1,091 research outputs found

### Anomalous population of $^{10}$He states in reactions with $^{11}$Li

Structure with the lowest energy observed in the $^{10}$He spectrum populated
in the proton knockout reaction with $^{11}$Li beam has a peak at $1.2-1.5$
MeV. This peak is usually interpreted as a resonant $0^+$ ground state of
$^{10}$He. Our theoretical calculations indicate that this peak is likely to be
a pileup of $1^-$, $0^+$, and $2^+$ excitations with very similar shapes. %We
predict a very specific nature of the $1^-$ excitation in $^{10}$He. Moreover,
the ``soft'' $1^-$ excitation appears to be the lowest one in energy. Such an
anomalous continuum response is traced to the halo structure of $^{11}$Li
providing extreme low energy shift to all the expected continuum excitations.
Competitions of the initial state structure (ISS) and the final state
interaction (FSI) effects on the spectrum and three-body correlations in
$^{10}$He are discussed. Analogous effect of the extreme low-energy shift could
also be expected in other cases of $2n$ emitters populated in reactions with
halo nuclei. Simplified example of the $^{10}$He spectrum in $\alpha$ knockout
from $^{14}$Be, is given. We also discuss limits on the properties of $^{9}$He
stemming from the observed $^{10}$He spectrum.Comment: 10 pages, 13 figure

### Scattering theory with finite-gap backgrounds: Transformation operators and characteristic properties of scattering data

We develop direct and inverse scattering theory for Jacobi operators (doubly
infinite second order difference operators) with steplike coefficients which
are asymptotically close to different finite-gap quasi-periodic coefficients on
different sides. We give necessary and sufficient conditions for the scattering
data in the case of perturbations with finite second (or higher) moment.Comment: 23 page

### Two-proton radioactivity and three-body decay. V. Improved momentum distributions

Nowadays quantum-mechanical theory allows one to reliably calculate the
processes of 2p radioactivity (true three-body decays) and the corresponding
energy and angular correlations up to distances of the order of 1000 fm.
However, the precision of modern experiments has now become sufficient to
indicate some deficiency of the predicted theoretical distributions. In this
paper we discuss the extrapolation along the classical trajectories as a method
to improve the convergence of the theoretical energy and angular correlations
at very large distances (of the order of atomic distances), where only the
long-range Coulomb forces are still operating. The precision of this approach
is demonstrated using the "exactly" solvable semianalytical models with
simplified three-body Hamiltonians. It is also demonstrated that for heavy 2p
emitters, the 2p decay momentum distributions can be sensitive to the effect of
the screening by atomic electrons. We compare theoretical results with
available experimental data.Comment: 13 pages, 18 figure

### Scattering Theory for Jacobi Operators with Steplike Quasi-Periodic Background

We develop direct and inverse scattering theory for Jacobi operators with
steplike quasi-periodic finite-gap background in the same isospectral class. We
derive the corresponding Gel'fand-Levitan-Marchenko equation and find minimal
scattering data which determine the perturbed operator uniquely. In addition,
we show how the transmission coefficients can be reconstructed from the
eigenvalues and one of the reflection coefficients.Comment: 14 page

### Inverse scattering transform for the Toda hierarchy with steplike finite-gap backgrounds

We provide a rigorous treatment of the inverse scattering transform for the
entire Toda hierarchy for solutions which are asymptotically close to (in
general) different finite-gap solutions as $n\to\pm\infty$.Comment: 10 page

### From Coulomb excitation cross sections to non-resonant astrophysical rates in three-body systems: $^{17}$Ne case

Coulomb and nuclear dissociation of $^{17}$Ne on light and heavy targets are
studied theoretically. The dipole E1 strength function is determined in a broad
energy range including energies of astrophysical interest. Dependence of the
strength function on different parameters of the $^{17}$Ne ground state
structure and continuum dynamics is analyzed in a three-body model. The
discovered dependence plays an important role for studies of the strength
functions for the three-body E1 dissociation and radiative capture. The
constraints on the $[s^2]/[d^2]$ configuration mixing in $^{17}$Ne and on
$p$-wave interaction in the $^{15}$O+$p$ channel are imposed based on
experimental data for $^{17}$Ne Coulomb dissociation on heavy target.Comment: 12 pages, 13 figure

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