We investigate forward scattering of ionization from neon, argon, and xenon in ultrahigh intensities of 2 × 10(19) W/cm(2). Comparisons between the gases reveal the energy of the outgoing photoelectron determines its momentum, which can be scattered as far forward as 45° from the laser wave vector k(laser) for energies greater than 1 MeV. The shell structure in the atom manifests itself as modulations in the photoelectron yield and the width of the angular distributions. We arrive at an agreement with theory by using an independent electron model for the atom, a dipole approximation for the bound state interaction, and a relativistic, three-dimensional, classical radiation field including the laser magnetic field. The studies provide the atomic physics within plasmas, radiation, and particle acceleration in ultrastrong fields.
Recollision for a laser driven atomic system is investigated in the relativistic regime via a strong field quantum description and Monte Carlo semiclassical approach. We find the relativistic recollision energy cutoff is independent of the ponderomotive potential Up, in contrast to the well-known 3.2Up scaling. The relativistic recollision energy cutoff is determined by the ionization potential of the atomic system and achievable with non-negligible recollision flux before entering a “rescattering free” interaction. The ultimate energy cutoff is limited by the available intensities of short wavelength lasers and cannot exceed a few thousand Hartree, setting a boundary for recollision based attosecond physics
Patients with probable Alzheimer's disease (AD) are reported to show mild, but reliable, difficulties reading aloud and spelling to dictation exception words, which have unusual or unpredictable correspondence between their spelling and pronunciation (e.g., touch). To understand the cognitive dysfunction responsible for these impairments, 21 patients and 27 age-and education-matched controls completed specially designed tests of single-word oral reading and spelling to dictation. AD patients performed slightly below controls on all tasks and showed mildly exaggerated regularity effects (i.e., the difference in response accuracy between words with regular spellings minus exception words) in reading and spelling. Qualitative analyses, however, did not demonstrate response patterns consistent with impairment in central lexical orthographic processing. The authors conclude that the mild alexia and agraphia in AD reflect semantic deficits and nonlinguistic impairments rather than a specific disturbance in lexical orthographic processing.
The strong and ultrastrong field-molecule interaction is a complex, many-body process involving multiple ionization processes. We present ion yields and molecular fragment energies for the ionization of chloromethane (CH 3 Cl) in a laser field with intensities spanning from 10 14 to 10 17 W cm −2 . As the laser intensity increases, ionization of CH 3 Cl is observed to pass from molecular tunneling, to enhanced ionization (EI), to an atomic-like response. The energy spectra of the ions show no dependence on the intensity and has its source in dissociative molecular ionization. A classical model of an aligned C-Cl ion is used to model the interaction. Following an initial molecular ionization process, our results show EI is a driving influence in the formation of low charge states until ionization become atomic-like and involves tightly bound ion states whose ionization is unaffected by nearest neighbor ions of similar ion charge.
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