Development of Multireflection Absorption Spectroscopy Device using Ultraviolet LED

Abstract

An ultraviolet absorption spectroscopy device using light-emitting diodes (LEDs) as the light source was constructed. The measurement cell, light source, transmitting and receiving optics were installed on a breadboard of 30 cm × 30 cm. A measurement optical path length of 1 m was made possible by multireflection optics. The device can mount two LEDs in tandem, and the transmitted light is coupled to an optical fiber, which is connected to a compact spectrometer. Here, two LEDs of center wavelengths 280 nm and 295 nm were used to provide an emission spectrum which covered the peak region of the absorption spectrum of SO₂. Experiments confirmed the linearity of the absorption coefficient measured by the device for SO₂ concentrations in the range 16-800 ppm.