Helium Abundance Detector

A number of the Galileo probe s instruments were designed, therefore, to detect the abundance of chemical species present in the atmospheres of both Jupiter and the Sun. One instrument, the Helium Abundance Detector, was designed specifically to measure the amount of helium in the Jovian atmosphere. It found a value for the ratio of helium to hydrogen (He H) of 0.157, which is 0.81 that found in the Sun. Why does Jupiter have so much less helium in its atmosphere than the Sun ... 

Apart from innovative ideas in chemistry, progress in the field of matrix i.solation is closely coupled with the development of new instruments and devices. Fourier-transform infrared instruments have enormously increased the amount of information which is obtained from matrix-isolation experiments. With new helium-cooled infrared detectors and faster Fourier-transform processors, less time is required to obtain high-quality spectra over a large spectral range. Unusual species at low concentrations and isotopic molecules with a low natural abundance can therefore now be detected. Additionally, hidden data are easily accessible by spectra subtraction (e.g., of the spectra before and after photolysis). 

Positive ion fast atom bombardment (FAB) mass spectra were obtained with the JEOL HXllO/HXllO tandem double-focusing mass spectrometer with JEOL gun and collisionally induced decomposition (CID) MS/MS. The JEOL instrument was operated at +10 kV with -20 kV postacceleration at the detector. The xenon neutral beam had 6 kV acceleration from the JEOL gun. CID MS/MS was performed with 1 1000 resolution in both MS-1 and MS-2. Helium was used as the collision gas at a pressure sufficient to reduce precursor ion abundance by 75%. Samples were dissolved in methanol-glycerol (1 1, v/v) for all FABMS analyses. 

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