We present a new method for supermassive black hole (SMBH) mass measurements in Type 1 active galactic nuclei (AGN) using polarization angle across broad lines. This method gives measured masses which are in a good agreement with reverberation estimates. Additionally, we explore the possibilities and limits of this method using the STOKES radiative transfer code taking a dominant Keplerian motion in the broad line region (BLR). We found that this method can be used for the direct SMBH mass estimation in the cases when in addition to the Kepler motion, radial inflows or vertical outflows are present in the BLR. Some advantages of the method are discussed.

Modern experimental methods and instruments for X-ray spectral investigation of hot dense plasma provide complex information on environmental conditions in extreme states of matter. The basic spectroscopic conceptions for K-shell plasma diagnosis are outlined, the main characteristics of toroidally bent crystal spectrometers and vertical-dispersion instruments are briefly reviewed. Selected applications (monitoring and optimization of the emission from the femtosecond-laser-produced plasmas, characterization of colliding laser-exploded foils, spectral line merging, and continuum lowering in constrained-flow plasmas) demonstrate the usefulness of advanced spectroscopic methods for plasma diagnostics and fundamental research.