Soft X-Ray-induced Dimerization of Methane

Abstract Carbon 1s excitation of methane, CH 4 , has been studied in the gas phase using ion trap integrated with photon–ion instrument at PETRA III/DESY and soft X-rays from beamline P04. The created photoions are stored within so that further steps can undergo reactions neutral methane molecules. ionic photoproducts as well reaction products thereby mass-over-charge analyzed by an time-of-flight spectrometer. Besides photoions, product ions up to three carbon atoms found. In contrast experiments vacuum ultraviolet radiation, especially highly reactive a small number hydrogen such C 2 mathvariant="normal">H + ${{\rm{C}}}_{2}{{\rm{H}}}_{3}^{+}$?> 3 found, which important precursors for larger hydrocarbons C 6 H . Possible production routes on basis model considers probabilities photofragmentation first subsequent chemical step. indicates high degree fragmentation photons energies around 280 eV is favoring these products. results measurements show like be generated single collision ionization methane. suggest might planetary atmospheres, usually not taken into account. However, due large cross sections involved, they have influence even when corresponding photon flux rather small.