Spectroscopic apparatus

摘要

To cover a wide wavelength bandwidth, a spectroscopic apparatus uses three varied line spacing concave diffraction gratings G 1 to G 3 , the corresponding energy ranges for G 1 , G 2 , and G 3 being 50 to 200, 155 to 350, and 300 to 2200 eV, respectively. In the respective wavelength ranges, the diffraction conditions are satisfied. To provide a high throughput and a high resolution in the respective wavelength regions, the incident angles ± 1 to ± 3 for G 1 to G 3 measured from the normal line of the diffraction grating are specified to be ± 1 < ± 2 < ± 3 . Presupposing the normal lines of all diffraction gratings are superposed upon a common normal line, in order to meet ± 1 < ± 2 < ± 3 , the center positions ” 1 to ” 3 for G 1 to G 3 are set on the normal line (as ” 1 < ” 2 < ” 3 ). From G 1 to G 3 , one diffraction grating can be selected.