511 research outputs found
Investigation of the Earth Ionosphere using the Radio Emission of Pulsars
The investigation of the Earth ionosphere both in a quiet and a disturbed
states is still desirable. Despite recent progress in its modeling and in
estimating the electron concentration along the line of sight by GPS signals,
the impact of the disturbed ionosphere and magnetic field on the wave
propagation still remains not sufficiently understood. This is due to lack of
information on the polarization of GPS signals, and due to poorly conditioned
models of the ionosphere at high altitudes and strong perturbations. In this
article we consider a possibility of using the data of pulsar radio emission,
along with the traditional GPS system data, for the vertical and oblique
sounding of the ionosphere. This approach also allows to monitor parameters of
the propagation medium, such as the dispersion measure and the rotation measure
using changes of the polarization between pulses. By using a selected pulsar
constellation it is possible to increase the number of directions in which
parameters of the ionosphere and the magnetic field can be estimated.Comment: 13 pages, 4 figures, Baltic Astronomy, vol.22, 53-65, 201
Transition from direct to sequential two-proton decay in - shell nuclei
Transitions among different mechanisms of two-proton decay are studied in
general. The introduced improved direct-decay model generalizes the
semi-analytical models used before and provides flawless phenomenological
description of three-body correlations in decays. This is demonstrated by
examples of the low-lying Ne state decays. Different forms of transition
dynamic are shown to be highly probable beyond the proton dripline for the
- shell nuclei. It is demonstrated that transition dynamic of
emitters can provide means for extraction of a width of the ground-state
resonance of a core+ subsystem of the core+ system. Practical
applicability of the method is demonstrated by properties of the F
ground state derived from the ^{15}\mbox{Ne}\rightarrow
^{\,13\!\!}\mbox{O}+2p decay data and of the Cl ground state derived
from the ^{30}\mbox{Ar}\rightarrow ^{\,28\!\!}\mbox{S}+2p decay data.Comment: 8 pages, 10 figure
Lifetime and fragment correlations for the two-neutron decay of O ground state
The structure and decay of O are investigated in a three-body
O+ model suitable for studies of the long-lived (including
radioactivity timescale) states. We have found extremely strong effect of the
subbarrier configuration mixing on the decay width of true emitters due to
core recoil and neutron-neutron final state interaction. This effect is far
exceeding analogous effect in the true emitters. Our calculations provide
reasonably narrow boundaries for the lifetime vs.\ decay energy dependence for
the true emission. An upper limit of keV for the decay energy of
the unbound O is inferred based on the recent experimental lifetime
value.Comment: 6 pages, 4 figure
Deep excursion beyond the proton dripline. II. Towards the limits of nuclear structure existence
Prospects of experimental studies of argon and chlorine isotopes located far beyond the proton dripline are studied by using systematics and cluster models. The deviations from the widespread systematics observed in
28
,
29
Cl
and
29
,
30
Ar
have been theoretically substantiated, and analogous deviations have been predicted for the lighter chlorine and argon isotopes. The limits of nuclear structure existence are predicted for Ar and Cl isotopic chains, with
26
Ar
and
25
Cl
found to be the lightest sufficiently long-living nuclear systems. By simultaneous measurements of protons and
γ
rays following decays of such systems as well as their
β
-delayed emission, an interesting synergy effect may be achieved, which is demonstrated by the example of
30
Cl
and
31
Ar
ground-state studies. Such a synergy effect may be provided by the new EXPERT setup (EXotic Particle Emission and Radioactivity by Tracking) being operated inside the fragment separator and spectrometer facility at GSI, Darmstadt.This work was supported in part by the Hessian Ministry for Science and Art (HMWK) through the LOEWE funding scheme Helmholtz International Center for FAIR (HIC for FAIR); the Helmholtz Association (Grant No. IK-RU-002); the Russian Science Foundation (Grant No. 17-12-01367); the Polish National Science Center (Contract No. UMO-2015/17/B/ST2/00581); the Polish Ministry of Science and Higher Education (Grant No. 0079/DIA/2014/43, Grant Diamentowy); the Helmholtz-CAS Joint Research Group (Grant No. HCJRG-108); the Ministry of Education & Science, Spain (Contract No. FPA2016-77689-C2-1-R); the Ministry of Education, Youth and Sports, Czech Republic (Projects No. LTT17003 and No. LM2015049); and the Justus-Liebig-Universitat Giessen (JLU) and the GSI under the JLU-GSI strategic Helmholtz partnership agreement. This work was carried out in the framework of the Super-FRS Experiment collaboration. This article is a part of the Ph.D. thesis of D. Kostyleva
