Surface second harmonic generation (SHG) is shown to display optical rotatory effects dependent on the handedness of chiral molecules (2,2′-dihydroxy-1,1′binaphthyl) at various interfaces. The polarization of the surface SHG radiation is rotated with respect to that of the input fundamental radiation in a direction indicative of the chirality of the surface molecules. The origin of SHG-ORD lies in the electric dipole-allowed χ(2) tensor elements, one of which is associated with the handedness of surface species. The SHG-ORD rotation is independent of the density of surface species for an optically pure system, but is dependent on the chiral excess for mixtures of enantiomers. It is wavelength dependent but resonance is not required to observe the rotation. The experiments show that while SHG-ORD has origins quite distinct from ordinary ORD, it can be utilized to measure chiral structures of surfaces.
The short mean-free path expansion used in fluid modeling of scrape-off layer plasmas is often violated for typical discharge parameters, especially by the superthermal particles, which carry most of the heat flux. Thus, the tail of the distribution function can strongly depart from Maxwellian due to nonlocal mean-free path effects, which can modify plasma transport, impurity radiation, and plasma–neutral gas interactions. These nonlocal effects become particularly pronounced for detached plasma conditions that are characterized by sharp gradients in the plasma parameters along the magnetic field. These problems are being addressed by developing one spatial dimension and two velocity variables, fully kinetic, collisional, and time-dependent particle-in-cell code, W1 [Contrib. Plasma Phys. 34, 436 (1994)], and its parallel-computer version, PW1 [Contrib. Plasma Phys. 34, 424 (1996)]. Comparisons are made with the Fokker–Planck code ALLA [Phys. Plasmas 3, 1634 (1996)] and with experimental results. Kinetic effects on probe measurement interpretation, impurity radiation, and parallel heat conductivity due to non-Maxwellian features in scrape-off layer plasmas are considered. Heat conductivity is compared with ad hoc heat flux limit models.
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