Search results for "Optical physics"
showing 10 items of 35 documents
Dimer dissociation energies of small odd-size clusters
2002
The dimer dissociation energies of gold cluster ions Au + n , n = 9, 11, 13, 15 have been determined with an extension of a recently developed model-independent method. Monomer-dimer decay pathway branching ratios provide the energy dependent process which is needed in this method. The measured values are D 2 ( Au + 9 ) = 3.66(8)(9) eV, D 2 ( Au + 11 ) = 4.27(11)(8) eV, D 2 ( Au + 13 ) = 4.50(9)(7) eV and D 2 ( Au + 15 ) = 4.29(10)(6) eV.
Loss induced collective subradiant Dicke behaviour in a multiatom sample
2005
The exact dynamics of $N$ two-level atoms coupled to a common electromagnetic bath and closely located inside a lossy cavity is reported. Stationary radiation trapping effects are found and very transparently interpreted in the context of our approach. We prove that initially injecting one excitation only in the $N$ atoms-cavity system, loss mechanisms asymptotically drive the matter sample toward a long-lived collective subradiant Dicke state. The role played by the closeness of the $N$ atoms with respect to such a cooperative behavior is brought to light and carefully discussed.
Mechanical entanglement detection in an optomechanical system
2017
We propose here a setup to generate and evaluate the entanglement between two mechanical resonators in a cavity optomechanical setting. As in previous proposals, our scheme includes two driving pumps allowing for the generation of two-mode mechanical squeezing. In addition, we include here four additional probing tones, which allow for the separate evaluation of the collective mechanical quadratures required to estimate the Duan quantity, thus allowing us to infer whether the mechanical resonators are entangled.
Coherent and incoherent phonon processes in artificial atoms
2003
Carrier-phonon interaction in semiconductor quantum dots leads to three classes of phenomena: coherent effects (spectrum reconstruction) due to the nearly-dispersionless LO phonons, incoherent effects (transitions) induced by acoustical phonons and dressing phenomena, related to non-adiabatic, sub-picosecond excitation. Polaron spectra, relaxation times and dressing-related decoherence rates are calculated, in accordance with experiment.
Hot electrons and nonlinear optical nanoantennas
2017
The large field enhancement generated at the surface of a resonant plasmonic nanoparticle, or optical antennas, is the key mechanism that eventually led to the development of nonlinear plasmonics [1-2]. While the resonance may boost the nonlinear yield of an adjacent structure or surrounding medium, it was soon realized that optical antennas possess nonlinear coefficients comparable or exceeding those of standard nonlinear optical materials [3]. We discuss here two nonlinear optical processes — incoherent multi-photon luminescence (MPL) and coherent second-harmonic generation (SHG) — emitted from gold rod optical antennas upon local illumination with a tightly focused femtosecond near-infra…
Alignment-orientation conversion in molecules in an external magnetic field caused by a hyperfine structure
2000
The paper presents a discussion on the problem of alignment-orientation conversion in an excited state of molecules. It is shown that a rather strong alignment-orientation conversion effect in the excited molecular state can be caused by a joint action of an external magnetic field and hyperfine interaction. The orientation thus created is transverse, i.e. perpendicular to the direction of the external magnetic field. The magnitude of this effect is analyzed as dependent on molecular parameters.
Laser-driven amplification of soft X-rays by parametric stimulated emission in neutral gases
2010
The high-order harmonics of short laser pulses created in a nonlinear medium are a useful source of extreme-ultraviolet and soft-X-ray radiation. A newly discovered phenomenon that amplifies this emission even further could improve the efficiency of short-wavelength light sources.
Theoretical study of energy transfer in Rb(7S) + Rb(5S) and Rb(5D) + Rb(5S) collisions
2000
We present results of theoretical studies of the non-resonant excitation transfer in Rb(7S) + Rb(5S) and Rb(5D) + Rb(5S) collisions at thermal collision energies. Rb2 adiabatic molecular terms correlating with the 5S+7S, 5S+5D and 5P+5P states of separated atoms were calculated for internuclear distances R > 20 a.u. using asymptotic approximation. Mechanisms of collisional population and quenching of the 5D state were treated on the basis of the computed molecular terms, and the respective cross-sections were calculated. Theoretical cross-sections are in good agreement with the experimental values at thermal collision energies (\(\) K).
Stark broadening of hydrogen spectral lines with fine structure effects
2004
Formalism and numerical code have been elaborated for calculation of hydrogen line profiles in conditions of plasma in which Stark broadening and fine energy splitting are comparable and it is not possible to neglect either of them. It corresponds to the range of electron densities $10^{11} < N_e ({\rm cm}^{-3}) < 10^{15}$ . Lamb shift and spontaneous emission effects have also been included. Computer simulation method was applied in the calculations. Final results have been compared with experimental and theoretical findings by other authors.
Quasienergy states of trapped ions
2000
The quantum models for a single trapped ion are extended to the description of the collective dynamics for systems of ions confined in quadrupole electromagnetic traps with cylindrical symmetry. A class of quantum Hamiltonians with suitable axial and radial interaction potentials given by homogeneous functions of degree (-2) and invariant under translations and axial rotations are introduced. The considered axial and radial quantum Hamiltonians for the center-of-mass and relative motions are described by collective dynamical systems associated to the symplectic group \(\). Discrete quasienergy spectra are obtained and the corresponding quasienergy states are explicitly realized as \(\) cohe…