Measurement of the Cascade Transition via the First Excited State ofO16in theC12

C. Matei

¹

,

L. Buchmann

²

,

Wolf-Rüdiger Hannes

³

et al.

Abstract

Radiative alpha-particle capture into the first excited, J(pi)=0+ state of 16O at 6.049 MeV excitation energy has rarely been discussed as contributing to the 12C(alpha,gamma)16O reaction cross section due to experimental difficulties in observing this transition. We report here measurements of this radiative capture in 12C(alpha,gamma)16O for center-of-mass energies of E=2.22 MeV to 5.42 MeV at the DRAGON recoil separator. To determine cross sections, the acceptance of the recoil separator has been simulated in GEANT as well as measured directly. The transition strength between resonances has been identified in R-matrix fits as resulting both from E2 contributions as well as E1 radiative capture. Details of the extrapolation of the total cross section to low energies are then discussed [S6.0(300)=25(-15)(+16) keV b] showing that this transition is likely the most important cascade contribution for 12C(alpha,gamma)16O.

The C12(α,γ)O16deBoer1, Görres2, Wiescher3 et al. 2017Rev. Mod. Phys.19081431View full textAdd to dashboardCite

“…The sub-Coulomb transfer reaction experiment of Avila et al (2015) has reconfirmed the earlier measurements of the α ANCs for the levels at E x = 6.92 (2 + ) and 7.12 (1 − ) MeV and has additionally measured those of the E x = 6.05 (0 + ) and 6.13 (3 − ) MeV states for the first time. These measurements reconfirmed the assertion of Schürmann et al (2011) that the large value for the low energy S-factor of the E x = 6.05 MeV transition given in Matei et al (2006) was incorrect. However, the value found in Avila et al (2015) is also in disagreement with that of Schürmann et al (2011) since their assumed ANC was significantly smaller than that measured by Avila et al (2015).…”

“…Further, in that work an R-matrix fit was made to this data that gave a much larger low energy contribution than previously estimated. A subsequent measurement by Schürmann et al (2011) over a more limited higher energy range claimed that their data was inconsistent with that of Matei et al (2006) and their R-matrix fit predicted the opposite extreme, that the transition's contribution was lower than previously estimated. A reanalysis of the data of Schürmann et al (2011) by deBoer et al (2013 found a value in between the two, which was closer to previous estimates.…”

“…The few that are excluded are the ground state capture data of and , both the ground state and cascade capture data of Kettner et al (1982), the E2 data of Redder et al (1987), and the E x = 6.05 MeV transition data of Matei et al (2006). Further, the β delayed α data sets of France III et al (2007) and Neubeck et al (1974), that is the Yale, Mainz, and Seattle data, are also excluded because not enough information regarding the target effect corrections have been given to perform a reanalysis of these data sets.…”

“…Cascade transition excitation curves for the 12 C(α, γ) 16 O reaction have been measured by Kettner et al (1982); Matei et al (2006); Redder et al (1987);and Schürmann et al (2011). The measurement of these transitions are complicated experimentally by the close energy spacing of the bound states at E x = 6.05 (0 + ) and 6.13 (3 − ) MeV and those at E x = 6.92 (2 + ) and 7.12 (1 − ) MeV.…”

“…The measurement of Matei et al (2006) reports an excitation curve for this transition over a wide energy range. Further, in that work an R-matrix fit was made to this data that gave a much larger low energy contribution than previously estimated.…”