Ion-pair formation from saturated hydrocarbons through photoexcitation of an inner-valence electron

Publisher Website
Google Scholar
Abstract
Ion‐pair formation from the superexcited states of saturated hydrocarbons has been studied by negative‐ion mass spectrometry using synchrotron radiation in the 15–35 eV photon energy range. Negative ion H− has been observed from CH4, C2H6, C3H8, n‐C4H10, iso‐C4H10, and neo‐C5H12. The maximum cross section ranges from 1.6×10−21 to 1.0×10−20 cm2. Strong peaks observed in the photodissociation efficiency curve of H− are assigned as resulting from transitions to the Rydberg states formed by promotion of an electron in a carbon 2s‐type molecular orbital. In contrast, the valence‐Rydberg transitions from a carbon 2p‐type orbital have little (C2H6) or no contribution [CH4 and C m H2m+2 (3≤m≤5)] to the H− formation. This difference can be interpreted as that the latter Rydberg states have short lifetime with respect to autoionization to lower ionic states on account of relatively large overlap between two carbon 2p‐type orbitals involved in an electron exchange process.

This publication has 41 references indexed in Scilit: