6,827 research outputs found
A new method of alpha ray measurement using a Quadrupole Mass Spectrometer
We propose a new method of alpha()-ray measurement that detects
helium atoms with a Quadrupole Mass Spectrometer(QMS). A demonstration is
undertaken with a plastic-covered Am -emitting source to detect
-rays stopped in the capsule. We successfully detect helium atoms that
diffuse out of the capsule by accumulating them for one to 20 hours in a closed
chamber. The detected amount is found to be proportional to the accumulation
time. Our method is applicable to probe -emitting radioactivity in bulk
material.Comment: 8 pages, 6 figure
Ingredients of nuclear matrix element for two-neutrino double-beta decay of 48Ca
Large-scale shell model calculations including two major shells are carried
out, and the ingredients of nuclear matrix element for two-neutrino double beta
decay are investigated. Based on the comparison between the shell model
calculations accounting only for one major shell (-shell) and those for two
major shells (-shell), the effect due to the excitation across the two
major shells is quantitatively evaluated.Comment: To appear in J. Phys. Soc. Conf. Proc. (ARIS2014); for ver.2, Fig.1
is revise
Effect of Spin-Dependent Short-Range Correlations on Nuclear Matrix Elements for Neutrinoless Double Beta Decay of Ca
The neutrinoless double beta decay is a pivotal weak nuclear process that
holds the potential to unveil the Majorana nature of neutrinos and predict
their absolute masses. In this study, we delve into examining the impact of
spin-dependent short-range correlations (SRC) on the nuclear matrix elements
(NMEs) for the light neutrino-exchange mechanism in neutrinoless double beta
() decay of Ca, employing an extensive interacting
nuclear shell model. All computations are performed employing the effective
shell model Hamiltonian GXPF1A, encompassing the entire model space
through the closure approximation. Our investigation examines the NMEs'
dependencies on factors such as the number of intermediate states, coupled
spin-parity attributes of neutrons and protons, neutrino momentum,
inter-nucleon separation, and closure energy. This scrutiny is performed with
respect to both the conventional Jastrow-type approach of SRC, employing
various parameterizations, and the spin-dependent SRC paradigm. Our findings
illuminate a discernible distinction in NMEs induced by spin-dependent SRC,
differing by approximately 10-20\% from those computed through the conventional
Jastrow-type SRC, incorporating distinct parameterizations.Comment: 13 pages, 5 figures, submitted in the journal Universe, MDP
Nonadiabatic generation of coherent phonons
The time-dependent density functional theory (TDDFT) is the leading
computationally feasible theory to treat excitations by strong electromagnetic
fields. Here the theory is applied to coherent optical phonon generation
produced by intense laser pulses. We examine the process in the crystalline
semimetal antimony (Sb), where nonadiabatic coupling is very important. This
material is of particular interest because it exhibits strong phonon coupling
and optical phonons of different symmetries can be observed. The TDDFT is able
to account for a number of qualitative features of the observed coherent
phonons, despite its unsatisfactory performance on reproducing the observed
dielectric functions of Sb. A simple dielectric model for nonadiabatic coherent
phonon generation is also examined and compared with the TDDFT calculations.Comment: 19 pages, 11 figures. This is prepared for a special issue of Journal
of Chemical Physics on the topic of nonadiabatic processe
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