Papers by Dorel Bucurescu
Nuclear Instruments and Methods, 1979
ABSTRACT The use of a position-sensitive detector for measuring quasi-continous angular distribut... more ABSTRACT The use of a position-sensitive detector for measuring quasi-continous angular distributions is described. Examples of applications of this technique to studies of alpha-particle elastic and inelastic scattering are given.
Nuclear Physics A, 1996
The band structures of the doubly odd '"Pr nucleus has been investigated via the '19Sn( 19F,4n) '... more The band structures of the doubly odd '"Pr nucleus has been investigated via the '19Sn( 19F,4n) 'j4Pr and "'Pd( "Si,p3n) lWPr reactions at beam energies of 87 and 130 MeV, respectively. The three previously known rotational bands based on the 7r[541]3/2-(a=?~l/2)@~[514]9/2-and ~[413]5/2+@~[514]9/2-configurations have been extended to higher spins. The difference of M 2ti in the experimental alignment of the bands based on the signature partners of the [ 541]3/2-h11j2 proton orbital is discussed in terms of shape coexistence and coupling with the y-phonon but no consistent interpretation can be found. A new band consisting of quadrupole transitions has also been identified and linked unambiguously to the low-lying levels of the yrast band. Total routhian surface and cranked shell model calculations suggest a ( rrhll/:! )3&W [ 530 ] l/2-configuration for this band. The experimental ratios of reduced transition probabilities B(M1) lB(E2) of the various rotational structures are compared to the theoretical values obtained from a semiclassical model and from the two-particle plus triaxial-rotor model. Nuclear reactions '19Sn( 19F,4n), E = 87 MeV, 110Pd(2sSi,p3n), E = 130 MeV, measured E,, I,, DC0 ratios, W-coincidence, y-multiplicity. 134Pr deduced levels, J, ?r, y-branching, B(A) ratios, experimental routbians, aligned angular momenta. Enriched targets, HPGe detectors, BGO suppression shields, 4?r-BGO ball. Total routhian surface calculations, comparison with cranked shell model, semiclassical model and two-particle plus triaxial-rotor calculations.
Nuclear Physics News, 2007
Physical review letters, Jan 17, 2001
Gamma rays from the N = Z-2 nucleus (50)Fe have been observed, establishing the rotational ground... more Gamma rays from the N = Z-2 nucleus (50)Fe have been observed, establishing the rotational ground state band up to the state J(pi) = 11+ at 6.994 MeV excitation energy. The experimental Coulomb energy differences, obtained by comparison with the isobaric analog states in its mirror (50)Cr, confirm the qualitative interpretation of the backbending patterns in terms of successive alignments of proton and neutron pairs. A quantitative agreement with experiment has been achieved by exact shell model calculations, incorporating the differences in radii along the yrast bands, and properly renormalizing the Coulomb matrix elements in the pf model space.
International Journal of Modern Physics E, 2008
We present a new study of the low-lying states in 124 Te nucleus by γ-ray spectroscopy following ... more We present a new study of the low-lying states in 124 Te nucleus by γ-ray spectroscopy following 124 I β + /ε decay. The β radioactive sources were produced in the 124 Te(p, n) 124 I reaction induced by 11 MeV protons, delivered by the Bucharest FN Tandem Accelerator. The γ-rays were measured in a low background area with three large volume HPGe detectors. A total number of 276 milion double coincidence events were recorded in a six-day run. Most of the gamma line intensities previously measured were confirmed with improved accuracy and several gamma lines were obtained for the first time. Our results, combined with those from a recent (n, γ) study are compared with the predictions of the E(5) critical point symmetry model and numerical IBA-1 model calculations at the critical point of the U(5)-O(6) phase transition.
the low-lying level scheme of the odd-odd nucleus ~ 500 132pr has been investigated for the first... more the low-lying level scheme of the odd-odd nucleus ~ 500 132pr has been investigated for the first time . The radioactive z
The cross sections of the 147 Sm(p,γ) 148 Eu and 149 Sm(p,γ) 150 Eu reactions have been measured ... more The cross sections of the 147 Sm(p,γ) 148 Eu and 149 Sm(p,γ) 150 Eu reactions have been measured with the activation method, in the Gamow window for the astrophysical p process. The experiments were carried out at the IFIN-HH Tandem accelerator. The cross sections have been derived by measuring the decay γ radiations of the reaction products. The results are compared with the predictions of the Hauser -Feshbach statistical model calculations performed with the code NON-SMOKER.
