In the research reported in this dissertation, experiments were designed and performed to investigate the interactions of atmospheric gases with high-energy photons and/or electrons, which can produce highly reactive ions and radicals via ionization and dissociation, and which in turn may result in previously unexplored isotope effects or in formation of aerosols with optical properties that are difficult to predict and measure. Knowledge of both isotope effects and the optical properties of aerosols formed by UV photolysis of precursor gases are highly relevant for interpreting observations of and understanding chemical and physical processes occurring in a wide variety of planetary atmospheres. Here, photoionization efficiency spectra of isotopologues of N2 (14N2, 15N14N, and 15N2) and CO2 (12C16O2, 13C16O2, 12C16O18O, 13C16O18O, 12C18O2, and 13C18O2) using synchrotron radiation at the Advanced Light Source were measured, the polarization and intensity of laser light scattered by photochemically-generated aerosols suspended in the gas phase as a function of scattering angle were investigated in situ using a newly designed and built computer-controlled custom polarimeter, and the isotopic composition of N2O produced in a newly designed and constructed corona discharge apparatus was measured. Isotope effects in the photoionization of N2 and CO2 may be important in determining the isotopic composition in planetary atmospheres, such as those on Earth and Titan in the case of N2 and on Mars and Venus in the case of CO2, and provide new data to address uncertainties in spectral peak assignments in the photoionization spectra, and yet have not been previously measured. For example, for N2, the measured differences in photoinization efficiencies between 14N2 and 15N14N, may help resolve differences in the isotopic composition of N2 versus that for HCN observed on Titan. In addition, the spectral assignment for the feature at 15.677 eV in the 14N2 photoionization spectrum has remained controversial despite decades of research. The measured isotope shifts for this peak are compared with isotope shifts predicted using Herzberg equations for the isotopic differences in harmonic oscillator energy levels plus the first anharmonic correction for the three proposed assignments. The measured isotope shifts for this peak relative to 14N2 are 0.015 +/- 0.001 eV for 15N2 and 0.008 +/- 0.001 eV for 15N14N (reported here for the first time), which match most closely with the isotope shifts predicted for transitions to the (A 2-Pi-u v=2)4-s-sigma-g 1-Pi-u state of 0.0143 eV for 15N2 and 0.0071 eV for 15N14N, and thus assignment to this transition is favored. For CO2, the measured isotope effects in photoionization yield ratios of photoionization rate coefficients, J (i.e., photoionization cross-sections convolved with the solar spectrum and integrated over all photoionization energies), that are less than 1: J(13C16O2)/J(12C16O2) = 0.97 +/- 0.02, J(12C16O18O)/J(12C16O2) = 0.97 +/- 0.02, J(13C16O18O)/J(12C16O2) = 0.97 +/- 0.02, J(12C18O2)/J(12C16O2) = 0.99 +/- 0.02, and J(13C18O2)/J(12C16O2) = 0.98 +/- 0.02. These isotope effects in photoionization rate coefficients are likely large enough to contribute to (if not dominate) enrichments in 13C in CO2 in the martian atmosphere, which have largely been attributed to atmospheric escape over billions of years, and may also be important in the atmospheres of Venus and Earth, thus warranting inclusion in models of the isotopic composition of CO2 in planetary atmospheres. Aerosols generated by UV photolysis of precursor gases are present in a number of planetary atmospheres, including Titan, and most likely, early Earth and early Mars, and are expected to have a profound effect on atmospheric radiative transfer, yet the number of investigations of aerosol optical properties suspended in the gas phase is extremely limited. In order to measure the intensity and polarization state of light scattered by photochemically-generated aerosols as a function of scattering angle, a custom polarimeter consisting of a quarter-wave plate mounted in a computer-controlled rotating stage and a linear polarizer was designed and built. The polarimeter was placed into the 13 L reaction chamber to measure the intensity and polarization of light scattered by photochemically-generated aerosol in situ, and the parameters of the Stokes vector were calculated at a number of scattering angles. The results demonstrate that this technique can be used to measure the polarization and angular dependence (phase function) of light scattered by aerosol particles in situ while still suspended in the gas phase, with the ultimate goal of using these measurements to attain the size distribution and index of refraction of the aerosol particles for applications to radiative transfer in planetary atmospheres, such as early Earth and Titan. Measurements of the isotopic composition of N2O can be used to infer its sources and sinks, and understanding the isotopic composition of N2O formed by corona discharge in air (a process which can occur, for example, in thunderstorms) may be important for understanding atmospheric observations of N2O if the isotope effects in N2O formation are large. To measure the isotopic composition of N2O formed by corona discharge, a new apparatus was designed and built to produce N2O by corona discharge and isolate and collect the N2O cryogenically for subsequent analysis by continuous flow isotope ratio mass spectrometry. Results from the first measurements of isotopic composition (reported as delta-15 N, delta-18O, and the "site-specific" delta-15N values, delta-15N-alpha and delta-15N-beta) indicate that, under some conditions, the isotopic composition of N2O formed by corona discharge is significantly different from the reactant N2 and O2 and from background tropospheric N2O, although none of the measurements reported here show fractionations larger than 4% (i.e., 40 per mil) relative to the starting N2 or O2 or tropospheric N2O. Additional testing under other experimental conditions (e.g., pressure, discharge residence time, discharge current) is warranted to assess whether fractionations might be large enough to include in atmospheric models.

The ocean has absorbed a significant portion of all human-made carbon dioxide emissions. This benefits human society by moderating the rate of climate change, but also causes unprecedented changes to ocean chemistry. Carbon dioxide taken up by the ocean decreases the pH of the water and leads to a suite of chemical changes collectively known as ocean acidification. The long term consequences of ocean acidification are not known, but are expected to result in changes to many ecosystems and the services they provide to society. Ocean Acidification: A National Strategy to Meet the Challenges of a Changing Ocean reviews the current state of knowledge, explores gaps in understanding, and identifies several key findings. Like climate change, ocean acidification is a growing global problem that will intensify with continued CO2 emissions and has the potential to change marine ecosystems and affect benefits to society. The federal government has taken positive initial steps by developing a national ocean acidification program, but more information is needed to fully understand and address the threat that ocean acidification may pose to marine ecosystems and the services they provide. In addition, a global observation network of chemical and biological sensors is needed to monitor changes in ocean conditions attributable to acidification.

A multitude of processes that operate in the upper atmosphere are revealed by detailed physical and mathematical descriptions of the interactions of particles and radiation, temperatures, spectroscopy and dynamics.

Since 1948, this Series has filled the gap between the papers that report and the textbooks that teach in the diverse areas of catalysis research. The editors of and contributors to Advances in Catalysis are dedicated to recording progress in this area. Each volume of Advances in Catalysis contains articles covering a subject of broad interest.

This book is dedicated to studying the ocean with radar tools, in particular, with space radars. Being intended mainly for the scientists preoccupied with the problem (as well as senior course students), it concentrates and generalizes the knowledge scattered over specialized journals. The significant part of the book contains the results obtained by the author. - Systematically collects and describes the approaches used by different laboratories and institutions - Deals with the physics of radar imagery and specifically with ocean surface imagery - Useful for students and researchers specializing in the area of ocean remote sensing using airborne or space-borne radars, both SAR and RAR