A New Field Tunable Diode Laser Absorption Spectrometer For Highly Sensitive Measurements of Atmospheric Gases

Abstract

The technique of tunable diode laser absorption spectroscopy (TDLAS) has been employed in a number of field investigations for studying the chemistry of both the lower atmosphere (the troposphere) as well as the middle atmosphere (the stratosphere) over the past several years.1 This technique offers many advantages in such studies including: high sensitivity, high selectivity, high precision, fast response, and versatility. The present paper describes a new field TDLAS system, which has been developed at the National Center for Atmospheric Research (NCAR), for furthering our understanding of tropospheric chemistry using this spectroscopic technique. Several novel features have been incorporated in the present system such as a new commercially-available astigmatic Herriott cell and digital signal processing electronics to further improve system performance and versatility. These aspects will be discussed in the present paper along with recent measurements of formaldehyde employing this system at a remote sampling site in Colorado.