Dipole strength inY89up to the neutron-separation energy

Abstract

Photoexcitation of the N = 50 nucleus 89 Y has been performed at the bremsstrahlung facility at the superconducting electron accelerator ELBE at electron energies of E kin e = 9.5 and 13.2 MeV. About 250 levels up to the neutron-separation energy were identified. Statistical methods were applied to estimate intensities of inelastic transitions and to correct the intensities of the ground-state transitions for their branching ratios. The photoabsorption cross section derived in this way up to the neutron-separation energy is combined with the photoabsorption cross section obtained from (γ, n) data and provides information about the extension of the giant dipole resonance toward energies below the neutron-separation energy. An enhancement of E1 strength has been found in the range from about 6 to 11 MeV. The experimental photoabsorption cross sections of 89 Y and of the neighboring N = 50 isotones 88 Sr and 90 Zr are compared with predictions of the quasiparticle-random-phase approximation.

Dipole strength inSe80forsprocess and nuclear transmutation ofSe79

“…The efficiency values deduced from these measurements agreed with the simulated values within their uncertainties [45]. Similar results were obtained for the resonances at 4.44 and 11.66 MeV in 12 C populated in the 11 B(p,γ ) reaction at the Triangle Universities Nuclear Laboratory (TUNL) Van-de-Graaff accelerator [46].…”

“…We applied statistical methods to estimate the (6) 45 (10) 044304-5 intensities of branching transitions to low-lying excited levels and of the branching ratios of the ground-state transitions. These methods were also applied in earlier photon-scattering experiments at γ ELBE [11][12][13][14][15]17,18]. The intensity distribution contains ground-state transitions and, in addition, branching transitions to lower-lying excited states (inelastic transitions) as well as transitions from those states to the ground state (cascade transitions).…”

“…The low-energy tail of the GDR below S n is of particular interest because of an extra enhancement of observed E1 strength. This pygmy dipole resonance (PDR) [7][8][9], has been found, for example, in 76 Se [10], 78 Se [11], nuclides around N = 50 [12][13][14], around N = 82 [15][16][17][18], and in 181 Ta [19].…”

Compound-nuclear reactions with unstable nuclei: Constraining theory through innovative experimental approaches

“…These were subsequently employed to calculate the (n,γ) cross section of interest. Alternatively, it is possible to measure the γ-ray strength function, an important ingredient for neutron-capture calculations, in photon-scattering experiments [22][23][24]. This approach makes it possible to determine the strength function below the particle emission threshold directly, without the need to model the reaction mechanism.…”

“…Inelastic scattering and photo-neutron reactions can be used to populate a nucleus of interest across a wide range of excitation energies, up to and beyond the neutron separation energy. Bremsstrahlung photons as well as quasi-monoenergetic γ-ray beams have been used for this purpose [21][22][23][24][25][26][27][28][29]. In a few experiments, neutrons emitted from the CN were detected and the (γ,n) cross sections were determined.…”