Annual modulation of γ rays from (α,γ) reactions induced by the α activity of radon and its daughters was reported by Tiwari, Zhang, Mei, and Cushman (TZMC). While Mohr does not contest the measurements themselves, he has commented that unrealistic (α,γ) cross sections were used in the analysis of the γ-ray flux, and thus the γ-ray fluxes calculated by TZMC are not reliable. We demonstrate that the (α,γ) cross sections obtained from talys include the energy-broadened cross sections for discrete states in the high-energy tail of the spectra, which are required in order to compare with the angle-integrated and double-differential spectra obtained from a liquid scintillator detector with an energy resolution of only ≈15%. A comparison with varying "elwidth" shows that cross sections indeed are reliable within the energy region (4 to 10 MeV) reported by TZMC, especially for the dominant contribution, which is the aluminum wall of the detector. Any differences in the (α,γ) cross sections for O16 at the level detailed by Mohr will have negligible effect on the final flux.
Bibliographical noteFunding Information:
This work was supported in part by NSF Grants No. PHY-0919278, No. PHY-1242640, No. OIA 1434142, and No. OISE 1743790, DOE Grant No. DE-SC0004768, and a Governor's Research Center Program supported by the state of South Dakota.
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