S XI emission lines in active region spectra obtained with the Solar EUV Rocket Telescope and Spectrograph (SERTS)

Theoretical electron density sensitive emission line ratios involving a total of eleven 2s(2)2p(2)-2s2p(3) transitions in S XI between 187 and 292 Angstrom are presented. A comparison of these with solar active region observations obtained during rocket flights by the Solar EUV Rocket Telescope and Spectrograph (SERTS) reveals generally good agreement between theory and experiment. However, the 186.87 Angstrom line is masked by fairly strong Fe XII emission at the same wavelength, while 239.83 Angstrom is blended with an unknown feature, and 285.58 Angstrom is blended with possibly N IV 285.56 Angstrom. In addition, the 191.23 Angstrom line appears to be more seriously blended with an Fe XIII feature than previously believed. The presence of several new S XI lines is confirmed in the SERTS spectra, at wavelengths of 188.66, 247.14 and 291.59 Angstrom, in excellent agreement with laboratory measurements. In particular, the detection of the 2s(2)2p(2) P- 3(1) -2s2p(3) P-3(0,1) transitions at 242.91 Angstrom is the first time (to our knowledge) that this feature has been identified in the solar spectrum. The potential usefulness of the S XI line ratios as electron density diagnostics for the solar transition region and corona is briefly discussed.

An investigation of catalysts for the on board synthesis of NH3. A possible route to low temperature NOx reduction for lean-burn engines

Platinum group metal catalysts have been investigated for the formation of NH3 from NO + H-2 at low temperatures in the absence and presence of CO. Although CO inhibits the formation of NH3, substantial amounts are still observed with a Pt catalyst. By combining Pt with a support (ceria-zirconia) that has low temperature NOx storage characteristics it has been shown in transient experiments that NH3 can be formed and stored in situ under rich conditions, and may then be used to reduce NOx under lean burn conditions.