416 research outputs found
70Ge(p,gamma)71As and 76Ge(p,n)76As cross sections for the astrophysical p process: sensitivity of the optical proton potential at low energies
The cross sections of the 70Ge(p,gamma)71As and 76Ge(p,n)76As reactions have
been measured with the activation method in the Gamow window for the
astrophysical p process. The experiments were carried out at the Van de Graaff
and cyclotron accelerators of ATOMKI. The cross sections have been derived by
measuring the decay gamma-radiation of the reaction products. The results are
compared to the predictions of Hauser-Feshbach statistical model calculations
using the code NON-SMOKER. Good agreement between theoretical and experimental
S factors is found. Based on the new data, modifications of the optical
potential used for low-energy protons are discussed.Comment: Accepted for publication in Phys. Rev.
Precise half-life measurement of 110Sn and 109In isotopes
The half-lives of 110Sn and 109In isotopes have been measured with high
precision. The results are T1/2 =4.173 +- 0.023 h for 110Sn and T1/2 = 4.167
+-0.018 h for 109In. The precision of the half-lives has been increased by a
factor of 5 with respect to the literature values which makes results of the
recently measured 106Cd(alpha,gamma)110Sn and 106Cd(alpha,p)109In cross
sections more reliable.Comment: 3 pages, 2 figures, accepted for publication in Phys. Rev C as brief
repor
Small union with large set of centers
Let be a fixed set. By a scaled copy of around
we mean a set of the form for some .
In this survey paper we study results about the following type of problems:
How small can a set be if it contains a scaled copy of around every point
of a set of given size? We will consider the cases when is circle or sphere
centered at the origin, Cantor set in , the boundary of a square
centered at the origin, or more generally the -skeleton () of an
-dimensional cube centered at the origin or the -skeleton of a more
general polytope of .
We also study the case when we allow not only scaled copies but also scaled
and rotated copies and also the case when we allow only rotated copies
The Szemeredi-Trotter Theorem in the Complex Plane
It is shown that points and lines in the complex Euclidean plane
determine point-line incidences. This
bound is the best possible, and it generalizes the celebrated theorem by
Szemer\'edi and Trotter about point-line incidences in the real Euclidean plane
.Comment: 24 pages, 5 figures, to appear in Combinatoric
Precise half-life measurement of the 10 h isomer in 154Tb
The precise knowledge of the half-life of the reaction product is of crucial
importance for a nuclear reaction cross section measurement carried out with
the activation technique. The cross section of the 151Eu(alpha,n)154Tb reaction
has been measured recently using the activation method, however, the half-life
of the 10 h isomer in 154Tb has a relatively high uncertainty and ambiguous
values can be found in the literature. Therefore, the precise half-life of the
isomeric state has been measured and found to be 9.994 h +- 0.039 h. With
careful analysis of the systematic errors, the uncertainty of this half-life
value has been significantly reduced.Comment: Accepted for publication in Nuclear Physics
High precision Y(,)Y scattering at low energies
Elastic scattering cross sections of the Y(,)Y
reaction have been measured at energies E = 15.51 and 18.63 MeV. The
high precision data for the semi-magic nucleus Y are used to
derive a local potential and to evaluate the predictions of global and regional
-nucleus potentials. The variation of the elastic alpha scattering
cross sections along the isotonic chain is investigated by a study of
the ratios of angular distributions for Y(,)Y and
Mo(,)Mo at E 15.51 and 18.63
MeV. This ratio is a very sensitive probe at energies close to the Coulomb
barrier, where scattering data alone is usually not enough to characterize the
different potentials. Furthermore, -cluster states in Nb =
Y are investigated
Alpha-induced cross sections of 106Cd for the astrophysical p-process
The 106Cd(alpha,gamma)110Sn reaction cross section has been measured in the
energy range of the Gamow window for the astrophysical p-process scenario. The
cross sections for 106Cd(alpha,n)109Sn and for 106Cd(alpha,p)109In below the
(alpha,n) threshold have also been determined. The results are compared with
predictions of the statistical model code NON-SMOKER using different input
parameters. The comparison shows that a discrepancy for 106Cd(alpha,gamma)110Sn
when using the standard optical potentials can be removed with a different
alpha+106Cd potential. Some astrophysical implications are discussed.Comment: 10 pages, 9 figures, accepted for publication in Phys. Rev
Alpha-induced reactions for the astrophysical p-process: the case of 151Eu
The cross sections of 151Eu(alpha,gamma)155Tb and 151Eu(alpha,n)154Tb
reactions have been measured with the activation method. Some aspects of the
measurement are presented here to illustrate the requirements of experimental
techniques needed to obtain nuclear data for the astrophysical p-process
nucleosynthesis. Preliminary cross section results are also presented and
compared with the predictions of statistical model calculations.Comment: Accepted for publication in Journal of Physics Conference Series,
proceeding of the Nuclear Physics in Astrophysics IV. conferenc
Investigation of 74As decay branching ratio dependence on the host material
The branching ratio between the beta- and beta+/electron capture decay of
74As has been measured in different host materials such as Ta, Al, Ge and
mylar. No significant dependence of the branching ratio on the host material
has been observed. The half-life of 74As has also been measured in metallic Ta
and in semiconductor Ge, no difference has been found and the results are in
agreement with the literature value. The obtained results provide an upper
limit for the possible host material dependence of the decay rate in 74As.Comment: Accepted for publication in Europhysics Letter
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