| The protection and preservation of the Earth's atmosphere and the development of legislative standards to enforce this protection are only possible through a comprehensive understanding of the coupled dynamics and chemical reactivity of the atmosphere. In order for the modern environmental chemist to properly characterize and model the constituents of our atmosphere, and thus advise policy makers from an informed position, a quiver of analytical tools is necessary. Due to the dynamic nature of the atmosphere, these analytical tools must be capable of reliable and consistent in-situ detection of trace pollutants. This necessitates the development and use of portable or mobile techniques.; In this work the development and application of such analytical methods for the study of atmospherically important gaseous compounds is described. Two separate research projects in the field of laser ionization mass spectrometry (LI MS) are presented.; The first research project studies the detection of primary and secondary pollutants common to most urban and remote settings. This technique combines atmospheric pressure laser ionization (APLI) and time-of-flight (TOF) MS. Laser ionization of the target analyte is achieved via well-described resonant enhanced multi-photon ionization (REMPI) pathways using nanosecond pulse width lasers. The compounds studied include NOx as well as several aromatic compounds including benzene, toluene, 2,5-dicholorotoluene and x-, m-, and p-xylene. Nitric oxide is monitored using two color REMPI scheme and provided a detection limit of 0.7 pptv with a 20 second integration time. Nitrogen dioxide is monitored using a novel two color double resonant REMPI scheme and a measured detection limit of 5 pptv are reported. All organics are measured using a two color REMPI scheme and typical detection limits of 15 pptv is reported. These findings represent the first successful results obtained using broad bandwidth laser radiation and the REMPI APLI MS approach.; The second research project studies the applicability of APLI MS in the detection of highly reactive photolabile species. Picosecond pulse width lasers are combined with the APLI MS technique to provide a direct method with which to study these species. Fast laser pulses make LI techniques available to study photolabile molecules such as nitrogen dioxide. Parent ion production of nitrogen dioxide in the wavelength range 450 to 550 nm and the corresponding second harmonic range is described with a maximum NO2+/NO + ratio of 12% is observed at 490 nm. |
