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Resonant Auger Effect at High X-Ray Intensity
The resonant Auger effect of atomic neon exposed to high-intensity x-ray radiation in resonance with the 1s {yields} 3p transition is discussed. High intensity here means that the x-ray peak intensity is sufficient ({approx} 10{sup 18} W/cm{sup 2}) to induce Rabi oscillations between the neon ground state and the 1s{sup -1}3p ({sup 1}P) state within the relaxation lifetime of the inner-shell vacancy. For the numerical analysis presented, an effective two-level model, including a description of the resonant Auger decay process, is employed. Both coherent and chaotic x-ray pulses are treated. The latter are used to simulate radiation from x-ray free-electron lasers based on the principle of self-amplified spontaneous emission. Observing x-ray-driven atomic population dynamics in the time domain is challenging for chaotic pulse ensembles. A more practical option for experiments using x-ray free-electron lasers is to measure the line profiles in the kinetic energy distribution of the resonant Auger electron. This provides information on both atomic population dynamics and x-ray pulse properties
Prospects for discovering supersymmetric long-lived particles with MoEDAL
We present a study on the possibility of searching for long-lived
supersymmetric partners with the MoEDAL experiment at the LHC. MoEDAL is
sensitive to highly ionising objects such as magnetic monopoles or massive
(meta)stable electrically charged particles. We focus on prospects of directly
detecting long-lived sleptons in a phenomenologically realistic model which
involves an intermediate neutral long-lived particle in the decay chain. This
scenario is not yet excluded by the current data from ATLAS or CMS, and is
compatible with astrophysical constraints. Using Monte Carlo simulation, we
compare the sensitivities of MoEDAL versus ATLAS in scenarios where MoEDAL
could provide discovery reach complementary to ATLAS and CMS, thanks to looser
selection criteria combined with the virtual absence of background. It is also
interesting to point out that, in such scenarios, in which charged staus are
the main long-lived candidates, the relevant mass range for MoEDAL is
compatible with a potential role of Supersymmetry in providing an explanation
for the anomalous events observed by the ANITA detector.Comment: 12 pages, 6 figures; preliminary results presented in
arXiv:1903.11022; matches published version in EPJ
Siegert pseudostates: completeness and time evolution
Within the theory of Siegert pseudostates, it is possible to accurately
calculate bound states and resonances. The energy continuum is replaced by a
discrete set of states. Many questions of interest in scattering theory can be
addressed within the framework of this formalism, thereby avoiding the need to
treat the energy continuum. For practical calculations it is important to know
whether a certain subset of Siegert pseudostates comprises a basis. This is a
nontrivial issue, because of the unusual orthogonality and overcompleteness
properties of Siegert pseudostates. Using analytical and numerical arguments,
it is shown that the subset of bound states and outgoing Siegert pseudostates
forms a basis. Time evolution in the context of Siegert pseudostates is also
investigated. From the Mittag-Leffler expansion of the outgoing-wave Green's
function, the time-dependent expansion of a wave packet in terms of Siegert
pseudostates is derived. In this expression, all Siegert pseudostates--bound,
antibound, outgoing, and incoming--are employed. Each of these evolves in time
in a nonexponential fashion. Numerical tests underline the accuracy of the
method
Copper complexes as chemical nucleases
Redox active mononuclear and binuclear copper(II) complexes have been prepared and structurally characterized. The complexes have planar N-donor heterocyclic bases like 1,10-phenanthroline (phen), dipyridoquinoxaline (dpq) and dipyridophenazine (dppz) ligands that are suitable for intercalation to B-DNA. Complexes studied for nuclease activity have the formulations [Cu(dpq)2(H2O)] (ClO4)2.H2O (1), [CuL(H2O)2(μ-ox)](ClO4)2 (L = bpy,2; phen,3; dpq,4; and dppz,5) and [Cu(L)(salgly)] (L = bpy,6; phen,7; dpq,8; and dppz,9), where salgly is a tridentate Schiff base obtained from the condensation of glycine and salicylaldehyde. The dpq complexes are efficient DNA binding and cleavage active species. The dppz complexes show good binding ability but poor nuclease activity. The cleavage activity of thebis-dpq complex is significantly higher than thebis-phen complex of copper(II). The nuclease activity is found to be dependent on the intercalating nature of the complex and on the redox potential of the copper(II)/copper(I) couple. The ancillary ligand plays a significant role in binding and cleavage activity
