Measurements Of Atmospheric Ion Reactions

Charge transfer and charged rearrangement collision cross sections were measured at energies down to 2 eV with identification of product ions and some state selection of primary ions. Electric impact studies of molecular oxygen with high resolution provided new important information on the ionization process, while investigations of negative ions in afterglows of atmospheric gases demonstrated the comparative lack of understanding in this important aspect of atmospheric deionization. The following reactions were studied by the ionization afterglow technique: ionic recombination in O2; thermalization diffusion and electron-ion dissociative recombination in N2; attachment in gases containing NO2; attachment and electron-ion dissociative recombination in gases containing NO. (Author).

Charge transfer and charged rearrangement collision cross sections were measured at energies down to 2 eV with identification of product ions and some state selection of primary ions. Electric impact studies of molecular oxygen with high resolution provided new important information on the ionization process, while investigations of negative ions in afterglows of atmospheric gases demonstrated the comparative lack of understanding in this important aspect of atmospheric deionization. The following reactions were studied by the ionization afterglow technique: ionic recombination in O2; thermalization diffusion and electron-ion dissociative recombination in N2; attachment in gases containing NO2; attachment and electron-ion dissociative recombination in gases containing NO. (Author).

Laboratory measurements indicate that the metastable ions of O(+) in reaction with N2 in the low-energy range (14 eV) react to form principally N2(+), while the ion molecule reaction to form NO(+) has a very small probability. The ground-state O(+) reacts mainly to form NO(+). The abundance of metastable O(+2)D ions was determined using the observation that O(+2)D + N2 has a small cross section for forming NO(+). The ion-energy dependences for both reactions were measured within the energy range 1.0 to 500 eV. (Author).

Metal ions found in the atmosphere above 60 km are the result of incoming meteoroid atmospheric ablation. Layers of metal ions are detected by sounding rocket in situ mass spectrometric sampling in the 80 to 130 km region, which coincides with the altitude region where meteors are observed. Enhancements of metal ion concentrations occur during meteor showers. Even outside of shower periods, the metal ion altitude profiles vary from measurement to measurement. Double layers are frequent at middle latitudes. More than 40 different meteoric atomic and molecular ions, including isotopes, have been detected. Atmospheric metal ions on average have an abundance that matches chrondritic material, the same composition as the early solar system. However there are frequently local departures from this composition due to differential ablation, species dependent chemistry and mass dependent ion transport. Metal ions react with atmospheric O2, O, O3, H2O and H2O2 to form oxygenated and hydrogenated ionic compounds. Metal atomic ions at high altitudes have long lifetimes. As a result, these ions, in the presence of Earth's magnetic field, are transported over long distances by upper atmospheric winds and ionospheric electric fields. Satellite measurements have detected metal ions as high as, approximately 1000 km and have revealed circulation of the ions on a global scale.

Measurements made on the selected-ion flow-tube at the Air Force Geophysics Laboratory on the temperature dependence of several ion-molecule reaction rate coefficients. The N(+) + CO and C(+)+ NO systems were studied over a range of 9 - 450 K. Measurements were also made on C(+) + O2, CO+ + O2, and CO2(+) + O2 over the range 90 - 450 K. Comparison with available earlier results showed agreement within experimental uncertainty. A flowing afterglow apparatus was developed at Oklahoma for the study of ion interactions. Positive-ion/negative ion recombination was studied in this apparatus. Preliminary work was carried out for the Cl2(+) + Cl system and photographic documentation is used to determine the strength of the recombination process. (Author).

A selected ion flow tube apparatus has been modified to include a well-defined flow drift region and instrumentation for ion modulation and data acquisition. This apparatus was used to measure the first experimental mobilities for several important families of atmospheric cluster ions. Core ions include the nitric oxide cation, ammonium ion, and hydronium ion; solvating ligands include water, ammonia, acetonitrile, and acetone. Several collision gases were examined including helium and nitrogen, as well as the polar gases, water and acetone. The mobilities of prototypical aromatic species have also been measured and evaluated to distinguish between isomeric structures. Doppler-resolved laser-induced fluorescence measurements of collision-induced rotational alignment of the molecular nitrogen cation drifted in helium have been carried out. A strong correlation was found between the degree of rotational alignment and the velocity subgroup probed along the field direction; the correlation between alignment and velocity increases with increasing field strength. These results are attributed primarily to the change in anisotropy of the relative velocity vector distribution of the nitrogen cation-helium pair with field strength.

Air Ions: Physical and Biological Aspects fully develops two areas that are important for a comprehensive understanding of the subject of air ions: (1) the physical/chemical nature of ions, and (2) their potential interaction with biological systems. The reader is led through a series of none chapter, the first five of which lay the basis for understanding ions in the context of naturally and artificially created environments. The final four chapters are well situated to discuss the literature and history connected with the search for ion-induced biological effects.

This report investigates experimental measurements of two electron capture for negative ion production in atmospheric gases.