The European Physical Journal D最新文献

We report two-photon excited fluorescence of dyes for refracted laser beams by utilizing tailored laser pulses. A fluorescence contrast difference due to phase shaping could be achieved between different coumarin dyes. Particularly, an increased contrast difference is obtained for configurations close to the Brewster angle. Furthermore, by using a subsequent deformable phase plate for spatial shaping it was possible to precisely adjust the laser beam for controlled refraction at the liquid dye surface. A polarization-dependent refraction was observed when directing the shaped laser beam on the curved liquid adhesion meniscus close to the cuvette wall. This results in a refraction-dependent contrast difference. The presented method could be utilized for surface-sensitive biophotonic imaging applications.

We consider the interaction of a two-level atom with two counter-propagating light pulses of different carrier frequencies. To ensure adiabatic interaction, the pulse duration is much longer than both the inverse frequency difference and the maximum Rabi frequencies of the pulses. For the first time, we examine the case where the atom is initially prepared in a superposition of the ground and excited states with a momentum difference corresponding to one-photon recoil. We identify the conditions under which the atom’s final state is determined by the phase difference of the momentum components of the initial atomic wave. Given the large pulse duration, the interference effects depend critically on the rate of spontaneous emission from the excited state. We analyze the role of spontaneous emission using the Monte Carlo wave function method. The results of our calculations elucidate the influence of spontaneous radiation on both the momentum transferred to the atom and the interference outcome of the two atomic waves.

Reported triple differential cross sections (TDCS) for electron-impact ionization of nitrogen molecule have been calculated by employing distorted-wave Born approximation (DWBA) and independent-atom model (IAM), for incident electron energy of 500 eV, and ejected electron energies of 37 eV, 74 eV, and 205 eV, in coplanar asymmetric geometry. Scattering amplitudes of independent nitrogen atoms calculated in the DWBA were used to determine the TDCS of the molecule in IAM. The obtained results are compared to available experimental and theoretical data. Reasonably good qualitative and quantitative agreement was found for low to intermediate ejected electron energies, in terms of binary and recoil peak prediction. Quantitative discrepancies at higher ejected electron energies are attributed to the DWBA limitations.

Compared to natural chiral structures, planar chiral plasmonic nanostructures, which are two-dimensional artificial structures composed of noble metals that break mirror symmetry, are widely applied in fields such as analytical chemistry, pharmaceutical production, and bioanalytical monitoring. Understanding circular dichroism (CD) and its enhancement mechanisms is crucial for these applications. Although a variety of chiral structures have been extensively studied, a deep understanding of the tunability of the CD effect remains insufficient. In particular, helical structures face challenges such as difficult fabrication and poor tunability. In this study, we designed a chiral structure composed of rectangular metal nanorods and metallic spheres, aiming to achieve a significant tunable CD effect by utilizing the connectivity effect of the metal nanorods, reaching an impressive CD value of 0.7. Results calculated by the finite element method show that, near the resonant wavelengths of 710 nm and 730 nm, the spectral responses of ({T}_{++}) and ({T}_{--}), respectively, exhibit peak and valley patterns, thereby generating a substantial CD effect. Fundamentally, this is due to the shifting of the resonance modes at these specific wavelengths under RCP and LCP light. The extent of this shift can be precisely manipulated by altering the width of the rectangular metal nanorods, thus enabling controlled CD effects. Moreover, the CD effect is found to be highly dependent upon the geometric parameters of the designed structures. In summary, these findings contribute significantly to the development of planar chiral plasmonic nanostructures with tunable and large CD effects, providing valuable insights for their optimization and practical applications.

This study focuses on optimizing beam driving modes to enhance laser-target coupling efficiency and improve particle quality in laser-driven ion acceleration. The aim is to increase proton and ion beam energy. Two-dimensional particle-in-cell simulations are conducted to investigate the proton beam generated by a Petawatt laser-driven multilayer target. The results indicate that optimal space overlap between the laser and targets improves energy coupling efficiency. Numerical simulation results indicate that the overlap of two laser pulses in front of the target, specifically at the same focal point, results in the generation of higher-energy ion beams. This result is primarily attributed to the enhanced longitudinal electric field under such conditions, which leads to increased energies of protons and ions. By adjusting the longitudinal size of the CH layer, a high-quality proton beam with a maximum cut-off energy of approximately 290 MeV and a small energy spread of 5.2(%) and 14.7(%) is achieved