172 research outputs found
Two neutrino double beta decay within the -approximation
We examine the contributions of odd-parity nuclear operators to the
two-neutrino double beta decay amplitude, which come from
the -wave Coulomb corrections to the electron wave functions and the recoil
corrections to the nuclear currents. Although they are formally of higher order
in or of the nucleon than the usual Fermi and Gamow-Teller
matrix elements, explicit calculations performed within the QRPA show that they
are significant when confronted with the experimental data.Comment: 9 pages, latex, no figure
Double beta decay to excited states in Nd150
The pseudo SU(3) model is used to study the double beta decay of Nd150 to the
ground and excited states of Sm150 . Low lying collective excitations of Sm150
and its BE(2) intensities are well reproduced. Expressions for the two neutrino
double beta decay to excited states are developed and used to describe the
decay of Nd150 . The existence of selection rules which strongly restrict the
decay is discussed.Comment: 22 pages, LaTeX, 1 figure with Postscript file available under
request at [email protected]
Neutrinoless Double Beta Decay in Heavy Deformed Nuclei
The zero neutrino mode of the double beta decay in heavy deformed nuclei is
investigated in the framework of the pseudo SU(3) model, which has provided an
accurate description of collective nuclear structure and predicted half-lives
for the two neutrino mode in good agreement with experiments. In the case of
the calculated zero neutrino half-life is at least three orders of
magnitude greater than the two neutrino one, giving strong support of the
identification of the radiochemically determined half-life as being the two
neutrino double beta decay. For the zero neutrino matrix elements
are of the order of magnitude of, but lesser than, those evaluated using the
QRPA. This result confirms that different nuclear models produce similar zero
neutrino matrix elements, contrary to the two neutrino case. Using these pseudo
SU(3) results and the upper limit for the neutrino mass we estimate the
half-lives for six nuclei. An upper limit for majoron
coupling constant is extracted from the experimental data.Comment: 19 pages, LaTeX, 2 figures not included, availables as poscript files
upon reques
Covariant Quantum Dynamical Semigroups: Unbounded generators
A survey of the probabilistic approaches to quantum dynamical semigroups with
unbounded generators is given. An emphasis is made upon recent advances in the
structural theory of covariant Markovian master equations. The relations with
the classical Levy-Khinchin formula are elucidated. As an example, a complete
characterizations of the Galilean covariant irreversible quantum Markovian
evolutions is given in terms of the corresponding quantum master and Langevin
equations. Important topics for future investigation are outlined.Comment: 14 pages,Latex, no figures, submitted to the Semigroup Volume, Group
21, Goslar 199
Synthesis of 5-methyl-1,2,4-triazolo[1,5- a] pyrimidin-7(4 H)-one - A semi-product of the synthesis of antiviral drug triazide® in the conditions of microwave excitation
5-Methyl-1,2,4-triazolo[1,5-a]pyrimidine-7(4H)-one was synthesized (the intermediate product for the syn-thesis of the antiviral drug Triazide®) under microwave radiation. Conversion of the starting reagents to the target product reached 95% due to experimentally selected conditions. © 2019 Author(s)
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