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Photoelectron spectroscopy of the oxygen dimer and clusters
Author(s) -
Carnovale Frank,
Peel J. Barrie,
Rothwell Richard G.
Publication year - 1991
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210260406
Subject(s) - dimer , x ray photoelectron spectroscopy , ionization , photoemission spectroscopy , van der waals force , chemistry , ion , ionization energy , spectral line , atomic physics , molecule , nuclear magnetic resonance , physics , organic chemistry , astronomy
The He I photoelectron spectra of gas‐phase oxygen dimer and oxygen clusters have been measured in a pulsed beam. The spectrum of the dimer (O 2 ) 2 is characterized by broad bands which show 1:1 correspondence with those of the monomer O 2 . The vertical ionization energies are 0.2 ± 0.1 eV lower than those of the monomer. The photoelectron bands observed for mixtures of small clusters are identical to the dimer bands except for further shifts of up to ∼0.3 eV to lower ionization energies. The clusters spectra show bandwidths and bandshapes which are effectively the same as those measured for thin films of condensed O 2 , indicating that the oxygen dimer (O 2 ) 2 is the ionization chromophore in each case. This supports the dimer‐ion hypothesis proposed for the ionization of van der Waals clusters of closed‐shell molecules. Ab initio calculations on (O 2 ) 2 + show good agreement with the experimental data, and suggest that the ground dimer‐ion electronic state is of rectangular rather than trans ‐planar geometry.