CO is an important component in many N 2 /CH 4 atmospheres including Titan, Triton, and Pluto, and has also been detected in the atmosphere of a number of exoplanets. Numerous experimental simulations have been carried out in the laboratory to understand the chemistry in N 2 /CH 4 atmospheres, but very few simulations have included CO in the initial gas mixtures. The effect of CO on the chemistry occurring in these atmospheres is still poorly understood. We have investigated the effect of CO on both gas and solid phase chemistry in a series of planetary atmosphere simulation experiments using gas mixtures of CO, CH 4 , and N 2 with a range of CO mixing ratios from 0.05% to 5% at low temperature (~100 K). We find that CO affects the gas phase chemistry, the density, and the composition of the solids. Specifically, with the increase of CO in the initial gases, there is less H 2 but more H 2 O, HCN, C 2 H 5 N/HCNO and CO 2 produced in the gas phase, while the density, oxygen content, and degree of unsaturation of the solids increase. The results indicate that CO has an important impact on the chemistry occurring in our experiments and accordingly in planetary atmospheres.

Vibronic spectra of doublet-doublet transitions of 1-hydronaphthyl (1HN), 2-hydronaphthyl (2HN), and 1,2,3-trihydronaphthyl (THN, tetralyl) radicals have been recorded under jet-cooled conditions. Transitions due to the two C(10)H(9) isomers were identified and assigned based on the choice of radical precursor, visible-visible hole-burning spectroscopy, comparison of observed vibronic transitions with calculation, and photoionization efficiency scans. The latter provided accurate ionization potentials for the three free radicals (IP(1HN) = 6.570 eV, IP(2HN) = 6.487 eV, IP(THN) = 6.620 eV, errors +/-0.002 eV). A thermochemical cycle is used to extract from these ionization potentials the C-H bond dissociation energy (BDE) of 1HN at the 1-position of 121.2 +/- 2 kJ/mol. Using proton affinities of 2HN and THN calculated at the G3(MP2, CC)//B3LYP/6-311G** level of theory, the corresponding C-H BDEs of 2HN at the 2-carbon (103.6 +/- 2 kJ/mol) and of THN at the 3-position (168 +/- 3 kJ/mol) are derived. The possible role played by these hydronaphthyl radicals in Titan's atmosphere, the interstellar medium, and combustion are briefly discussed.

Very little experimental work has been done to explore the properties of photochemical hazes formed in atmospheres with very different compositions or temperatures than those of the outer solar system or of early Earth. With extrasolar planet discoveries now numbering thousands, this untapped phase space merits exploration. This study presents measured chemical properties of haze particles produced in laboratory analogs of exoplanet atmospheres. We used very high-resolution mass spectrometry to measure the chemical components of solid particles produced in atmospheric chamber experiments. Many complex molecular species with general chemical formulas C w H x N y O z were detected. We detect molecular formulas of prebiotic interest in the data, including those for the monosaccharide glyceraldehyde, a variety of amino acids and nucleotide bases, and several sugar derivatives. Additionally, the experimental exoplanetary haze analogs exhibit diverse solubility characteristics, which provide insight into the possibility of further chemical or physical alteration of photochemical hazes in super-Earth and mini-Neptune atmospheres. These exoplanet analog particles can help us better understand chemical atmospheric processes and suggest a possible source of in situ atmospheric prebiotic chemistry on distant worlds.

Laboratory investigations of the isomer-specific spectroscopy of several C10Hn isomers with n = 8-12 are described, focusing on structures of relevance to the formation or subsequent reaction of naphthalene. The photochemical models of Titan's atmosphere have now progressed to the point that further development of the large-molecule end of the model must recognize and explicitly incorporate the unique spectroscopy, photochemistry, and reactivity of structural isomers. Mass-resolved, resonant two-photon ionization (R2PI) was used to record ultraviolet spectra of specific C10Hn composition, while hole-burning methods were used to resolve the spectra of different structural and conformational isomers under jet-cooled conditions. The R2PI spectrum of a new C10H8 isomer, 1-phenyl-1-butyne-3-ene, is described and contrasted with other C10H8 isomers. The anticipated role for resonance-stabilized radicals is illustrated by studies of the visible spectroscopy of two hydronaphthyl radical isomers, 1-C10H9 and 2-C10H9, and the trihydronaphthyl radical 1,2,3-C10H11. Conformation-specific spectra of an anticipated C10H12 recombination product of benzyl and allyl radicals is also reported. A reaction scheme that fleshes out the experimental data surrounding naphthalene and its hydrogenated radicals and ions is proposed as a basis for future modeling under Titan's conditions.