Cooled Multi-pass Cells for Visible and Infrared Spectroscopy

Modeling of Planetary Atmospheres depends in a crucial way on the availability of high quality laboratory data for the molecular constituents assumed for the atmosphere in question. This paper describes two new cooled multi-pass cells which are based on a design originally articulated by Chernin and Baraskala¹ and which are specifically suited for long path length spectroscopy of gaseous samples. This type of cell was first implemented at Denison University² for use in the visible and near infrared in conjunction with tunable dye and diode lasers. The second, at GSFC, is designed for use in the mid to far infrared for use with tunable lead-salt diode lasers. The Denison 3 meter cell is equipped with two sets of first surface Pyrex mirrors using enhanced silver and dielectric coatings. The GSFC 2 meter cell uses gold-coated aluminum mirrors. Details of the mechanical and thermal design and operating specifications such as temperature and pressure ranges will be given along with examples of typical spectra obtained for water vapor and methane. ¹ S. M. Chernin and E. G. Barskaya, Appl. Opt. 30, 51 (1991). ² M. E. Mickelson, L.E. Larson and A. Schubert, J. Geophys. Res. 96, E2 17.507 (1991). Work at Denison University was performed under NASA Planetary Atmospheres Program grant NAG5-4341. Work at Goddard Space Flight Center was supported by NASA Planetary Atmospheres Program RTOP 344-33-80.