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Theard, L. P.

Publications and source records attributed to Theard, L. P..

4 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Variable fragmentation mass spectrometry using chemi-ionization

A description is given of experiments which provide a verification of three features of Penning ionization mass spectrometry. One of these features is related to the ability to simplify a molecular fragmentation pattern and to intensify the molecular ion peak. Another feature is concerned with the ability to identify uniquely geometric isomers which are indistinguishable using high-energy electron impact methods. The third feature involves the ability to identify components in a mixture, which cannot be discerned using electron impact or chemical ionization methods alone. The investigation shows that Penning ionization is an efficient soft ionization technique which can be used to simplify mass spectra of pure compounds as well as mixtures.

Laudenslager, J. B.↗
NASA NTRS1975

Proton transfer reactions from H3/+/ ions to N2, O2, and CO molecules

The rate constants for proton transfer from H3(+) ions to N2, O2, and CO have been measured as function of hydrogen-buffer-gas partial pressure. The rate constant for proton transfer from H3(+) to N2 shows a very large pressure dependence, increasing from 1.0 by 10 to the -9th power cu cm/s at low H2 partial pressures to 1.7 by 10 to the -9th power cu cm/s at high H2 partial pressures. The rate constants for proton transfer from H3(+) to O2 and CO are constant with partial pressure of H2. The roles of excess vibrational energy in H3(+) ions and of equilibrium between forward and back reactions are discussed. Back reaction is observed only for the reaction of H3(+) ions with O2, and an equilibrium constant of 2.0 (plus or minus 0.4) at 298 K has been determined. From these data, the proton affinity of O2 is deduced to be 0.47 (plus or minus 0.11) kcal/mole higher than that of H2.

Kim, J. K.↗
NASA NTRS1974

Ion-molecule reactions and vibrational deactivation of H2/+/ ions in mixtures of hydrogen and helium

Use of ion cyclotron resonance methods to measure the thermal energy rate constants for a number of ion-molecule reactions involving hydrogen and hydrogen-helium mixtures. Assuming that the distribution of initial vibrational states in the H2(+) ion is a near-Franck-Condon distribution, the occurrence of collisional deactivation of vibrationally excited H2(+) ions by He atoms is identified, and an approximate rate constant for the deactivation process and its dependence on vibrational energy are given.

Theard, L. P.↗