Consistent optical potential for incident and emitted low-energy $\alpha$ particles. II. $\alpha$-emission in fast-neutron induced reactions on Zr isotopes

Abstract

Background: Challenging questions of the $\alpha$-particle optical-model potential (OMP) are still pointed out by recent high-precision measurements of $\alpha$-induced reaction data below the Coulomb barrier. Moreover, the reliability of a previous OMP for $\alpha$-particles on nuclei within the mass number range 45$\le$$A$$\le$209 has been recently proved for emitted $\alpha$ particles as well, but only in the case of proton-induced reactions on Zn isotopes [Phys. Rev. C {\bf 91}, 064611 (2015), Paper I]. Purpose: Analysis of most recent $(\alpha ,\gamma )$ reaction data for Ge and Zr isotopes, which provides an additional validation of the above-mentioned potential, is related to a further account of $\alpha$-particle emission in neutron-induced reactions on Zr isotopes, at the same time with a suitable description of all competitive processes. Methods: A consistent parameter set, established or validated by independent analysis of recent various data, particularly $\gamma$-ray strength functions, have been involved within model calculation of the $(\alpha ,\gamma )$ as well as $(n,\alpha )$ reaction cross sections. The latter are part of the whole analysis of the neutron activation of Zr isotopes, in order to avoid any error compensation or latent ambiguity. Results: The aforesaid potential provides a consistent description of recent $\alpha$-induced reaction data with no empirical rescaling factors of the $\gamma$ and/or nucleon widths. On the other hand, its use leads to underestimated predictions of the pre-equilibrium emission and statistical models for the $(n,\alpha )$ reaction cross sections. Conclusions: An optical potential with a volume imaginary component seems to be needed to describe the low-energy $\alpha$-particle evaporation, while only surface absorption occurs in $\alpha$-induced reactions at similar energies.

18 pages, 11 figures, accepted for publication in Phys. Rev. C

References in corpus (8)

• Further explorations of the alpha-particle optical model potential at low energies for the mass range A=45-209
• Novel technique for constraining r-process (n,$\gamma$) reaction rates
• Impact of a low-energy enhancement in the gamma-ray strength function on the radiative neutron-capture
• Spin projection in the shell model Monte Carlo method and the spin distribution of nuclear level densities
• The gamma-ray spectrometer HORUS and its applications for nuclear astrophysics
• Analysis of uncertainties in alpha-particle optical-potential assessment below the Coulomb barrier
• Alpha-particle optical potential proofs at astrophysically relevant energies
• Shell-gap reduced level densities in ${}^{89,90}$Y

Cited by in corpus (3)

• First direct measurement of ${}^{59}$Cu(p,$\alpha$)${}^{56}$Ni: A step towards constraining the Ni-Cu cycle in the Cosmos
• Role of consistent parameter sets in an assessment of the alpha-particle optical potential below the Coulomb barrier
• Optical potential for incident and emitted low-energy $\alpha$ particles. III. Non-statistical processes induced by neutrons on Zr, Nb, and Mo nuclei