The planet Venus exhibits atmospheric absorption in the 320–400 nm wavelength range produced by unknown chemistry. We investigate electronic transitions in molecules that may exist in the atmosphere of Venus. We identify two different S2O2 isomers, cis‐OSSO and trans‐OSSO, which are formed in significant amounts and are removed predominantly by near‐UV photolysis. We estimate the rate of photolysis of cis‐ and trans‐OSSO in the Venusian atmosphere and find that they are good candidates to explain the enigmatic 320–400 nm near‐UV absorption. Between 58 and 70 km, the calculated OSSO concentrations are similar to those of sulfur monoxide (SO), generally thought to be the second most abundant sulfur oxide on Venus.

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The reaction of electronically excited triplet state sulfur dioxide (SO) with water was investigated both theoretically and experimentally. The quantum chemical calculations find that the reaction leads to the formation of hydroxyl radical (OH) and hydroxysulfinyl radical (HOSO) via a low energy barrier pathway. Experimentally the formation of OH was monitored via its reaction with methane, which itself is relatively unreactive with SO, making it a suitable probe of OH production from the reaction of SO and water. This reaction has implications for the formation of OH in environments that are assumed to be depleted in OH, such as volcanic plumes. This reaction also provides a mechanism for the formation of OH in planetary atmospheres with little or no oxygen (O) or ozone (O) present.

We have investigated the effects of substituents on the properties of the dihydroazulene/vinylheptafulvene photoswitch. The focus is on the changes of the thermochemical properties by placing electron withdrawing and donating groups on the monocyano and dicyano structures of the parent dihydroazulene and vinylheptafulvene compounds. We wish to increase the energy storage capacity, that is, the energy difference between the dihydroazulene and vinylheptafulvene isomers, of the photoswitch by computational molecular design and have performed over 9000 electronic structure calculations using density functional theory. Based on these calculations, we obtain design rules for how to increase the energy storage capacity of the photoswitch. Furthermore, we have investigated how the activation energy for the thermally induced vinylheptafulvene to dihydroazulene conversion depends on the substitution pattern, and based on these results, we have outlined molecular design considerations for obtaining new desired target structures exhibiting long energy storage times. Selected candidate systems have also been investigated in terms of optical properties to elucidate how sensitive the absorption maxima are to the functionalizations.

The conformer-specific reactivity of gas-phase pyruvic acid following the S1(nπ*) ← S0 excitation at λmax = 350 nm (290–380 nm) and the effect of water are investigated for the two lowest energy conformers. Conformer-specific gas-phase pyruvic acid photolysis rate constants and their respective populations are measured by monitoring their distinct vibrational OH-stretching frequencies. The geometry, relative energies, fundamental vibrational frequencies, and electronic transitions of the pyruvic acid conformers and their monohydrated complexes are calculated with density functional theory and ab initio methods. Results from experiment and theory show that the more stable conformer with an intramolecular hydrogen bond dominates the gas-phase photolysis of pyruvic acid. Water greatly affects the gas-phase pyruvic acid conformer population and photochemistry through hydrogen bonding interactions. The addition of water decreases the gas-phase relative population of the more stable conformer and decreases the molecule’s gas-phase photolysis rate constants. The theoretical results show that even a single water molecule interrupts the intramolecular hydrogen bond, which is essential for the efficient photodissociation of gas-phase pyruvic acid. Results of this study suggest that the aqueous-phase photochemistry of pyruvic acid proceeds through hydrogen-bonded conformers lacking an intramolecular hydrogen bond.