Cross sections for electron-H&O+ recombination have been measured over an electron energy range of 0.060 -1.15 eV by using a trapped-ion technique to contain an ion sample at a temperature of =400 K. The cross section deduced from these measurements can be represented by cr=4.6 x10-isE ' cm for 0.038 & E -0.110 eV; 0=4.8xl0 E '~c m for 0.110 & E~0.420 eV; and 0=7.5x10 'VE~c m for E &0.420 eV. Uncertainties are estimated to be at the +50% level. Recombination-rate coefficients were calculated from the deduced cross sections, assuming a Maxwellian electron velocity distribution and trial forms for the cross section below 0.038 eV. Assuming the theoretical E~b ehavior for the cross section just above zero energy and comparing with the measured rate coefficient of Leu et al, . at 540 K, we can deduce consistent cross sections below 0.038 eV to be 0=6.0 x10~k cm for 0 & E& 0.023 eV, and 0=4.6x10 E ' cm for 0.023 & E & 0.038 eV.The calculated rate coefficients have temperature dependence T, '5 at 50 K and T, at 105 K, and values of the coefficient are in good agreement with all direct measurements.

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Development of a technique that uses a low-pressure microwave-induced plasma (MIP) for selective elemental detection In a combined gas chromatograph/mass spectrometer (GC-MS) system is described. With this technique, complex organic molecules are converted Into a few simple neutral species by passage through the MIP unit. The elements present In the original molecules determine which species will be formed in the MIP. In a hydrogen-rich plasma, oxygen forms CO and H20, sulfur forms CS2, nitrogen forms HCN, chlorine forms HCI, and carbon forms, CH4, C2H2, C2H4, and C2He. Identification and quantification of these simple neutral species enable elemental composition information for the original molecules to be determined. Detection of elemental C, N, O, S, and Cl and measurement of elemental C/O and C/N ratios In a variety of compound types and structures by the MIP/GC-MS technique are discussed. With the relatively unsophisticated mode of operation used, the dynamic range for the technique Is 400, and the sensitivity limit for elemental carbon passing through the MIP Is 0.3 yug/s.

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