Deep excursion beyond the proton dripline. I. Argon and chlorine isotope chains
The proton-unbound argon and chlorine isotopes have been studied by measuring trajectories
of their decay-in-flight products by using a tracking technique with micro-strip detectors. The
proton (1p) and two-proton (2p) emission processes have been detected in the measured angular
correlations “heavy-fragment”+p and “heavy-fragment”+p+p, respectively. The ground states of
the previously unknown isotopes 30Cl and 28Cl have been observed for the first time, providing the
1p separation energies Sp of −0.48(2) and −1.60(8) MeV, respectively. The relevant systematics of
1p and 2p separation energies have been studied theoretically in the core+p and core+p+p cluster
models. The first-time observed excited states of 31Ar allow to infer the 2p-separation energy S2p
of 6(34) keV for its ground state. The first-time observed state in 29Ar with S2p = −5.50(18) MeV
can be identified either as a ground or an excited state according to different systematics.This work was supported in part by the Helmholtz International Center for FAIR (HIC for FAIR); the Helmholtz Association (Grant No. IK-RU-002); the Russian Science Foundation (Grant No. 17-12-01367); the Polish National Science Center (Contract No. UMO-2015/17/B/ST2/00581); the Polish Ministry of Science and Higher Education (Grant No. 0079/DIA/2014/43, Grant Diamentowy); the Helmholtz-CAS Joint Research Group (Grant No. HCJRG-108); the Ministry of Education & Science, Spain (Contract No. FPA2016-77689-C2-1-R); the Hessian Ministry for Science and Art (HMWK) through the LOEWE funding scheme Helmholtz International Center for FAIR (HIC for FAIR); the Justus-Liebig-Universitat Giessen (JLU) and the GSI under the JLU-GSI strategic Helmholtz partnership agreement. This work was carried out in the framework of the Super-FRS Experiment collaboration. This article is a part of the Ph.D. thesis of D. Kostyleva
High-precision measurement of the half-life of Ga
The beta-decay half-life of 62Ga has been studied with high precision using
on-line mass separated samples. The decay of 62Ga which is dominated by a 0+ to
0+ transition to the ground state of 62Zn yields a half-life of T_{1/2} =
116.19(4) ms. This result is more precise than any previous measurement by
about a factor of four or more. The present value is in agreement with older
literature values, but slightly disagrees with a recent measurement. We
determine an error weighted average value of all experimental half-lives of
116.18(4) ms.Comment: 9 pages, 5 figures, accepted for publication in PR
Breakdown of the Z=8 shell closure in unbound 12O and its mirror symmetry
An excited state in the proton-rich unbound nucleus 12O was identified at 1.8(4) MeV via missing-mass spectroscopy with the 14O(p,t) reaction at 51 AMeV. The spin-parity of the state was determined to be 0+ or 2+ by comparing the measured differential cross sections with distorted-wave calculations. The lowered location of the excited state in 12O indicates the breakdown of the major shell closure at Z=8 near the proton drip line. This demonstrates the persistence of mirror symmetry in the disappearance of the magic number 8 between 12O and its mirror partner 12Be
Deep excursion beyond the proton dripline. I. Argon and chlorine isotope chains
The proton-unbound argon and chlorine isotopes have been studied by measuring trajectories
of their decay-in-flight products by using a tracking technique with micro-strip detectors. The
proton (1p) and two-proton (2p) emission processes have been detected in the measured angular
correlations “heavy-fragment”+p and “heavy-fragment”+p+p, respectively. The ground states of
the previously unknown isotopes 30Cl and 28Cl have been observed for the first time, providing the
1p separation energies Sp of −0.48(2) and −1.60(8) MeV, respectively. The relevant systematics of
1p and 2p separation energies have been studied theoretically in the core+p and core+p+p cluster
models. The first-time observed excited states of 31Ar allow to infer the 2p-separation energy S2p
of 6(34) keV for its ground state. The first-time observed state in 29Ar with S2p = −5.50(18) MeV
can be identified either as a ground or an excited state according to different systematics.Helmholtz Association grant IK-RU-002Helmholtz International Center for FAIR HIC for FAIRRussian Science Foundation grant No. 17-12-01367Polish National Science Center Contract No. UMO- 2015/17/B/ST2/00581Polish Ministry of Science and Higher Education Grant No. 0079/DIA/2014/43, Grant DiamentowyHelmholtz- CAS Joint Research Group grant HCJRG-10
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