Radiative n 10B Capture at Thermal and Astrophysical Energies

Abstract

We have studied the neutron-capture reactions 10,11 B(n, ) and the role of the 11 B(n, ) reaction in seeding r-process nucleosynthesis. The possibility of the description of the available experimental data for cross sections of the neutron capture reaction on 10 B at thermal and astrophysical energies, taking into account the resonance at 475 keV, was considered within the framework of the modified potential cluster model (MPCM) with forbidden states and accounting for the resonance behavior of the scattering phase shifts. In the framework of the same model the possibility of describing the available experimental data for the total cross sections of the neutron radiative capture on 11 B at thermal and astrophysical energies were considered with taking into account the 21 and 430 keV resonances. Description of the available experimental data on the total cross sections and astrophysical S-factor of the radiative proton capture on 11 B to the ground state of 12 C was treated at astrophysical energies. The possibility of description of the experimental data for the astrophysical S-factor of the radiative proton capture on 14 C to the ground state of 15 N at astrophysical energies, and the radiative proton capture on 15 N at the energies from 50 to 1500 keV was considered in the framework of the MPCM with the classification of the orbital states according to Young tableaux. It was shown that, on the basis of the M1 and the E1 transitions from different states of the p 15 N scattering to the ground state of 16 O in the p 15 N channel, it is quite succeed to explain general behavior of the S-factor in the considered energy range in the presence of two resonances.PACS Number(s): 21.60. Gx, 25.20.Lj, 25.40.Lw, 26.20.Np, 26.35.+c, 26.50.+x, 26.90.+n, 98.80.Ft The measurements of the reaction rate for 11 В(р,) process at low energies, generally, are focused in the narrow resonance range at Е р = 163 keV with small width. Study of this resonance with the help of the 11 В(р, 0+1 ) reaction 8 allows one to obtain width of  = 6.7 keV and cross section of   = 125 μb in the resonance range, which differ from the assumed values 9 ( = 5.3 keV and   = 158 μb) more than by 20%. The values  = 5.4 keV and   = 130 μb were obtained relatively recently in Ref. 10, and was drawn the conclusion that this resonance plays the key role in the determination of the reaction rate for the 11 В(р,) process at low and astrophysical energies. Therefore, this reaction can play the certain role in different thermonuclear processes in the Universe at synthesis of 12 C.Recently, for example in Ref. 11, it was supposed that baryon number fluctuations in the early Universe lead to the formation of high-density proton-rich and low-density neutron-rich regions. This might be the result of the nucleosynthesis of elements with mass A  12 in the neutron-rich regions of the early Universe. 12,13 The special interest is the nucleus 14 C, 14 which is produced by successive neutron capture 1,2,3,4,5 … 12 C(n,γ) 13 C(n,γ) 14 C … .(3)The nucleus 14...

Influence of low-lying resonances on reaction rates for 10B(n,γ)11B capture

“…The values given in Table 3 as No.7-No.10 are obtained for the parameters of all other potentials without FSs of four considered ESs of 11 B in the n 10 B channel. Note that parameters of two last potentials slightly changed relatively to results of [17], therefore new data for binding energy of these states come into view [16], in comparison with [18].…”

“…1. We are using parameters, obtained in [17] and listed as No.4 in Table 3, for potentials of the nonresonance S scattering waves. They lead to zero scattering phase shifts at energies up to 1 MeV.…”

“…In subsequent results for this AC [42] the specified value equals 1.82(15) fm -1/2 is given, which after recalculation gives 1.52 (12) dimensionless form and completely matches with the value obtained here. However, the spectroscopic factor S f in the n 10 B channel does not take into account in such estimations [17]. Its values in the interval from 0.81 to 5.05, with the average of the range 2.93(2.12) are given in review work [43].…”

“…New data on spectra of 11 B from [16] are used in the present calculations as against with our previous paper [17], where results of earlier review [18] were used. In this case, as against with our previous work, we take into account resonances of three scattering phase shifts of initial particles of the input channel.…”