Relativistic continuum-continuum coupling in the dissociation of halo nuclei

A relativistic coupled-channels theory for the calculation of dissociation cross sections of halo nuclei is developed. A comparison with non-relativistic models is done for the dissociation of $^{8}$B projectiles. It is shown that neglecting relativistic effects leads to seizable inaccuracies in the extraction of the astrophysical S-factor for the proton+beryllium radiative capture reaction.Comment: 4 pages, 2 figures, version accepted for publication at Physics Review Letter

The reaction 13C(alpha,n)16O: a background for the observation of geo-neutrinos

The absolute cross section of the $^{13}$C($\alpha$,n)$^{16}$O reaction has been measured at E$_{\alpha}$ = 0.8 to 8.0 MeV with an overall accuracy of 4%. The precision is needed to subtract reliably a background in the observation of geo-neutrinos, e.g. in the KamLAND detector.Comment: LaTex file, 13 pages including 3 ps figures. Any request to [email protected]. Phys. Rev . C, to appea

Theoretical photo-disintegration of 16^{16}O

The photodisintegration of $^{16}$O is predicted to be dominated by $E$2 excitation in the vicinity of the $\alpha$-particle threshold. The reaction rates of $^{12}$C($\alpha$,$\gamma$)$^{16}$O are expected to be determined from this reaction.Comment: 3 pages, 2 figures, Proceedings of Nuclei in the Cosmos (NIC-XIV). 19-24 June 2016, Niigata, Japa

Proton Threshold States in the 22Na(p,gamma)23Mg Reaction and Astrophysical Implications

Proton threshold states in 23Mg are important for the astrophysically relevant proton capture reaction 22Na(p,gamma)23Mg. In the indirect determination of the resonance strength of the lowest states, which were not accessible by direct methods, some of the spin-parity assignments remained experimentally uncertain. We have investigated these states with Shell Model, Coulomb displacement, and Thomas-Ehrman shift calculations. From the comparison of calculated and observed properties we relate the lowest relevant resonance state at E=7643 keV to an excited 3/2+ state in accordance with a recent experimental determination by Jenkins et al.. From this we deduce significantly improved values for the 22Na(p,gamma)23Mg reaction rate at stellar temperatures below T_9=0.1K.Comment: 8 pages, 4 figures, 6 table

Study of the 12C+12C fusion reactions near the Gamow energy

The fusion reactions 12C(12C,a)20Ne and 12C(12C,p)23Na have been studied from E = 2.10 to 4.75 MeV by gamma-ray spectroscopy using a C target with ultra-low hydrogen contamination. The deduced astrophysical S(E)* factor exhibits new resonances at E <= 3.0 MeV, in particular a strong resonance at E = 2.14 MeV, which lies at the high-energy tail of the Gamow peak. The resonance increases the present non-resonant reaction rate of the alpha channel by a factor of 5 near T = 8x10^8 K. Due to the resonance structure, extrapolation to the Gamow energy E_G = 1.5 MeV is quite uncertain. An experimental approach based on an underground accelerator placed in a salt mine in combination with a high efficiency detection setup could provide data over the full E_G energy range.Comment: 4 Pages, 4 figures, accepted for publication in Phys. Rev. Let

Notes on the Pollination of Some Liliaceae and a Few Other Plants

It will not be necessary in this connection to refer to the literature. This may be obtained from such works as Herman \u27Mueller and Darcy W. Thompson. In the identification of insects help was obtained from Prof. Osborn and Miss Beach

LUNA: Nuclear Astrophysics Deep Underground

Nuclear astrophysics strives for a comprehensive picture of the nuclear reactions responsible for synthesizing the chemical elements and for powering the stellar evolution engine. Deep underground in the Gran Sasso laboratory the cross sections of the key reactions of the proton-proton chain and of the Carbon-Nitrogen-Oxygen (CNO) cycle have been measured right down to the energies of astrophysical interest. The salient features of underground nuclear astrophysics are summarized here. The main results obtained by LUNA in the last twenty years are reviewed, and their influence on the comprehension of the properties of the neutrino, of the Sun and of the Universe itself are discussed. Future directions of underground nuclear astrophysics towards the study of helium and carbon burning and of stellar neutron sources in stars are pointed out.Comment: Invited review, submitted to Annu. Rev. Nucl. Part. Scienc

Imaginary-time method for radiative capture reaction rate

We propose a new computational method for astrophysical reaction rate of radiative capture process. In the method, an evolution of a wave function is calculated along the imaginary-time axis which is identified as the inverse temperature. It enables direct evaluation of reaction rate as a function of temperature without solving any scattering problem. The method is tested for two-body radiative capture reaction, ${^{16}{\rm O}}(\alpha,\gamma){^{20}{\rm Ne}}$, showing that it gives identical results to that calculated by the ordinary procedure. The new method will be suited for calculation of triple-alpha radiative capture rate for which an explicit construction of the scattering solution is difficult.Comment: 8 pages, 7 figure

Nuclear masses, deformations and shell effects

We show that the Liquid Drop Model is best suited to describe the masses of prolate deformed nuclei than of spherical nuclei. To this end three Liquid Drop Mass formulas are employed to describe nuclear masses of eight sets of nuclei with similar quadrupole deformations. It is shown that they are able to fit the measured masses of prolate deformed nuclei with an RMS smaller than 750 keV, while for the spherical nuclei the RMS is, in the three cases, larger than 2000 keV. The RMS of the best fit of the masses of semi-magic nuclei is also larger than 2000 keV. The parameters of the three models are studied, showing that the surface symmetry term is the one which varies the most from one group of nuclei to another. In one model, isospin dependent terms are also found to exhibit strong changes. The inclusion of shell effects allows for better fits, which continue to be better in the prolate deformed nuclei regionComment: 10 pages, 8 tables, Proc. of the XXXIV Nuclear Physics Symposium, January 4-7 2011, Cocoyoc, Morelos, Mexico. IOP Journal of Physics: Conference Series (in press

Solving the two-center nuclear shell-model problem with arbitrarily-orientated deformed potentials

A general new technique to solve the two-center problem with arbitrarily-orientated deformed realistic potentials is demonstrated, which is based on the powerful potential separable expansion method. As an example, molecular single-particle spectra for $^{12}$C + $^{12}$C $\to$ $^{24}$Mg are calculated using deformed Woods-Saxon potentials. These clearly show that non-axial symmetric configurations play a crucial role in molecular resonances observed in reaction processes for this system at low energy