Abstract: A sample holder for placing a sample substance for transmission measurements with optical radiation into a spectrometer, in particular, a FTIR spectrometer which is at least partially made from a material transparent to the optical radiation in a intermeshing wavelength region and which exhibits an index of refraction in excess of 1 is configured as a converging lens with a concave surface (11) and a convex surface (12). To take an absorption spectrum of a powder and/or fluid dissolved or suspended sample substance, the sample substance is brought onto the concave surface (11) of the sample holder before the measurement where it, in consequence of the curvature and in contrast to a flat surface, is concentrated in a substantially smaller surface region. The configuration of the sample holder as a converging lens increases the yield of the radiation penetrating through the sample substance onto the detector of the spectrometer configuration.