The absorption spectra of benzene derivatives in the vacuum ultraviolet.

New photographs of the far ultra-violet spectrum of benzene are presented. The absorption from 2000 to 1800A (Amlx, c. 1980A) is regarded not as a part of the much stronger absorp­ tion of peak at 1790 A but as due to a separate transition. Sharp bands lying at 1790 A represent the first member of a previously reported Rydberg series. The spectra of toluene, xylene, monochloroando-dichlorobenzene,bromobenzene, iodobenzene and pyridine are briefly described, and the shifts relative to benzene are discussed. T?wo Rydberg series were observed for toluene, converging to a first ionization potential of 8-77 ± 0-05 V.