We successfully observed the synchrotron-radiation-based Mössbauer absorption spectra with 158Gd and 99Ru. Their nuclear resonant energies were 79.5 keV and 89.6 keV, respectively, and they are factually the highest energy which energy region synchrotron radiation covers with sufficient intensity as the incident X-rays for Mössbauer spectroscopy. Although the low recoilless fraction owing to these high resonant energy, Mössbauer energy spectra of GdPd3 to 158Gd2O3 and fcc-Ru nanoparticles to bulk hcp-99Ru metal were obtained with natural samples of the former compounds with sufficient amount, because of the high transparency of these high energy X-rays(to electronic scattering). In spite of large statistical errors, we can evaluate the hyperfine parameters when the spectrum includes simple 1-site profile. 99Ru and 158Gd SR-based Mössbauer absorption spectra of various complex materials including somewhat complex structures will be available with the improvements to the measurement system; More detector elements for larger solid angle subtended to the scatterer sample will yields more counting rates and improvement higher recoilless fraction by arranging more appropriate chemical specimen as the scatterer yields deeper absorption profile.
