First Observation of New Flat Line Fano Profile via an X-Ray Planar Cavity.

A new Fano profile of a flat line is achieved experimentally by manipulating the relative amplitude of the continuum path, when q takes the pure imaginary number of -i in the x-ray regime. The underlying mechanism is that the interference term in the scattering will cancel the discrete term exactly. This new Fano profile renders only an observable continuum along with an invisible response to the discrete state of atomic resonance. The results suggest not only a different strategy to invisibility studies which provides a possible tool to identify weaker structures hidden by the strong white line, but also a new scenario to enrich the manipulations of two-path interference and nonlinear Fano resonance.

The Study of the Low-Lying Valence-Shell Excitations of Hydrogen Sulfide by Fast Electron Impact.

The valence-shell excitations of hydrogen sulfide have been studied by fast electron impact at a collision energy of 1.5 keV and an energy resolution of about 70 meV. By analyzing the variations of intensity and shape of the feature in the range of 5.0-7.5 eV at different scattering angles, the excitation energy of 5.85 ± 0.01 eV and the line width of 0.80 ± 0.01 eV of the 3b21A2 state have been determined. The generalized oscillator strengths of the valence-shell excitations in the energy range of 5.0-9.2 eV of hydrogen sulfide have been determined from the measured spectra. The corresponding optical oscillator strengths have been obtained by extrapolating the generalized oscillator strengths to the limit of zero squared momentum transfer. The integral cross sections have also been systematically determined from the threshold to 5000 eV by means of the BE-scaling method. The presently obtained oscillator strengths and integral cross sections have significant applications in the studies of planetary atmospheres and interstellar gases.