No Access Submitted: 18 May 1998 Accepted: 14 August 1998 Published Online: 16 November 1998
J. Chem. Phys. 109, 8426 (1998);
more...View Affiliations
  • Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
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  • C. A. Fancher
  • H. L. de Clercq
  • O. C. Thomas
  • D. W. Robinson
  • K. H. Bowen
We have recorded, assigned, and analyzed the photoelectron spectrum of ZnO. The adiabatic electron affinity (E.A.a) of ZnO and the vibrational frequencies of both ZnO and ZnO were determined directly from the spectrum, with a Franck–Condon analysis of its vibrational profile providing additional refinements to these parameters along with structural information. As a result, we found that E.A.a(ZnO)=2.088±0.010 eV, ωe(ZnO)=805±40 cm−1, ωe(ZnO)=625±40 cm−1, and that re(ZnO)>re(ZnO) by 0.07 Å. Since our measured value of E.A.a(ZnO) is 0.63 eV larger than the literature value of E.A.(O), it was also evident, through a thermochemical cycle, that D0(ZnO)>D0(ZnO) by 0.63 eV. This, together with the literature value of D0(ZnO), gives a value for D0(ZnO) of 2.24 eV. Since the extra electron in ZnO is expected to occupy an antibonding orbital, the combination of D0(ZnO)>D0(ZnO), ωe(ZnO)<ωe(ZnO), and re(ZnO)>re(ZnO) was initially puzzling. An explanation was provided by the calculations of Bauschlicher and Partridge, which are presented in the accompanying paper. Their work showed that our experimental findings can be understood in terms of the a 3Π state of ZnO dissociating to its ground-state atoms, while the X 1Σ+ state of ZnO formally dissociates to a higher energy atomic asymptote.
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