HIGH-RESOLUTION SPECTROMETER FOR ATOMIC SPECTROMETRY

Optical spectrometers combining high spectral resolution with multi-pi xel detection are used in atomic spectrometry more than ever. Because of their wide spectral range and powerful detection capability, echell e spectrometers coupled with charge-coupled device (CCD) arrays are of increasing interest. We developed a compact echelle monochromator wit h external order separation for atomic absorption spectrometry with co ntinuum source. Unlike echelle polychromators, in this spectrometer we can exploit the advantages of enlarged detector height, lower stray l ight level and less aberrations. In order to limit the spectral bandwi dth at the entrance slit of the echelle monochromator, we designed a p re-monochromator whose linear dispersion is controlled by varying the prism angle of a liquid reflectioa prism. Both the pre-monochromator a nd the and echelle monochromator are arranged in similar Littrow-mount ings using off-axis paraboloids with 400 mm focal length. The echelle grating with a blaze angle of 76 degrees yields a spectral bandwidth c orresponding to the resolving power of about 140 000 for a 23 mu m wid e slit.