Threshold Laws for the Break-up of Atomic Particles into Several Charged Fragments

The processes with three or more charged particles in the final state exhibit particular threshold behavior, as inferred by the famous Wannier law for (2e + ion) system. We formulate a general solution which determines the threshold behavior of the cross section for multiple fragmentation. Applications to several systems of particular importance with three, four and five leptons (electrons and positrons) in the field of charged core; and two pairs of identical particles with opposite charges are presented. New threshold exponents for these systems are predicted, while some previously suggested threshold laws are revised.Comment: 40 pages, Revtex, scheduled for the July issue of Phys.Rev.A (1998

SnO₂ nanoparticles in silica: nanosized tools for femtosecond-laser machining of refractive index patterns

We show that SnO2 nanoclusters in silica interact with ultrashort infrared laser pulses focused inside the material generating a hydrostatic compression and photoelastic response of the surrounding glass. This effect, together with the laser-induced nanocluster amorphization, gives rise to positive or negative refractive-index changes, up to 10–2, depending on the beam-power density. This result points out a wide tuning of the refractive index patterns obtainable in silica-based optical technology

Les noms mycéniens dans les textes hittites

E. Forrer's interpretation of Hittite mTawagalawa as a compounded Greek PN has been widely accepted. His equation mTawagalawa = ̕Eτεϝοκλέϝες, however, causes problems due to the presence of initial syllable ʼE- in Greek, a- timbre of vowel, and the sequence -ga-la- instead of -ak-la- in Hittite. It seems more plausible to segment the name as T(a)wako-lâwos which finds a perfect parallel in Greek PN Σακόλαος, `The shield of the people'.La interpretación de E. Forrer del hitita mTawagalawa como un nombre propio compuesto griego ha sido ampliamente admitida. Su ecuación mTawagalawa = ̕Eτεϝοκλέϝες origina, sin embargo, problemas, debido a la presencia de la sílaba inicial ʼE- en griego, timbre de vocal a-, y la secuencia -ga-la- en lugar de la hitita -ak-la-. Parece más plausible segmentar el nombre como T(a)wako-lâwos, que encuentra un paralelo perfecto en el nombre propio griego Σακόλαος, 'El escudo del pueblo'. (Traducción del inglés para esta versión electrónica

Harmonic oscillators and resonance series generated by a periodic unstable classical orbit

The presence of an unstable periodic classical orbit allows one to introduce the decay time as a purely classical magnitude: inverse of the Lyapunov index which characterizes the orbit instability. The Uncertainty Relation gives the corresponding resonance width which is proportional to the Planck constant. The more elaborate analysis is based on the parabolic equation method where the problem is effectively reduced to the multidimensional harmonic oscillator with the time-dependent frequency. The resonances form series in the complex energy plane which is equidistant in the direction perpendicular to the real axis. The applications of the general approach to various problems in atomic physics are briefly exposed

Two-photon absorption properties of commercial fused silica and germanosilicate glass at 264 nm

Using high-intensity femtosecond pulses at lambda=264 nm, we have measured the two-photon absorption (TPA) coefficient in three fused silica samples Suprasil, Herasil, Infrasil (Heraeus) and in 3.5 mol % Ge-doped fused silica. While in fused silica samples the TPA coefficient value is about 2x10(-11) cm/W, in germanosilicate glass it equals (42+/-3)x10(-11) cm/W. (C) 2002 American Institute of Physics. (DOI: 10.1063/1.1448387

Erratum: "Ultraviolet poling of pure fused silica by high-intensity femtosecond radiation" [Appl. Phys. Lett. 86, 071106 (2005)]

Erratu