Development of lithium attachment mass spectrometry - knudsen effusion and chemical ionisation mass spectrometry (KEMS, CIMS).

Lithium ion attachment mass spectrometry provides a non-specific, non-fragmenting, sensitive and robust method for the detection of volatile species in the gas phase. The design, manufacture and results of lithium based ion attachment ionisation sources for two different mass spectrometry systems are presented. In this study trace gas analysis is investigated using a modified Chemical Ionization Mass Spectrometer (CIMS) and vapour pressure measurements are made using a modified Knudsen Effusion Mass Spectrometer (KEMS).

Measured Saturation Vapor Pressures of Phenolic and Nitro-aromatic Compounds.

Phenolic and nitro-aromatic compounds are extremely toxic components of atmospheric aerosol that are currently not well understood. In this Article, solid and subcooled-liquid-state saturation vapor pressures of phenolic and nitro-aromatic compounds are measured using Knudsen Effusion Mass Spectrometry (KEMS) over a range of temperatures (298-318 K). Vapor pressure estimation methods, assessed in this study, do not replicate the observed dependency on the relative positions of functional groups.

Connecting bulk viscosity measurements to kinetic limitations on attaining equilibrium for a model aerosol composition.

The growth, composition, and evolution of secondary organic aerosol (SOA) are governed by properties of individual compounds and ensemble mixtures that affect partitioning between the vapor and condensed phase. There has been considerable recent interest in the idea that SOA can form highly viscous particles where the diffusion of either water or semivolatile organics within the particle is sufficiently hindered to affect evaporation and growth. Despite numerous indirect inferences of viscous behavior from SOA evaporation or "bounce" within aerosol instruments, there have been no bulk measurements of the viscosity of well-constrained model aerosol systems of atmospheric significance.

Rate coefficients of C(1) and C(2) Criegee intermediate reactions with formic and acetic Acid near the collision limit: direct kinetics measurements and atmospheric implications.

Rate coefficients are directly determined for the reactions of the Criegee intermediates (CI) CH2 OO and CH3 CHOO with the two simplest carboxylic acids, formic acid (HCOOH) and acetic acid (CH3 COOH), employing two complementary techniques: multiplexed photoionization mass spectrometry and cavity-enhanced broadband ultraviolet absorption spectroscopy. The measured rate coefficients are in excess of 1×10(-10)  cm(3)  s(-1) , several orders of magnitude larger than those suggested from many previous alkene ozonolysis experiments and assumed in atmospheric modeling studies. These results suggest that the reaction with carboxylic acids is a substantially more important loss process for CIs than is presently assumed.