Photoneutron emission cross sections for ${}^{13}\mathrm{C}$

Photoneutron emission cross sections were measured for ${}^{13}\mathrm{C}$ below $2n$ threshold using quasimonochromatic $\gamma$-ray beams produced in laser Compton scattering at the NewSUBARU synchrotron radiation facility. The data show fine structures in the low-energy tail of the giant-dipole resonance; the integrated strength of the fine structure below 18 MeV is intermediate among the past measurements with bremsstrahlung and the positron annihilation $\gamma$ rays. We compare the photoneutron emission data with the talys statistical model calculation implemented with the simple modified Lorentzian model of $E1$ and $M1$ strengths. We also compare the total photoabsorption cross sections for ${}^{13}\mathrm{C}$ with shell model and antisymmetrized molecular dynamics calculations as well as the statistical model calculation. We further investigate the consistency between the present photoneutron emission and the reverse ${}^{12}\mathrm{C}(n,\gamma$) cross sections through their corresponding astrophysical rate.

Figure 1

The incident $\gamma$-ray beams. The profiles have been normalized and the energy bins are 10 keV.

Figure 2

Unfolded cross sections and experimental monochromatic cross sections measured per incident LCS $\gamma$-ray beam, ${\sigma }_{\exp }^{E_{\max }}$ (black dots).

Figure 3

Photoneutron emission cross sections, $\sigma (\gamma ,1nX)$, for ${}^{13}\mathrm{C}$ (red filled circles). The bremsstrahlung data of [12] and [13] are shown by blue filled squares and open green squares, respectively. The data obtained with the positron annihilation $\gamma$ rays [14] are shown by black filled circles.

Figure 4

Comparison of the present total photoabsorption cross section with the total photoabsorption of [18]. Photoneutron emission cross sections [12, 14] used in the estimate of the photoabsorption are also shown. The blue solid line corresponds to the SMLO prediction [37].

Figure 5

Comparison of the present experimental photoneutron emission cross section (red dots) and the photoproton emission cross section of [17] with talys calculations based on the SMLO $E1$ and $M1$ strength functions.

Figure 6

(a) Results of the shell model calculation (blue) and AMD calculation (red) after smoothing with $2\gamma =1$ MeV in comparison with the total photoabsorption cross section recommended. An energy shift by - 1.5 MeV is introduced to the AMD calculation. (b) Distribution of E1 excitations in the shell model calculation with 300 Lanczos iterations. (c) Distribution of E1 excitations in the AMD calculation with an energy shift by -1.5 MeV.

Figure 7

(a) Experimental ${}^{12}\mathrm{C}(n,\gamma ){}^{13}\mathrm{C}$ Maxwellian-averaged cross sections [47, 48, 49] as a function of the temperature $T$. (b) Comparison between the ${}^{13}\mathrm{C}(\gamma ,n){}^{12}\mathrm{C}$ rates deduced from the inverse experimental cross sections of Refs. [48, 49] shown in (a) and the Planck-averaged rate estimated from the present experimental photoneutron emission of ${}^{13}\mathrm{C}$.