HeI ultraviolet photoelectron spectra (UPS) of N-(2-bromo-ethy) carbazole and N-ethenylcarbazole are recorded for the first time. Using the configuration optimized at RHF/6-31G level,the SCF MO calculations of the two compounds are carried out at RHF/6-31^* level. The UPS of the two compounds are assigned and the electronic structures are discussed based on the SCF MO calculations, contrasting with the ionziation potentials (IPs) changing rules of carbazole and N - alkylcarbazole. The result shows that the UPS of N - (2-bromo- ethyl) carbazole exists two lone - pair ionization bands of Br atom at 10.295, 10.540eV, which is different from that of N-alkylcarbazole. The special IPs changing rules of N-ethenylcarbazole compared with carbazole show that the molecule is almost planar.

Key words: CARBAZOLE P, ELECTRONIC STRUCTURE, ULTRAVIOLET SPECTROPHOTOMETRY, GEOMETRICAL ISOMERISM, MOLECULAR ORBITAL THEORY, BROMINE COMPOUNDS, ETHYLENE P