Reaction dependence of nuclear decay linewidths

Abstract

Various light-and heavy-ion reactions, 20 < E i 100 MeV, have been used to study the reaction dependence of a-decay widths for *Be*(2+, 2.9 MeV) and '60*(1-, 9.6 MeV). Although slight differences (< 20 %) are found for the observed line shapes (F), the resonance widths inferred (F,) are self-consistent and indicate little if any reaction dependence (i 10 %). Near a decay threshold one may expect F < FR by 20 % or more, however, and thus care must be taken in comparing decay widths inferred from nuclear reactions with those from scattering resonances. Reduced formal a-decay widths of y: = 68Ok 100 keV (s = 4.8 fm) and 7: = 350+50 keV (S = 5.4 fm), corresponding to 19: = 0.50 and 6: = 0.49 are deduced for sBe*(2+, 2.9 MeV) and 16G*(]-, 9.6 MeV) using the nuclear-reaction Fa values and a particular set of a-nucleus potentials.

Microscopic clustering in light nuclei

“…This is the value the reduced width should adopt if the α-particles are fully preformed. For this particular state, it is found that the experimental width is very close to the Wigner limit, again indicating the existence of the cluster structure (Cerny, 1974;Overway et al, 1981). A further signature, not available to the decay of the example states in 8 Be, is the measurement of the dominant decay channel.…”

Discovery of a New Broad Resonance inNe19: Implications for the Destruction of the Cosmicγ-Ray EmitterDalouzy1, Achouri2, Aliotta3 et al. 2009Phys. Rev. Lett.

“…(Dated: February 4, 2009) Six proton-emitting states in 19 N e were studied through the inelastic scattering reaction H( 19 N e, p) 19 N e * (p) 18 F . Their energies and widths were derived from the protons detected at zero degree, while proton-proton angular correlations between the detector at zero degree and a segmented annular detector were used to determine their spin value.…”

“…It would follow that the importance of the interference contribution between the + resonances would be much reduced. In the present paper, we report the results of a new approach developed to study excited states in 19 N e through the reaction 1 H( 19 N e, p) 19 N e * (p) 18 F . Implications to the 18 F (p, α) 15 O rate in novae are subsequently discussed.…”

“…The measured signal of the catcher was normalized to the one of a Faraday cup to provide an absolute determination of the integrated beam current. With an upper limit of 1%, no contamination of the beam by 19 19 N e * reaction, with the associated proton detected at zero degree, is presented as a function of the 19 N e * excitation energy (lower axis) and the measured energy in the laboratory (upper axis) corrected for energy losses in the beam catcher. This figure is conditioned with the detection of another proton in CD-PAD coming from the emission channel 19 N e * (p) 18 F .…”

“…The excitation energies in 19 N e produced by inelastic scattering were derived from the proton energies detected at zero degree. Above the proton emission threshold the requirement of another proton detected in CD-PAD (from 19 N e * (p) 18 F ) was used to suppress the background induced by reactions of the beam in the catcher.…”