Sökresultat
Filtrera
Filtyp
Din sökning på "*" gav 534581 sökträffar
Progress in attosecond technology-application to momentum shearing interferometry of electron wavepackets
The recently demonstrated momentum shearing interferometry technique, aimed at recovering phase information about electronic wave packets (EWP) will be presented. Possibilities to improve this technique will be discussed.
Characterization of attosecond pulse trains
Ultrashort light pulses, as short as 100 as, can be produced from high harmonic generation (HHG) in an atomic gas medium. This major achievement of the last 6 years in high field physics has now been demonstrated in different conditions of medium-field interaction [1].
Control of the frequency chirp rate of high harmonic pulses
We measured the frequency chirp rate of harmonics 13 to 23 in argon by cross-correlation with a short femtosecond probe pulse. We directly measured the negative chirp due to the atomic dipole phase and demonstrated that an additional chirp on the pump pulse was transferred to the qth harmonic as q times the fundamental chirp.
Attosecond control of electron localization in one- and two-color dissociative ionization of H2 and D2
We present one-color (IR) and two-color (single attosecond XUV pulse + IR) experiments where the sub-cycle evolution of the electric field of light is used to control the dissociative ionization of hydrogen and deuterium molecules.
Controlling the duration of XUV high order harmonic pulses
We modulate temporally the polarization of a ∼ 30 fs, 800 nm IR pulse and use it to generate high order harmonics. The harmonic emission can clearly be confined and the XUV pulse duration can be continuously tuned from - 5 - 7 fs to 50 fs.
Attosecond excitation of electron wavepackets
We present experiments, supported by time-dependent Schrödinger simulations, on the dynamics of Helium bound states after an attosecond excitation in the presence of a strong infrared laser field.
The ELI-ALPS secondary sources : A getaway to scientific excellence
The essence of ELI-ALPS, the laser driven secondary sources ranging from X-ray and X-UV to THz with duration as short as tens of attoseconds, are designed to be available for users from 2016.
Theory of high-order processes in atoms in intense laser fields Introduction
Many-electron dynamics of heavy atoms in intense laser fields : Effects of screening and correlation
We discuss the role of many-electron interactions in multiphoton multielectron ionization of heavy atoms and try to indicate the relative importance of collective effects and screening, relaxation and shakeup, and Fermi sea correlations. The purpose of the work is to look for approximations in which the photoemission processes have been renormalized in consistent ways with respect to the field and
(Recension av) Hans-Ulrich Wehler, Nationalsocialismen – från massrörelse till Führervälde och utrotningskrig
Spatial profiles of high-order harmonics generated by a femtosecond cr:Lisaf laser
We report the angular distributions of high-order harmonic radiation generated in neon and in argon using a 140 fs Cr:LisAF laser system. The profiles show an evolution from Gaussian to near flat-top. No substructure is observed except at the highest intensity in a completely ionized gas. The divergence of the harmonics is found to depend essentially on whether they belong to the plateau or to the
Propagation effects in high-order harmonic generation in rare gases
We study the role of propagation effects in high-order harmonic-generation experiments. The phase-matching integrals are calculated in the weak-field limit by taking into account the dispersion of the rare-gas medium at each harmonic frequency and the absorption of the harmonics. The refractive indices of the rare gases are deduced from a calculation of the dynamic polarizabilities within the fram
Theoretical aspects of intense field harmonic generation
We present theoretical studies of high-order harmonic generation in a rare-gas medium. The experimental results obtained at Saclay with a 1064 nm Nd-YAG laser in the 1013 W cm-2 intensity range are summarized. The harmonic emission strengths first decrease rather steeply for the first orders, then form a long plateau up to the 21st harmonic in xenon, or up to the 33rd harmonic in argon, before dec
Laser-intensity effects in the energy distributions of electrons produced in multiphoton ionization of rare gases
The energy spectra of electrons produced in multiphoton ionization of rare gases display a large number of peaks corresponding to the absorption of much more than a minimum number of photons required to ionize the atom. A retarding-potential method has been used to analyze the energy of electrons produced in the multiphoton ionization of He, Ne, and Xe at 1064 and 532 nm in a broad range of laser
Optimizing high-order harmonic generation in strong fields
We present high-order harmonic generation results obtained with different laser systems a 1 ps 1053 nm Nd-glass laser a 2 ps 616 nm synchronously pumped dye laser a 36 ps 1064 nm mode-locked Nd-YAG laser and the second harmonics (308 nm and 532 nm) of the latter two systems. We investigate the influence of the laser pulse width the excitation wavelength (from the near infrared to the ultraviolet)
Theoretical aspects of three-photon two-color ionization of xenon through ac-stark-shifted resonant rydberg states
We present a theoretical analysis of a recent experiment [J. Opt. Soc. Am. B 6, 1513 (1989)] on two-color threephotonionization of Xe through resonant even-parity Rydberg states. We calculate second-order ac-Stark shifts, two-photon Rabi frequencies, and ionization widths by using wave functions obtained from a multichannel quantum-defect-theory analysis of the Rydberg series in Xe. We perform a d
Uptake, depuration and sublethal effects of the neonicotinoid, imidacloprid, exposure in Sydney rock oysters
The broad utilisation of imidacloprid (IMI)in agriculture poses an increasing risk to aquatic organisms. However, the potential impacts on commercially important shellfish and chemical residues after exposure, are yet to be assessed. We investigated the levels of IMI in Sydney rock oyster (SRO)tissue during a three-day uptake and four-day depuration cycle using liquid chromatography-mass spectrome
The significance of bicuspid aortic valve after surgery for acute type A aortic dissection
OBJECTIVE: Decision-making concerning the extent of the repair of acute type A aortic dissection (ATAAD) includes functional and anatomical assessment of the aortic valve. We hypothesized that bicuspid aortic valve (BAV) does not impact outcome after surgery for ATAAD. We therefore evaluated the outcome after ATAAD surgery in relation to the presence of BAV, acute aortic regurgitation (AR), and su
Is there a weekend effect in surgery for type A dissection? - Results from the NORCAAD database
BACKGROUND: Aortic dissection type A requires immediate surgery. In general surgery populations, patients operated during weekends have higher mortality rates compared to patients operated on weekdays. The weekend effect in aortic dissection type A has not been studied in detail.METHODS: The Nordic Consortium for Acute Type A Aortic Dissection (NORCAAD) registry includes patients (N=1,159) who und