RENNER-TELLER EFFECT AND RYDBERG-VALENCE MIXING IN THE N AND O K-EDGE PHOTOABSORPTION SPECTRA OF N2O

We have measured high-resolution angle-resolved ion-yield spectra of the O and N 1s excited N2O molecules (Nt-Nc-O) and investigated them with the help of ab initio quantum chemical calculations. The peak width of the Nc 1s→π* transition is larger than that of the Nt 1s →π* one. This mainly arises from different populations of bending vibrations excited through the Renner-Teller effect, which breaks the degeneracy of the 1s→πz.ast; excited states by bending the linear molecule. The angular distribution of fragment ions emitted after the Auger decay is also affected by the Renner-Teller effect. That is, fragment ions significantly lose the information of the Π symmetry of the linear molecule. For the 1s→Rydberg excitations no Renner-Teller effect is observed and the angular distribution is directly related to the Σ and Π symmetries. Furthermore, it is found that the peak intensities of the O and Nt 1s→ns σ Rydberg transitions are unusually large. The N2O molecule has two σ* orbitals, σs*(8σ) and σp*(9σ), below and above the ionization threshold and the 1s→σs* excited states are mixed with the O and Nt 1s-nsσ Rydberg excited states; on the other hand, the Nc 1s→σs* transition is almost dipole-forbidden because of the orbital symmetry. © 1995 American Institute of Physics.