The chemical properties of the particulate exhaust emissions from an in-use commercial aircraft engine were characterized in April 2004 as part of the Aircraft Particle Emissions Experiment. The test aircraft was the NASA DC-8 equipped with CFM56-2-C1 engines and the test matrix included 11 different engine throttle levels, three fuel compositions, and three sampling distances. The variations in particle emissions number, size, mass, and chemical composition were measured using a suite of instruments, including an aerosol mass spectrometer. The particle emissions were characterized by a trimodal size distribution. The largest mode was dominated by ambient accumulation mode particles mixed into the plume. The middle mode consisted of carbon soot with sulfate and organic coatings. The smallest mode was completely volatile and consisted of sulfate and organic components. The soot emission indices increased with power from 2-120 mg=kg fuel. The semivolatile components increased with distance and decreased with power from 33-5 mg=kg fuel. The sulfate emissions increased with distance and fuel sulfur content. The emissions under low power were dominated by organics, and the high-power conditions were dominated by soot. The CFM56 engine was less efficient at the low thrust levels typically used on the ground at an airport.

Changes in ion abundance from the plasma of an abnormal dc glow discharge, using a copper cathode, have been studied as a function of ͑a͒ gas residence time in the discharge and ͑b͒ the amount of H 2 added to the positive column, without disturbing the discharge. The ArϩH 2 spectra show a severe, but selective, quenching of the ionization. All major ions are quenched except for Cu ϩ , which increases in abundance. It is shown that this cannot be explained by either ion-molecule reactions or the fast recombination suggested previously ͓R. F. G. Meulenbroeks et al., Phys. Rev. E 49, 4397 ͑1994͔͒ for such mixtures. The kinetic behavior is consistent with the heavy involvement of stepwise ionization processes in which high excited metastable states of neutral Ar are precursors for most ions observed in the spectrum. It is proposed that these states are rapidly quenched by H 2 down to the Ar(4s) levels, preventing ionization of most species in the discharge, but significantly boosting the Penning ionization of Cu atoms sputtered from the cathode.

Ions created from the fast-flowing positive column plasma of a glow discharge were monitored using a high voltage magnetic sector mass spectrometer. Since the field gradient and sheath potentials created by the plasma inside the source opposed cation transfer, it is inferred that the ions detected were the field-ionized Rydberg species. This is supported by the mass spectral changes which occurred when a negative bias was applied to the sampling aperture and by the contrasting behavior when attached to a quadrupole analyzer. Reaction with H2 (titrated into the flowing plasma) quenched not only the ionization of discharge gas Rydberg atoms but also the passage of electric current through the plasma, without significant changes to the field and sheath potentials. Few "free" ions were present and the lifetimes of the Rydberg atoms detected were much longer than seen in lower pressure experiments, indicating additional stabilization in the plasma environment. The observations support the model of the flowing plasma, given previously [R. S. Mason, P. D. Miller, and I. P. Mortimer, Phys. Rev. E 55, 7462 (1997)] as mainly a neutral Rydberg atom gas, rather than a conventional ion-electron plasma.