Nuclear structure study of ^{19,21}N nuclei by γ spectroscopy (original) (raw)
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Physical Review C, 2008
The structure of 19−22 N nuclei was investigated by means of in-beam γ -ray spectroscopic technique using fragmentation reactions of both stable and radioactive beams. Based on particle-γ and particle-γ γ coincidence data, level schemes are constructed for the neutron-rich nitrogen nuclei. The experimental results are compared with shell model calculations. The strength of the N = 14 and Z = 8 shell closures and the weakening of the shell model interaction WBT are discussed.
Measurement of (n,γ) reaction cross section of 186W-isotope at neutron energy of 20.02±0.58 MeV
2020
Institute for Plasma Research, Gandhinagar 382 428, India Department of Physics, The M S University of Baroda 390 002, India ITER-India, Gandhinagar 382 428, India Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India Department of Electrical Power Engineering, Brno University of Technology, Brno 61600, Czech Republic
New mass measurements of neutron-rich nuclei near N=20
Physics Letters B, 1991
The masses of 39 neutron-rich nuclei in the mass range 17-37 have been measured using a direct time-of-flight technique following the fragmentation of a 48Ca beam at 55 MeV/nucleon. The masses of 29'3°Ne, 34'35Mg and 36'37A1 are reported for the first time. The very. neutron-rich nuclei, 3133Na, are found to be 2-4 MeV less bound than previously believed. A comparison is made with recently available large scale shell model calculations encompassing thc deformed A ~ 32 nuclei. Conclusions are drawn regarding the extent of the region of deformation, which is found to include ~C~Ne.
Physics of Atomic Nuclei, 2007
We have measured deexcitation γ rays in the neutron-rich nuclei of 240U, 246Pu, and 250Cm produced by the (18O, 16O) two-neutron transfer reactions, in coincidence with the 16O particles using Si ΔE-E detectors. The γ rays in these nuclei were identified by selecting the kinetic energies of 16O particles, which correspond to the excitation energies in the residual nuclei below the neutron separation energies. The ground-state bands of 240U, 246Pu, and 250Cm were established up to 12+ states and the K π = 0- octupole band of 240U was established up to 9- states. The systematics of the moments of inertia of the ground-state bands for actinide nuclei shows that the deformed subshell closure at N = 152 is sustained for 96Cm isotopes and that it disappears for 94Pu isotopes.
Neutron emission from the compound nucleus 26Al
Physics Letters B, 1985
Neutron ume-of-fhght spectra have been measured m comodence with mdlvldual nucle~ produced in the fusmn reaction 14N + 12C induced by the bombardment of a 12C target with a 48 MeV 14N beam. Whereas for the residual nuclei 21Na(an), 2°Ne(apn) and 23Na(2pn), the observed neutron spectra are well reproduced m intensity and shape by statistical model calculations, ttusts not the case for the restdual nucleus 24Mg(pn) In order to reproduce the experimental neutron spectra, ~t seems necessary to assume that around an exotatlon energy of 16 to 18 MeV m 24Mg, gamma-ray emission is able to compete favourably agmnst particle decay.
Physical Review C, 1983
We measured neutron time-of-flight spectra from 90 MeV protons and 140 MeV alpha particles bombarding thin targets of Al, Ni, Zr, and Bi at laboratory angles between 20 and 135. The lowenergy (5 to 45 MeV) portions of the spectra were measured with 5 cm diameter by 5 cm deep NE-213 counters at 1 m flight paths with n-y pulse-shape discrimination. The high-energy (35 to 150 MeV) portions of the spectra were measured with 12.7 cm diameter by 10.2 cm deep NE-102 counters at flight paths of 2.0 to 5.0 m. The proton-induced measured neutron spectra reveal three distinct energy regions: a low-energy evaporation region, a high-energy region dominated by the quasifree scattering process, and an intermediate-energy region dominated by multistep, preequilibrium processes. In the latter two regions, the spectra show strong angular dependence. The alphaparticle induced neutron spectra show these same distinct energy regions plus an exponential falloff above the beam energy per nucleon. The neutron spectra are compared with earlier proton spectra produced also by 90 MeV protons and 140 MeV alpha particles. It is observed that the high-energy portions of the forward-angle neutron and proton cross sections are in ratios consistent with the idea that single nucleon-nucleon scattering dominates. For the heavy-mass targets, the low-energy evaporation regions show neutron yields larger than proton yields. The proton-to-neutron ratios observed in the high-energy continua are interpreted with a quasifree calculation fitted simultaneously to the proton and the neutron spectra. Preequilibrium calculations with the exciton model and the hybrid model reproduce the shape of the experimental angle-integrated energy spectra down to lower energies than the quasifree calculations. The exciton model calculations underestimate the magnitudes of the cross sections, while the hybrid model provides better absolute agreement. One of the preequilibrium calculations uses the method of Mantzouranis and Weidenmuller to predict angular distributions; we find that the predicted angular distributions overestimate the neutron yields at forward angles. The intranuclear-cascade model predicts proton-to-neutron ratios much smaller than experimentally observed in the high-energy forward-angle continua.
Nuclear Physics A, 2011
Reaction cross sections with various kinds of breakup channels for neutron-rich carbon isotopes 18-20 C and for 9 Be impinging on a liquid hydrogen target were investigated at 40 MeV/nucleon. The nuclides of interest were produced via projectile fragmentation from a 63 MeV/nucleon 40 Ar beam and were separated in flight at the RIKEN projectile fragment separator (RIPS). The combination of the large-acceptance superconducting TOF spectrometer, TOMBEE (TOF Mass analyzer for exotic BEam Experiment), with a liquid hydrogen target, CRYPTA (CRYogenic ProTon and Alpha target system), enables simultaneous measurements of several reaction channels: the reaction cross sections (σ R ), individual elemental fragmentation cross sections (σ Z ), charge-changing cross sections (σ cc ), neutron-removal cross sections (σ −xn ), and charge-pickup cross sections (σ Z+1 ) for 19,20 C; σ Z , σ −xn , and σ Z+1 for 18 C; and σ R for 9 Be. The present σ R of 9 Be on proton, σ R = 397 ± 23 mb, measured in the inverse kinematics, was consistent with the previous measurements using proton beams at different laboratories. The σ R of 19 C and 20 C on proton were determined to be σ R = 754 ± 22 mb and σ R = 791 ± 34 mb, respectively. Taking into account the beam energy and target dependence of σ R , the present σ R are found to be considerably enhanced compared with those measured at around 1 GeV/nucleon. The σ Z+1 appears to increase with the mass number of the projectiles, and it significantly contributes to σ R in the present energy range. The finite-range opticallimit and few-body Glauber model analyses were performed for σ R to study the nuclear matter density distributions and to derive the relative strength of the s-wave components of the valence neutrons in 19 C and 20 C. A neutron halo structure of 19 C is confirmed with an s-wave dominance of the valence neutron when the effect of the charge-pickup reaction is taken into account. The large σ −n of 19 C and σ −2n of 20 C also support the decoupled structures of 18 C + n and 18 C + 2n, respectively. The σ cc of 19 C and 20 C agree with each other within their experimental uncertainties, which might indicate a similar proton density distribution in 19 C and 20 C. The σ Z decreases monotonically without the even-odd effect as the number of removed protons increases. , X), E = 40 MeV/nucleon; measured total, fragmentation, charge-changing, charge-pickup and neutron-removal σ ; calculated σ using Glauber theory assuming halo nuclei. Liquid hydrogen target and secondary radioactive beams. Transmission method with TOMBEE spectrometer and CRYPTA target