53, ionization potential vibrational spectrum

Fig. 9a, b. A portion of a photoelectron spectrum (idealized) showing (a) the identification of adiabatic and vertical ionization potentials with resolved (1) and unresolved (2) vibrational structures, (b) the identification of a higher adiabatic ionization potential with a break . 

Despite the calculated, rather low first ionization potential, suggesting an isolated, easy-to-detect band in the silaethene PE spectrum, numerous pyrolysis experiments with promising precursors, such as 1,3-disilacyclobutane, yielded no reproducible PE band in the expected region. Eventually, in the thermal retrodiene cleavage of a 5,6-bis(trifluoromethyl) derivative of 2-silabicyclo[2.2.2]octa-5,7-diene, a novel band exhibiting vibrational fine structure appeared within the precalculated region (Figure 4). 

The first ionization potential of ethane was measured by photoionization techniques more than 30 years ago [56-62] and it was found to be between 11.4 and 11.65 eV. Some indication of vibrational fine structure was found by Chupka and Berkowitz [62]. The classic Hel photoelectron spectrum of ethane was recorded by liirner s group (Baker et al. [25, 57] it is reproduced on Figure 3. 

---