The methylbenzenes vis-a-vis benzene. Comparison of their spectra in the Rydberg series region

Absolute extinction coefficient spectra of nine gaseous methylbenzenes (toluene, o-, m-, and p-xylene, 1,2,4- and 1,3,5-trimethylbenzene, 2,3,5,6-tetramethylbenzene, pentamethylbenzene, and hexamethylbenzene) have been recorded with a moderate resolution of 2.5 Å in the region of the Rydberg excitations below the first I.P. Term values, quantum defects, and ionization potentials have also been determined for each Rydberg series. Comparison with the benzene spectrum shows the importance of s-type Rydberg series in the spectra of these compounds.