For several years, in the frame of an international colaboration we have started a program to stu... more For several years, in the frame of an international colaboration we have started a program to study exotic decays at the proton drip-line with special attention to proton radioactivity in the light rare earth region. The theoretical calculations stressed the fact that p- emitting nuclei with 54 < Z < 64 are expected to be very deformed in their ground state and for this reason their study is an important test for the theoretical models that describe proton radioactivity. The decay by proton emission of the 117La nucleus has been studied via the 310 MeV 58Ni + 64Zn reaction. For this nucleus two levels that decay to the ground state of 116Ba with Ep = 783(6) keV (T1/2 = 22 (5) ms) and Ep = 933(10) keV (T1/2 = 10(5) ms ) have been discovered. Calculations performed for a deformed proton emitter reproduce quite well the experimental results confirming that 117La is strongly deformed. A search for proton radioactivity of 123Pr using a 58Ni beam (260-300 MeV) and 70Ge target has been done. The same setup for measuring the p-decay of 117La and 123Pr was used to investigate a possible decay via proton emission of the odd-odd nucleus 126Pm. We performed analysis of the deformed proton emitter 57 ≤ Z ≤ 69 by using Möller et al. and Relativistic Hartree - Bogoliubov models concerning the location of proton drip-line, the separation energies for proton separation and ground-state quadrupole deformations.
A general overview is given on the phenomenological methods used to describe the level densities ... more A general overview is given on the phenomenological methods used to describe the level densities in nuclei. Two well-known two-parameter formulas of level densities, the Back-Shifted Fermi Gas (BSFG) model and the Constant Temperature (CT) model, were used. A common ingredient of both is the spin distribution function, which contains in Ericsons's parametrization the spin-cutoff parameter σ. A realistic description of the parameters of both spin distribution function and the two level density models has been obtained by fitting the experimental data of 310 nuclei between 18 F and 251 Cf, consisting of the complete level schemes at low excitation energies and the s-wave neutron resonance spacings at the neutron binding energy. We determine a simple formula for the spin-cutoff parameter as a function of mass number and excitation energy. Also, an even-odd spin staggering in the spin distribution of the even-even nuclei was observed, and described with a simple formula. Using this newly defined spin distribution function, an empirical set of parameters of the BSFG and CT models was determined by fitting both the low-energy levels and the neutron resonance spacings. For these parameters, simple formulas were proposed that involve only quantities available from the mass tables, and allow reasonable estimations of the level density parameters for nuclei far from stability. Both the BSFG and CT models describe equally well the level densities at energies up to at least the neutron binding energy. Finally, we discuss recent experimental evidence that the CT model is the more correct description of the nuclei in the low-excitation energy (pairing) regime.
The decay of on-line mass separated 83Zr and SSZr sources has been studied by singles and coincid... more The decay of on-line mass separated 83Zr and SSZr sources has been studied by singles and coincident X-ray and ):-ray and conversion electron measurements. The previous level scheme of 83y is confirmed and 5 new levels have been added up to 2.74 MeV excitation. A decay scheme of 8~Zr with 40 levels up to 2.66 MeV in 8sy is deduced. The experimental observation below 2 MeV excitation in 85y agrees qualitatively with the predictions of the interacting boson-fermion model.
The Doppler shift attenuation method was used to determine lifetimes in the picosecond region for... more The Doppler shift attenuation method was used to determine lifetimes in the picosecond region for excited states of 117 Sb populated with the (␣,2n␥) reaction at E ␣ ϭ27.2 MeV. Interacting boson-fermion model calculations explain reasonably well the main features of the positive parity levels known up to about 2.5 MeV excitation. The mixing of the lowest one-quasiparticle 9/2 ϩ state with the intruder (2p-1h) 9/2 ϩ state, as well as the quadrupole deformation of the intruder band are also discussed. ͓S0556-2813͑98͒03809-6͔
ABSTRACT The lifetimes of twelve low spin excited states in 73As, below 2 MeV excitation, have be... more ABSTRACT The lifetimes of twelve low spin excited states in 73As, below 2 MeV excitation, have been measured with the DSA method in the 73Ge(p,nγ) reaction. The existing data (energy levels, electromagnetic moments, transition probabilities and branching ratios, one-nucleon transfer spectroscopic factors) are discussed in the frame of multi-shell interacting boson-fermion model calculations. A good agreement is obtained for a large number of levels.
The first identification of gamma-rays from excited states of the 85Mo and 88Ru nuclei is reporte... more The first identification of gamma-rays from excited states of the 85Mo and 88Ru nuclei is reported, together with a short discussion of the evolution of the nuclear structure along the N = Z and the N = 43, 44 lines.
High-spin states in the 97 Tc nucleus have been studied by in-beam γ-ray spectroscopy with the re... more High-spin states in the 97 Tc nucleus have been studied by in-beam γ-ray spectroscopy with the reaction 82 Se( 19 F,4nγ) at 68 MeV incident energy. Excited states have been observed up to about 8 MeV excitation and spin 43/2h. The observed level scheme is compared with results of shell model calculations. PACS. 21.10.Pc Single-particle levels and strength functions -23.20.Lv Gamma transitions and level energies -27.60.+j 90 ≤ A ≤ 149
Uploads
Papers by Dorel Bucurescu