Excited states and thermalization distances of photoelectrons created by VUV photoionization of pure liquid alkanes

Excited states probably occur at an intermediate stage in the vacuum ultraviolet ionization process of liquid alkanes. These states have been detected in the VUV photoionization spectra of cyclohexane and 2-2-dimethylbutane (DMB). Some of the discernible peaks of cyclohexane can be assigned as belonging to the Rydberg series observed in the gas phase. The spectral structures of liquid (photoionization) and gaseous (absorption) DMB are also comparable. The ionization quantum yield and thermalization range parameter of DMB were determined up to 2 eV above the ionization threshold of liquid DMB. Comparison with the values of the same parameters when quenchers are present seems to indicate that quenchers interact more with the excited states than with epithermal electrons