Analytical Photoion Spectros-copy Applied to Dissociative Single and Double Photoionization of Diatomic Molecules (H2, N2, O2, CO, and NO)
Abstract
This work reports the principle, advantage, and limitations of analytical photoion spectroscopy which has been applied to dissociative photoionization processes for diatomic molecules such as H2, N2, CO, and NO. Characteristic features observed in the differential photoion spectra are summarized with a focus on (pre)dissociation of (i) multielectron excitation states commonly observed in the inner valence regions, (ii) shape resonances, and (iii) doubly charged parent ions. Possible origins for negative peaks in the differential spectra are discussed. This spectroscopy is applied to the reported photoion branching ratios for D2 (and H2 at high energies). The main findings are as follows: ( 1) The direct dissociation of the X 2Σ{g/+} (1 sσ g ) state of D{2/+}, the two-electron excited state1Σ{/u +} (2 pσ u 2 sσ g ) of D2, and the2Σ{/u +} (2 pσ u ) state of D{2/+} appear clearly in the differential spectrum, as previously observed for H2. ( 2) Decay of H{2/+} (D{2/+}) to H+ (D+) above 38 eV is due to the direct dissociation of highly excited states of H{2/+} (D{2/+}) such as the2Σ{/g +} (2 sσ g ) and high-lying Rydberg states converging on H{2/2+} (D{2/2+}). ( 3) In the ionization continuum of H{2/2+} (D{2/2+}) peculiar dissociation pathways are observed. The differential photoion spectra for O2 derived from the reported photoion branching ratios are also presented. The (pre)dissociation of the b 4Σ{/g -}, B 2Σ{/g -}, III2Π u ,2Σ{/u -}, and2,4Σ{/g -} states of O{2/+} appears as the corresponding positive values in the spectra in accord with previous observations. Some other dissociation pathways possibly contributing to the spectra are discussed including dissociative double ionization.
- Publication:
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Zeitschrift fur Physik D Atoms Molecules Clusters
- Pub Date:
- March 1986
- DOI:
- 10.1007/BF01432497
- Bibcode:
- 1986ZPhyD...4...43M
- Keywords:
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- 38.80 E