Breakup effects on alpha spectroscopic factors of¹⁶O

Abstract

The triton angular distribution for the 12C(7Li,t)16O* reaction is measured at 20 MeV, populating discrete states of 16O. Continuum discretized coupled reaction channel calculations are used to to extract the alpha spectroscopic properties of 16O states instead of the distorted wave born approximation theory to include the effects of breakup on the transfer process. The alpha reduced width, spectroscopic factors and the asymptotic normalization constant (ANC) of 16O states are extracted. The error in the spectroscopic factor is about 35% and in that of the ANC about 27%.

Constraining the External Capture to the O16 Ground State and the E2 Shen1, deBoer2, Li3 et al. 2020Phys. Rev. Lett.

“…The contribution from the CN process is found to be small (less than 3% on the GS ANC [29]. The previous measurements 199 [15,16] presented the transfer reaction angular distribu-…”

“…This is about five orders of magni-41 tude below the sensitivity achieved by the most advanced is substantially larger than those determined by the precise sub-Coulomb transfer reactions [12,13]. Currently, reported experimental values of the GS ANC range from 13.9 ± 2.4 fm −1/2 to 3390 fm −1/2 [11,[14][15][16]. In light of this large discrepancy between GS ANC values and the consistent values for the 2 + ANC determined through sub-Coulomb transfer reactions, a value of 58 fm −1/2 for the GS ANC was adopted in that work [3].…”

“…[37], Oulebsir et al [38] and Adhikari et al [15], where larger uncertainties are reported. Further, at very low energies, there is a substantial enhancement to the E2 S-factor, rising to a value of 70 ± 7 keV b at 300 keV compared to the value of 45 keV b found in deBoer et al…”

An indirect technique in nuclear astrophysics: alpha-cluster transfer reaction

“…To date the ANC of the 16 O GS has been extensively investigated. There is a large discrepancy of up to a factor 240 between these reported experimental values of the GS ANC ranging from 13.9 ± 2.4 fm −1/2 to 3390 fm −1/2 [11][12][13][14][15]. Although the most recent measurement by Shen et al [15] gives a more precise value, further highprecision measurements of the 16 O GS ANC are still desirable.…”

New Determination of the 12C(α, γ)16O Reaction Rate and Its Impact on the Black-hole Mass Gap

“…Therefore, precise measurement of the GS ANC is crucial for determination of the 12 C(α, γ) 16 O reaction rate. Currently, the reported experimental GS ANC values range from 13.9 ± 2.4 to 3390 fm −1/2 (Adhikari & Basu 2009;Morais & Lichtenthäler 2011;Sayre et al 2012;Adhikari et al 2017). These values were derived from different methods including the 16 O breakup (Adhikari & Basu 2009), the elastic transfer reaction 12 C( 16 O, 12 C) 16 O (Morais & Lichtenthäler 2011), the 12 C( 7 Li, t) 16 O reaction (Adhikari et al 2017), and the R-matrix fitting (Sayre et al 2012).…”