A comparison between excited states detected through VUV photoionization and VUV photon absorption in dielectric liquids

Some characteristic energies are observed in the first derivative of the photoionization spectrum of tetramethyl silane (TMS), cyclopentane, cyclohexane and 2,2 dimethyl butane. They could correspond to "autoionizing" states situated above the ionization threshold. Here we examine if they can be fitted to possible Rydberg series. These observations are crossed with recent data of some authors having detected shoulders - and possible associated excited transitions - in the VUV absorption spectra of these non-polar liquids. Moreover the incidence of these excited states on molar extinction coefficients values obtained both by direct VUV absorption and by a photoionization way is examined.