Photoisomerization and Infrared Spectra of Allene and Propyne Cations in Solid Argon

Allene and propyne as well as their cationic forms play important roles in combustion and interstellar chemistry and serve as a model system for molecular spectroscopic studies. Both cations show Jahn–Teller (J–T) distortions in their ground states. These J–T distortions make the theoretical and experimental studies of their electronic structures difficult. We produced allene cations upon electron bombardment during matrix deposition of Ar containing a small proportion of allene. The intensities of the absorption features of the allene cation decreased after irradiation with UV light, whereas new bands attributed to propyne cations increased. The observed line wavenumbers, relative intensities, and deuterium-substituted isotopic ratios of the isomers of C₃H₄⁺ agree satisfactorily with those predicted by density functional theory at the B3PW91/aug-cc-pVTZ level of theory. This method produced the hydrocarbon cations of interest with few other fragments that enabled the clear identification of the IR spectra of allene and propyne cations

Study on the Adsorption and Reactions of FCH₂CH₂OH and ClCH₂CH₂OH on Ni(111): Effects of Halogen and Preadsorbed Oxygen

Temperature-programmed reaction/desorption (TPR/D), reflection–absorption infrared spectroscopy (RAIRS), and X-ray photoelectron spectroscopy (XPS) have been employed to investigate the reactions of FCH₂CH₂OH and ClCH₂CH₂OH on Ni(111) and oxygen-precovered Ni(111) (O/Ni(111)). In the chemical process of FCH₂CH₂OH on Ni(111), only FCH₂CH₂O- is found to be the stable reaction intermediate, which starts to appear at ∼190 K. At low coverages, this intermediate decomposes into H₂ and CO. Additional C₂H₄ (219 K) is generated at higher exposures. On Ni(111) at 200 K, ClCH₂CH₂OH mainly dissociates to form ClCH₂CH₂O- and -CH₂CH₂O- at lower exposures, with H₂ and CO as the final products, while ClCH₂CH₂O- becomes predominant at higher exposures and is responsible for the extra C₂H₄ channel of 218 K. C₂H₄ is also generated at 161 and 174 K as the exposure is increased to render multilayer adsorption. Due to the competition in the scission of the carbon–halogen and carbon–hydrogen bonds, ClCH₂CH₂OH has better reactivity toward C₂H₄ formation than FCH₂CH₂OH. No -CH₂CH₂OH is found in the decomposition of FCH₂CH₂OH and ClCH₂CH₂OH on Ni(111), which is the intermediate in the reaction of ICH₂CH₂OH on Ni(100) and Pd(111). The presence of preadsorbed oxygen can enhance the ethylene formation at low coverages of FCH₂CH₂OH and ClCH₂CH₂OH. At higher coverages, additional acetaldehyde is formed in the reaction of FCH₂CH₂OH, in contrast to the ethylene oxide from ClCH₂CH₂OH

Study on the Adsorption and Reactions of FCH₂CH₂OH and ClCH₂CH₂OH on Ni(111): Effects of Halogen and Preadsorbed Oxygen

Temperature-programmed reaction/desorption (TPR/D), reflection–absorption infrared spectroscopy (RAIRS), and X-ray photoelectron spectroscopy (XPS) have been employed to investigate the reactions of FCH₂CH₂OH and ClCH₂CH₂OH on Ni(111) and oxygen-precovered Ni(111) (O/Ni(111)). In the chemical process of FCH₂CH₂OH on Ni(111), only FCH₂CH₂O- is found to be the stable reaction intermediate, which starts to appear at ∼190 K. At low coverages, this intermediate decomposes into H₂ and CO. Additional C₂H₄ (219 K) is generated at higher exposures. On Ni(111) at 200 K, ClCH₂CH₂OH mainly dissociates to form ClCH₂CH₂O- and -CH₂CH₂O- at lower exposures, with H₂ and CO as the final products, while ClCH₂CH₂O- becomes predominant at higher exposures and is responsible for the extra C₂H₄ channel of 218 K. C₂H₄ is also generated at 161 and 174 K as the exposure is increased to render multilayer adsorption. Due to the competition in the scission of the carbon–halogen and carbon–hydrogen bonds, ClCH₂CH₂OH has better reactivity toward C₂H₄ formation than FCH₂CH₂OH. No -CH₂CH₂OH is found in the decomposition of FCH₂CH₂OH and ClCH₂CH₂OH on Ni(111), which is the intermediate in the reaction of ICH₂CH₂OH on Ni(100) and Pd(111). The presence of preadsorbed oxygen can enhance the ethylene formation at low coverages of FCH₂CH₂OH and ClCH₂CH₂OH. At higher coverages, additional acetaldehyde is formed in the reaction of FCH₂CH₂OH, in contrast to the ethylene oxide from ClCH₂CH₂OH