Nonfactorization and Color-Suppressed Decays
Using value of the parameter but including a modest
nonfactorized amplitude, we show that it is possible to understand all data,
including polarization, for color-suppressed
decays in all commonly used models of form factors. We show that for decay one can define an effective , which is process-dependent and,
in general, complex; but it is not possible to define an effective for
decay. We also explain why nonfactorized amplitudes do not
play a significant role in color-favored B decays.Comment: 13 pages, Latex, one figure (not included
Sensitivity of nonlinear photoionization to resonance substructure in collective excitation
Collective behaviour is a characteristic feature in many-body systems, important for developments in fields such as magnetism, superconductivity, photonics and electronics. Recently, there has been increasing interest in the optically nonlinear response of collective excitations. Here we demonstrate how the nonlinear interaction of a many-body system with intense XUV radiation can be used as an effective probe for characterizing otherwise unresolved features of its collective response. Resonant photoionization of atomic xenon was chosen as a case study. The excellent agreement between experiment and theory strongly supports the prediction that two distinct poles underlie the giant dipole resonance. Our results pave the way towards a deeper understanding of collective behaviour in atoms, molecules and solid-state systems using nonlinear spectroscopic techniques enabled by modern short-wavelength light sources
Nonfactorization in Hadronic Two-body Cabibbo-favored decays of D^0 and D^+
With the inclusion of nonfactorized amplitudes in a scheme with , we
have studied Cabibbo-favored decays of and into two-body hadronic
states involving two isospins in the final state. We have shown that it is
possible to understand the measured branching ratios and determined the sizes
and signs of nonfactorized amplitudes required.Comment: 15 pages, Late
Investigation of complete and incomplete fusion in Li+Sn reaction around Coulomb barrier energies
The complete and incomplete fusion cross sections for Li+Sn
reaction were measured using online and offline characteristic -ray
detection techniques. The complete fusion (CF) cross sections at energies above
the Coulomb barrier were found to be suppressed by 26 \% compared to the
coupled channel calculations. This suppression observed in complete fusion
cross sections is found to be commensurate with the measured total incomplete
fusion (ICF) cross sections. There is a distinct feature observed in the ICF
cross sections, i.e., -capture is found to be dominant than
-capture at all the measured energies. A simultaneous explanation of
complete, incomplete and total fusion (TF) data was also obtained from the
calculations based on Continuum Discretized Coupled Channel method with short
range imaginary potentials. The cross section ratios of CF/TF and ICF/TF
obtained from the data as well as the calculations showed the dominance of ICF
at below barrier energies and CF at above barrier energies.Comment: 9 pages, 8 figure
A Mild and Efficient Method for the Syntheses and Regioselective Ring-Opening of Aziridines
We have developed a new synthetic method for the synthesis of aziridines using Chloramine-T as an effective reagent in the presence of NH2OH center dot HCl and NaIO4. We found that the same combination of NH2OH center dot HCl and NaIO4 is also very effective for nucleophilic ring opening of aziridines.This research was funded by the Russian Science Foundation, grant number 18-19-00090
Non-Hermitian Rayleigh-Schroedinger Perturbation Theory
We devise a non-Hermitian Rayleigh-Schroedinger perturbation theory for the
single- and the multireference case to tackle both the many-body problem and
the decay problem encountered, for example, in the study of electronic
resonances in molecules. A complex absorbing potential (CAP) is employed to
facilitate a treatment of resonance states that is similar to the
well-established bound-state techniques. For the perturbative approach, the
full CAP-Schroedinger Hamiltonian, in suitable representation, is partitioned
according to the Epstein-Nesbet scheme. The equations we derive in the
framework of the single-reference perturbation theory turn out to be identical
to those obtained by a time-dependent treatment in Wigner-Weisskopf theory. The
multireference perturbation theory is studied for a model problem and is shown
to be an efficient and accurate method. Algorithmic aspects of the integration
of the perturbation theories into existing ab initio programs are discussed,
and the simplicity of their implementation is elucidated.Comment: 10 pages, 1 figure, RevTeX4, submitted to Physical Review
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