We review the hemodynamic, metabolic and cellular parameters affected during early ischemia and their changes as a function of approximate cerebral blood flow ( CBF) thresholds. These parameters underlie the current practical definition of an ischemic penumbra, namely metabolically affected but still viable brain tissue. Such tissue is at risk of infarction under continuing conditions of reduced C

Single ionization of helium by a superposition of selected XUV high harmonics and infrared radiation has been studied by a momentum imaging technique. The measured angular distributions of photoelectrons are compared to numerical time-dependent calculations, showing very good agreement after average. The calculated angular distributions appear to depend critically on the delay between harmonic and

Recent experimental and theoretical work examining the double photoionization of H 2 has uncovered surprising changes in the fully differential cross sections as a function of the kinetic energy released to the protons (which is equivalent to different internuclear separations of the molecule). We describe the recent joint theoretical and experimental investigations which have uncovered the physic

Photo-double ionization (PDI) of xenon by the Ti:Sapphire laser fundamental frequency combined to its 19th and 25th harmonics has been studied by means of a momentum imaging spectrometer. The measurement of the two emitted photoelectrons' momenta and their energy and angular correlations gives insight into the various mechanisms leading to PDI. Although the conditions for non-sequential direct pho

Multi-photon-double ionization of xenon by Ti:Sapphire laser pulses combined with their 25th harmonic has been studied by means of a momentum imaging spectrometer. The determination of the momenta of the emitted photoelectron pair and of its energy and angular correlation gives insight into the various mechanisms leading to double ionization. Although the conditions for non sequential direct multi

A physical interpretation is given for the variation with internuclear separation of the fully differential cross section for double photoionization of H2. This effect is analyzed in a geometry where the fourbody interaction is completely probed. Excellent agreement is found between experiment and time-dependent close-coupling theory after convoluting the latter over the relevant solid angles. We

The Coulomb explosion of the hydrogen molecule, after absorption of a 76 eV photon, has been studied by momentum imaging the two electrons and the two protons. Absolute fully differential cross sections (FDCS) are compared with Time Dependent Close Coupling (TDCC) calculations and the first-order helium-like model in the coplanar geometry for equal electron energy sharing. While the helium-like mo

Xenon multiphoton double ionization pathways are studied in a reaction microscope using a pump-probe arrangement of extreme ultraviolet high harmonic and infrared laser radiation. The momentum of photoelectrons is recorded in coincidence with singly or doubly charged ions. Among all possible routes to multiphoton double ionization, sequential processes using ionic excited states as intermediate st

The Coulomb explosion of the hydrogen molecule, after absorption of a 76eV photon, has been studied by momentum imaging the two electrons and the two protons. Absolute fully differential cross sections of high statistical quality are obtained. A subset of the overall data, namely, equal electron-energy sharing, is used to investigate the effects of molecular orientation on the photoelectron angula

2-color Xe photo-double-ionization is investigated after absorption of one XUV high order harmonic photon and few infrared Ti:Sapphire laser photons. Double ionization is found to happen predominantly step wise via intermediate excited Xe+ states.

Two-colour experiments combining synchrotron radiation and light pulses from a synchronized linear dye laser have been performed to investigate even-parity Xe* 5p5 (2P1/2) np′ and nf′ resonances of atomic xenon. These autoionization states have been reached through a double-resonant excitation scheme including the short-lived intermediate states Xe* 5p5(2P3/2) 5d and 6d. Our theoretical results re

Energy- and angle-resolved photoionization spectra of He irradiated by linearly polarized intense 810 nm laser radiation and several of its XUV odd harmonics are investigated. The angular distribution of the odd-order peaks, produced by single-photon ionization by one harmonic, is, surprisingly, broadened by the IR field. The even-order ones, due to two-colour, two-photon ionization, show at 90° l

Photo double ionization of xenon in the vicinity of the threshold is investigated using high harmonics and a reaction microscope. Electron momentum and energy distributions, β-asymmetry parameters and momentum correlation are measured at 32.4 nm. The results agree with previous measurements where available. The advantages and limits of the method are discussed.

Two-color experiments combining synchrotron radiation from the SuperACO storage ring in Orsay (France) and conventional dye lasers have been performed to investigate excited atoms and molecules. Synchronization between synchrotron and laser pulses has been applied to study even-parity Xe*5p5 mf′,. np′ autoionization states of atomic xenon via the short-lived intermediate states Xe* 5p5 (2P3/2) 5d

The relaxation processes of inner-shell excited N molecules were studied using dispersed fluorescence spectroscopy in the wavelength region 250≤λfluo≤1000 nm. For molecular states, the decay of the N2 + B 2Σu state was analyzed under vibrational resolution. Strong intensities for emissions from neutral and singly charged atomic fragments were observed.

The fluorescence emission following inner-shell excitation of molecules has been analyzed in the wavelength region 300 nm≤λfluo≤1000 nm. The main contributions to the experimental spectrum are due to transitions of the parent molecules ionized in the outer valence shells as well as to the radiative decay of excited photofragments, mainly neutral and singly charged atoms. As an example, the dispers

The technique of synchronization between the pulses of a linear dye laser, synchronously pumped by a mode-locked Ar+ laser, and the synchrotron radiation pulses from the SuperACO storage ring in Orsay (France) has been applied to study the photoionization of the Xe* 5p55d [3/2]1 and Xe* 5p56d [3/2]1 excited states in the energy region between the Xe+ 5p5(2P3/2) and (2P1/2) thresholds. The experime

The light pulses of a mode-locked Ar+ laser have been synchronized to the synchrotron radiation pulses of the SuperACO storage ring in Orsay. In order to test the feasibility and to demonstrate the capability for the investigation of free atoms we have studied the two-photon ionization of atomic Helium and Xenon via the He* 1s3p and Xe* 5p55d resonant state, respectively. The experimental results

Considerable progress in the investigation of the electronic and vibrational properties of atoms, molecules, materials, surfaces and interfaces has been achieved by combining different photon sources of complementary characteristics. In this paper some experimental results obtained recently at LURE by using two synchronized sources, such as the IR free-electron laser (FEL) CLIO, the VUV storage ri