The electronic structures of methane, ethane, ethylene and formaldehyde studied by high-resolution molecular photoelectron spectroscopy

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We have obtained the photoelectron spectra of the compounds in the title using the 584 Å radiation (hν = 21.21 eV) and a high-resolution electron velocity analyser. The results for methane indicate the presence of only one occupied orbital ( pt 2) 6 in the accessible energy range. There is some indication of vibrational fine structure but no detailed analysis is possible and there is some indication that Jahn—Teller splitting may be important. Similar effects are noted in ethane where four orbital levels are found. In both ethylene and formaldehyde extensive vibrational fine structure is found for most of the ionic states and has been interpreted with the assistance of data for the deuterated compounds in terms of the molecular orbitals indicated by the theoretical calculations of earlier workers.