Search results for "Persio"

Finite-energy sum rules and finite dispersion relations for K*→Kππ transitions

1977

Dispersive analysis of the γγ⁎ → ππ process

2019

Abstract We present a theoretical study of the γ γ ⁎ → π + π − , π 0 π 0 processes from the threshold through the f 2 ( 1270 ) region in the ππ invariant mass. We adopt the Omnes representation in order to account for rescattering effects in both s- and d-partial waves. For the description of the f 0 ( 980 ) resonance, we implement a coupled-channel unitarity. The constructed amplitudes serve as an essential framework to interpret the current experimental two-photon fusion program at BESIII. They also provide an important input for the dispersive analyses of the hadronic light-by-light scattering contribution to the muon's anomalous magnetic moment.

Kerr frequency comb generation in the normal dispersion regime of dispersion oscillating telecom fiber

2013

The generation of optical frequency combs has a variety of applications from optical metrology to spectroscopy and wavelength division multiplexing. Nonlinear methods to generate frequency combs are based on multiple four-wave mixing (FWM) in highly nonlinear waveguides [1]. The mechanism for the generation of a wideband comb from a CW pump is Kerr-induced phase-matching of the FWM interaction or modulation instability (MI), which requires operating in the anomalous dispersion regime. Such restriction can be circumvented with a cavity geometry, where MI [2] and comb generation [3] may also be observed in the normal dispersion region. Alternatively, one may obtain MI and unequally spaced Ker…

Femtosecond parabolic pulse shaping in normally dispersive optical fibers

2013

Formation of parabolic pulses at femtosecond time scale by means of passive nonlinear reshaping in normally dispersive optical fibers is analyzed. Two approaches are examined and compared: the parabolic waveform formation in transient propagation regime and parabolic waveform formation in the steady-state propagation regime. It is found that both approaches could produce parabolic pulses as short as few hundred femtoseconds applying commercially available fibers, specially designed all-normal dispersion photonic crystal fiber and modern femtosecond lasers for pumping. The ranges of parameters providing parabolic pulse formation at the femtosecond time scale are found depending on the initia…

Engineered surface waves in hyperbolic metamaterials

2013

We analyzed surface-wave propagation that takes place at the boundary between a semi-infinite dielectric and a multilayered metamaterial, the latter with indefinite permittivity and cut normally to the layers. Known hyperbolization of the dispersion curve is discussed within distinct spectral regimes, including the role of the surrounding material. Hybridization of surface waves enable tighter confinement near the interface in comparison with pure-TM surface-plasmon polaritons. We demonstrate that the effective-medium approach deviates severely in practical implementations. By using the finite-element method, we predict the existence of long-range oblique surface waves. This research was fu…

Reply to "Comment on 'Dispersion Interaction between Two Hydrogen Atoms in a Static Electric Field' "

2020

In their Comment on our Letter Dispersion Interaction between Two Hydrogen Atoms in a Static Electric Field, P. P. Abrantes et al. address one of the main points discussed in our Letter, that is, the possibility to manipulate interatomic interactions through an external static electric field. In our Letter, we have shown that the interaction between two ground-state atoms can be significantly modified, exploiting an external static electric field, and even turned from attractive to repulsive, depending on the strength of the external field and the geometrical configu- ration. In their Comment, Abrantes et al. point out that it is the electrostatic contribution between the electric dipoles i…

Gamma radiation induced polymerization of vinyl monomers in dense CO2

2002

Abstract The dispersion polymerization of methyl methacrylate in dense carbon dioxide, initiated by γ-rays, utilizing different polysiloxanes as polymeric stabilizers, was investigated. The progress of the reaction, as a function of the irradiation dose, was also studied and the occurrence of a gel effect has been detected. For comparison, the dispersion polymerization has been carried out in supercritical conditions ( T =65°C and 38 MPa) in the presence of 2,2′-azobis(isobutyronitrile) (AIBN) as initiator. High molecular weight polymer (M w > 1000 kg/mol) with narrow molecular weight distribution has been obtained both with γ-rays and AIBN. The electron scanning micrographs show that regul…

Peculiarities of coherent optical oscillation in Sn_2P_2S_6 crystals

2010

We show analytically and numerically that the unusual photorefractive nonlinear response of Sn2P2S6 crystals leads to a variety of new features of coherent optical oscillation. In addition to the explanation of the known peculiarities, new features are predicted.

Dispersion Forces and Counterintuitive Steric Effects in Main Group Molecules: Heavier Group 14 (Si-Pb) Dichalcogenolate Carbene Analogues with Sub-9…

2013

The synthesis and spectroscopic and structural characterization of an extensive series of acyclic, monomeric tetrylene dichalcogenolates of formula M(ChAr)2 (M = Si, Ge, Sn, Pb; Ch = O, S, or Se; Ar = bulky m-terphenyl ligand, including two new acyclic silylenes) are described. They were found to possess several unusual features-the most notable of which is their strong tendency to display acute interligand, Ch-M-Ch, bond angles that are often well below 90°. Furthermore, and contrary to normal steric expectations, the interligand angles were found to become narrower as the size of the ligand was increased. Experimental and structural data in conjunction with high-level DFT calculations, in…

Effects of spatial dispersion and damping on exciton absorption

1986

Exciton absorption is studied in the spatially dispersive case. The energy-propagation properties of the medium are used to define the absorption coefficient. The interplay of dispersion and damping in determining the absorption coefficient is discussed and a critical value of the damping above which the dispersion effects disappear is derived analytically. Furthermore, the dependence of the spectral and of the integrated absorption coefficient on the auxiliary boundary condition is discussed.