assignments for excited states in $^{30}$Mg, especially negative-parity levels, have yet to be established. In the present work, the nuclear structure of $^{30}$Mg was investigated by in-beam $gamma$-ray spectroscopy mainly focusing on firm spin-parity determinations. Method: High-intensity rare-isotope beams of $^{31}$Mg, $^{32}$Mg, $^{34}$Si, and $^{35}$P bombarded a Be target to induce nucleon removal reactions populating states in $^{30}$Mg. $gamma$ rays were detected by the state-of-the-art $gamma$-ray tracking array GRETINA. For the direct one-neutron removal reaction, final-state exclusive cross sections and parallel momentum distributions were deduced. Multi-nucleon removal reactions from different projectiles were exploited to gain complementary information. Results: With the aid of the parallel momentum distributions, an updated level scheme with revised spin-parity assignments was constructed. Spectroscopic factors associated with each state were also deduced. Conclusions: Results were confronted with large-scale shell-model calculations using two different effective interactions, showing excellent agreement with the present level scheme. However, a marked difference in the spectroscopic factors indicates that the full delineation of the transition into the island of inversion remains a challenge for theoretical models.
148 - K. Hosomi , T. Ma , S. Ajimura 2015
Level structure of the $^{12}_{Lambda}$C hypernucleus was precisely determined by means of $gamma$-ray spectroscopy. We identified four $gamma$-ray transitions via the $^{12}$C$(pi^{+},K^{+}gamma)$ reaction using a germanium detector array, Hyperball 2. The spacing of the ground-state doublet $(2^{-}_{1},1^{-}_{1})$ was measured to be $161.5pm0.3text{(stat)}pm0.3text{(syst)}$,keV from the direct $M1$ transition. Excitation energies of the $1^{-}_{2}$ and $1^{-}_{3}$ states were measured to be $2832pm3pm4$,keV and $6050pm8pm7$,keV, respectively. The obtained level energies provide definitive references for the reaction spectroscopy of $Lambda$ hypernuclei.
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