Table of contents

The word 'attosecond' (1 as = 10⁻¹⁸ s) officially entered the vocabulary of physics when sub-femtosecond pulses of UV/XUV light produced either by nonlinear frequency conversion of a ultra-short infrared pump pulse or Fourier synthesis of broad bandwidth radiation were established. The physics of these pulses is based on nonlinear, nonperturbative laser–atom interaction: stimulated Raman scattering or high harmonic generation (HHG) is used to generate the necessary bandwidth, which naturally encompasses the visible and UV/XUV spectral range. However, the crucial element for attosecond pulse generation is the control of the spectral phase. New methods of temporal characterization at frequencies lying in the UV/XUV had to be elaborated. These methods rely on the energy/momentum analysis of photoelectrons produced by XUV attosecond flashes in the presence of an intense infrared field whose optical cycle itself becomes the basic clock. Single 650 as pulses have been produced and applied to trace the dynamics of electrons inside atoms following the creation of an inner-shell hole. Periodic combs of 250 as pulses have been synthesized by superposing just four harmonics and applying to the attosecond timing of the electron motion in HHG. Although it is easy to increase the bandwidth by coupling more harmonics, a fundamental limit to the duration of the light bursts produced has been discovered. It is imposed by the lack of synchronization of the different harmonic orders. The current limit is estimated to be 130 as. The latest advances include a direct autocorrelation of an attosecond pulse train and the production of a single 250 as soft x-ray pulse. This paper offers a snapshot of the state-of-the-art in the production and characterization of attosecond light pulses, with a glimpse at the first steps in attophysics.

This review focuses on the use of accelerator-based methods to investigate the interaction between negative ions and photons, electrons, heavy particles and external electric fields. The goal of negative ion physics is to better understand the role played by electron correlation in the structure and dynamics of many-electron systems. Negative ions are well suited for such studies since they exhibit an enhanced sensitivity to correlation due to the efficient screening of the nucleus by the atomic electrons. The structure of a negative ion is qualitatively different from that of an atom or positive ion. The difference can be traced to the nature of the force binding the outermost electron. In the case of a negative ion, the extra electron moves in a short-range potential arising from the induced dipole associated with the polarization of the atomic core. Typically, this potential supports only a single bound state. Negative ions are studied experimentally by detaching one or more electrons in a controlled manner. Excited states of negative ions are often found embedded in continua above the first detachment threshold. These transient states decay by autodetachment and their presence is manifested as a resonance structure in detachment cross sections.

This review discusses progress in the new field of coherent matter waves, particularly with respect to Bose–Einstein condensates. We give a short introduction to Bose–Einstein condensation and the theoretical description of the condensate wavefunction. We concentrate on the coherence properties of this new type of matter wave as a basis for fundamental physics and applications. The main part of this review treats various measurements and concepts in the physics of coherent matter waves. In particular, we present phase manipulation methods, atom lasers, nonlinear atom optics, optical elements, interferometry and physics in optical lattices. We give an overview of the state of the art in the respective fields and discuss achievements and challenges for the future.

A significant deviation of turbulent transport from conventional diffusion necessitates a search for new types of equations and scalings. Long-range correlations are responsible for anomalous transport. An investigation of correlation effects and correlation functions, which are fairly universal tools, plays an important role. This review deals with the methods of direct calculations, diffusive approximation, and the scaling representation of correlation effects. In this paper, we consider different methods for constructing transport equations, ranging from those in the quasi-linear approximation to those with fractional derivatives. The topics to be discussed include renormalized quasi-linear equations, Levy–Khintchine distributions, and continuous time random walk. A variety of instabilities leads to the development of different turbulence types. This variety of forms requires not only special description methods, but also an analysis of the general mechanisms. One such mechanism is percolation transport. Its description is based on the ideas of long-range correlations, borrowed from the theory of phase transitions, and fractality. A detailed analysis of the more important results obtained in this field is presented in this paper. We will focus on scaling arguments that play an important role in obtaining estimates of transport effects.