1,081 research outputs found
Anatomy of three-body decay II. Decay mechanism and resonance structure
We use the hyperspherical adiabatic expansion method to discuss the the two
mechanisms of sequential and direct three-body decay. Both short-range and
Coulomb interactions are included. Resonances are assumed initially populated
by a process independent of the subsequent decay. The lowest adiabatic
potentials describe the resonances rather accurately at distances smaller than
the outer turning point of the confining barrier. We illustrate with realistic
examples of nuclei from neutron (He) and proton (Ne) driplines as
well as excited states of beta-stable nuclei (C).Comment: To be published in Nuclear Physics
Unbound states in C populated by -decay of the 16.11 MeV state
The reaction has been used to populate the state at an excitation energy of 16.11 MeV in C. -decay
to unbound states in C are identified from analysis of the decay of the
populated daughter states. Due to a new technique, -decay to the 10.8
MeV 1 state is observed for the first time, and transitions to the 9.64 MeV
(3) and 12.71 MeV (1) are confirmed. Unresolved transitions to natural
parity strength at 10 MeV and 11.5-13 MeV are also observed. For all
transitions partial widths are deducedComment: Corrected small typographical errors and added more details on data
analysi
Investigating 16O with the 15N(p,{\alpha})12C reaction
The 16O nucleus was investigated through the 15N(p,{\alpha})12C reaction at
excitation energies from Ex = 12 231 to 15 700 keV using proton beams from a 5
MeV Van de Graaff accelerator at beam energies of Ep = 331 to 3800 keV. Alpha
decay from resonant states in 16O was strongly observed for ten known excited
states in this region. The candidate 4-alpha cluster state at Ex = 15.1 MeV was
investigated particularly intensely in order to understand its particle decay
channels.Comment: Submitted for Proceedings of Fourth International Workshop on State
of the Art in Nuclear Cluster Physics (SOTANCP4), held from May 13 - 18, 2018
in Galveston, TX, US
Deep rest-frame far-UV spectroscopy of the giant Lyman-alpha emitter 'Himiko'
We present deep 10h VLT/XSHOOTER spectroscopy for an extraordinarily luminous
and extended Lya emitter at z=6.595 referred to as Himiko and first discussed
by Ouchi et al. (2009), with the purpose of constraining the mechanisms
powering its strong emission. Complementary to the spectrum, we discuss NIR
imaging data from the CANDELS survey. We find neither for HeII nor any metal
line a significant excess, with 3 sigma upper limits of 6.8, 3.1, and
5.8x10^{-18} erg/s/cm^2 for CIV 1549, HeII 1640, CIII]
1909, respectively, assuming apertures with 200 km/s widths and offset
by -250 km/s w.r.t to the peak Lya redshift. These limits provide strong
evidence that an AGN is not a major contribution to Himiko's Lya flux. Strong
conclusions about the presence of PopIII star-formation or gravitational
cooling radiation are not possible based on the obtained HeII upper limit. Our
Lya spectrum confirms both spatial extent and flux (8.8+/-0.5x10^{-17}
erg/s/cm^2) of previous measurements. In addition, we can unambiguously exclude
any remaining chance of it being a lower redshift interloper by significantly
detecting a continuum redwards of Lya, while being undetected bluewards
Three-body decays: structure, decay mechanism and fragment properties
We discuss the three-body decay mechanisms of many-body resonances. R-matrix
sequential description is compared with full Faddeev computation. The role of
the angular momentum and boson symmetries is also studied. As an illustration
we show the computed -particle energy distribution after the decay of
12C(1^+) resonance at 12.7 MeV.Comment: 4 pages, 3 figures. Proceedings of the workshop "Critical Stability
of Few-Body Quantum Systems" 200
Effects of a New Triple-alpha Reaction on X-ray Bursts of a Helium Accreting Neutron Star
The effects of a new triple- reaction rate (OKK rate) on the helium
flash of a helium accreting neutron star in a binary system have been
investigated. Since the ignition points determine the properties of a
thermonuclear flash of type I X-ray bursts, we examine the cases of different
accretion rates, , of helium from to , which could cover the
observed accretion rates. We find that for the cases of low accretion rates,
nuclear burnings are ignited at the helium layers of rather low densities. As a
consequence, helium deflagration would be triggered for all cases of lower
accretion rate than . We
find that OKK rate could be barely consistent with the available observations
of the X-ray bursts on the helium accreting neutron star. However this
coincidence is found to depend on the properties of crustal heating and the
neutron star model.We suggest that OKK rate would be reduced by a factor of
for K in the range of the observational errors.Comment: 10 pages, 4 figure
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