Multibeam long-path differential optical absorption spectroscopy instrument: a device for simultaneous measurements along multiple light paths

摘要

A novel long-path differential optical absorption spectroscopy (DOAS) apparatus for measuring tropo-spheric trace gases and the first results from its use are presented: We call it the multibeam instrument. It is the first active DOAS device that emits several light beams simultaneously through only one telescope and with only one lamp as a light source, allowing simultaneous measurement along multiple light paths. In contrast to conventional DOAS instruments, several small mirrors are positioned near the lamp, creating multiple virtual light sources that emit one light beam each in one specific direction. The possibility of error due to scattering between the light beams is negligible. The trace-gas detection limits of NO_(2), SO_(2), O_(3), and H_(2)CO are similar to those of the traditional long-path DOAS instrument.