NATURE OF LOW-LYING ELECTRON EXCITED-STATES OF CYCLOPENTADIENYL)(ETA(7)-CYCLOHEPTATRIENYL)NIOBIUM

Electron absorption spectra of (eta(5)-cyclopentadienyl) (eta(7)-cyclo heptatrienyl)niobium in solution and in the vapor phase have been meas ured for the first time. possible variants of the band assignment for the spectrum of the complex in a solution have been considered. In the spectrum of the vaporous compound the bands at 29570, 31730, and 3463 0 cm(-1) correspond to the electron transitions from the 4d(sigma(+)) orbital to the lowest Rydberg p- and d-levels. The values of Rydberg t ransition terms and symmetry of p-states have been determined.