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 ss-dd 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 $2p$ decays. This is demonstrated by examples of the low-lying $^{16}$Ne state decays. Different forms of transition dynamic are shown to be highly probable beyond the proton dripline for the $s$-$d$ shell nuclei. It is demonstrated that transition dynamic of $2p$ emitters can provide means for extraction of a width of the ground-state resonance of a core+$p$ subsystem of the core+$2p$ system. Practical applicability of the method is demonstrated by properties of the $^{14}$F ground state derived from the ^{15}\mbox{Ne}\rightarrow ^{\,13\!\!}\mbox{O}+2p decay data and of the $^{29}$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 26^{26}O ground state

The structure and decay of $^{26}$O are investigated in a three-body $^{24}$O+$n+n$ 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 $2n$ emitters due to core recoil and neutron-neutron final state interaction. This effect is far exceeding analogous effect in the true $2p$ emitters. Our calculations provide reasonably narrow boundaries for the lifetime vs.\ decay energy dependence for the true $2n$ emission. An upper limit of $\sim 1$ keV for the decay energy of the unbound $^{26}$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 62^{62}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