Attosecond metrology of atoms has accessed the time scale of the most fundamental processes in quantum mechanics. Transferring the time-resolved photoelectric effect from atoms to molecules ...considerably increases experimental and theoretical challenges. Here we show that orientation- and energy-resolved measurements characterize the molecular stereo Wigner time delay. This observable provides direct information on the localization of the excited electron wave packet within the molecular potential. Furthermore, we demonstrate that photoelectrons resulting from the dissociative ionization process of the CO molecule are preferentially emitted from the carbon end for dissociative
Σ states and from the center and oxygen end for the
Π states of the molecular ion. Supported by comprehensive theoretical calculations, this work constitutes a complete spatially and temporally resolved reconstruction of the molecular photoelectric effect.
Recent progress in the generation of ultra-short laser pulses has enabled the measurement of photoionization time delays with attosecond precision. For single photoemission time delays the most ...common techniques are based on attosecond streaking and the reconstruction of attosecond beating by interference of two-photon transitions (RABBITT). These are pump-probe techniques employing an extreme-ultraviolet (XUV) single attosecond pump pulse for streaking or an attosecond pump pulse train for RABBITT, and a phase-locked infrared (IR) probe pulse. These techniques can only extract relative timing information between electrons originating from different initial states within the same atom or different atoms. Here we address the question whether the two techniques give identical timing information. We present a complete study, supported by both experiments and simulations, comparing these two techniques for the measurement of the photoemission time delay difference between valence electrons emitted from the Ne 2p and Ar 3p ground states. We highlight not only the differences and similarities between the two techniques, but also critically investigate the reliability of the methods used to extract the timing information.
It is well established that electrons can escape from atoms through tunneling under the influence of strong laser fields, but the timing of the process has been controversial and far too rapid to ...probe in detail. We used attosecond angular streaking to place an upper limit of 34 attoseconds and an intensity-averaged upper limit of 12 attoseconds on the tunneling delay time in strong field ionization of a helium atom. The ionization field derives from 5.5-femtosecond-long near-infrared laser pulses with peak intensities ranging from 2.3 x 10¹⁴ to 3.5 x 10¹⁴ watts per square centimeter (corresponding to a Keldysh parameter variation from 1.45 to 1.17, associated with the onset of efficient tunneling). The technique relies on establishing an absolute reference point in the laboratory frame by elliptical polarization of the laser pulse, from which field-induced momentum shifts of the emergent electron can be assigned to a temporal delay on the basis of the known oscillation of the field vector.
Purpose
This study was designed to assess the effect of calcium on the efficacy of DEB during revascularization of steno-obstructive SFA lesions.
Methods
Sixty patients with de novo lesions of the ...superficial femoral artery underwent endovascular treatment with drug eluting balloons (DEB). DEB was selected according to vessel reference diameter (1:1). In case of residual stenosis > 50 % or flow-limiting dissection, postdilatation with conventional balloon or provisional stenting was done. Patients were classified into eight groups according to circumferential distribution of calcium on CT-angiography axial images (from 0° to 360°) and to its length (length < or > 3 cm) evaluated with digital-subtraction-angiography. Ankle-brachial index (ABI), late lumen loss (LLL), target lesion revascularization (TLR), primary (PP) and secondary (SP) patency, major adverse events (MAE), and Rutherford shift were evaluated at 1-year follow-up and correlated with the amount of calcium.
Results
Revascularization was successful in all cases. Flow-limiting dissection occurred in five cases (8.3 %) with a higher circumferential degree of calcium and solved in three cases with postdilatation and in the other two with provisional stenting. DEB effect was lower in patients with higher degree of calcium (>270° vs. <90°): ABI 0.71 ± 0.07 versus 0.92 ± 0.07; LLL 0.75 ± 0.21 versus 0.45 ± 0.1; PP 50 versus 100 %; SP 50 versus 100 %; TLR 25 versus 0 %; MAE 25 versus 0 %.
Conclusions
Calcium represents a barrier to optimal drug absorption. Circumferential distribution seems to be the most influencing factor with the worst effect noticed in 360° calcium presence.
It is well known from numerical and experimental results that the fraction of Rydberg states (excited neutral atoms) created by tunnel ionization declines dramatically with increasing ellipticity of ...laser light, in a way that is similar to high harmonic generation (HHG). We present a method to analyze this dependence on ellipticity, deriving a probability distribution of Rydberg states that agrees closely with experimental (Nubbemeyer et al 2008 Phys. Rev. Lett. 101 233001) and numerical results. We show using analysis and numerics that most Rydberg electrons are ionized before the peak of the electric field and therefore do not come back to the parent ion. Our work shows, for the first time, the similarities and differences in the process that distinguishes formation of Rydberg electrons from electrons involved in HHG: ionization occurs in a different part of the laser cycle, but the post-ionization dynamics are very similar in both cases, explaining why the same dependence on ellipticity is observed.
Despite evidence that waking is associated with net synaptic potentiation and sleep with depression, direct proof for changes in synaptic currents is lacking in large brain areas such as the cerebral ...cortex. By recording miniature EPSCs (mEPSCs) from frontal cortex slices of mice and rats that had been awake or asleep, we found that the frequency and amplitude of mEPSCs increased after waking and decreased after sleep, independent of time of day. Recovery sleep after deprivation also decreased mEPSCs, suggesting that sleep favors synaptic homeostasis. Since stronger synapses require more energy, space, and supplies, a generalized renormalization of synapses may be an important function of sleep.
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