Absolute measurements of photoabsorption, Photoionization, and photodissociation cross sections of SiH4 and Si2H6 in the 13–22 eV region

The absolute values of the photoabsorption cross sections and photoionization quantum yields of silane and disilane have been measured in the 13–22 eV region. Using these values, we have evaluated the absolute cross sections of the photoionization and neutral dissociation. The individual structures observed in the cross section spectra have been interpreted in terms of the characters of superexcited states with strong emphasis on the neutral dissociation. The 3a1−1σ*(t2) state of silane presenting a broad peak at around 14.6 eV in an absorption cross section is shown to be strongly dissociative, whereas Rydberg series to the (3a1)−1 limit showing up vibrational structures between 16 and 18 eV predominantly undergo fast autoionization decay. A general importance of competition between autoionization and neutral dissociation is indicated of disilane in much higher energy region than the first ionization potential.