GLASS-TYPE HYDROGEN AND DEUTERIUM ABSORPTION CELLS DEVELOPED FOR D H RATIO MEASUREMENTS IN THE MARTIAN ATMOSPHERE/

Hydrogen and deuterium absorption cells of a new glass type have been developed for the D/H ratio measurements on the Japanese Mars mission PLANET-B. The H/D cells work as narrow-band rejection filters for the H/D Lyman-alpha line, respectively, when the H or D atoms are produced at a heated filament inside the cells. The absorption profiles of the cells were successfully measured with a high-resolution vacuum ultrav iolet spectrometer with a wavelength resolution of 6.6 x 10(-4) nm. Th e derived optical thickness was found to be similar to 7 and similar t o 14 for the hydrogen and deuterium cells, respectively. It was also f ound that the derived temperature of atomic gas ranges between the tem perature of the cell wall and that of the heated filament, and it incr eases with increasing filament temperature. The measured profiles show ed that the absorption efficiencies of the developed absorption cells are sufficient to observe the D/H ratios of the Martian atmosphere. (C ) 1997 Optical Society of America.