Photoelectron spectrum 1.3- butadiene

FIGURE 31. He(I) photoelectron spectrum of 1,3-butadiene (upper figure) and photoelectron/photoion coincidence spectra of various fragment ions. The yield of ion is indicated on the scale 0 to 1.0 °... 

Photoelectron.—n-Orbital energies appear to be unsuitable to discern the aromatic nature of phospholes (120) due to combined nn and ttn interactions. It is concluded that n conjugative and P-Cw hyperconjugative interactions stabilize the phos-phole system relative to the interrupted cw-butadiene and phosphorus subunits, and that the p.e. spectrum can be interpreted in favour of an aromatic phosphole ring.143 Other workers have discussed144 and reviewed145 this aromaticity problem, and there has been a quantum-chemical study of the aromatic nature of phosphorus hetero-cycles.144 The p.e. spectrum of the ylide (121) contains peaks at 6.19, 8.32, and... 

Photoelectron (PE) spectra have been measured for several (s-cis-diene)zirconocenes (5g, 51, 5s), for one example of the hafnium analogue (5n), and for (s-t/-ans-i7 -butadiene)Zr(C5Me5)2 (3c) (54). For both Cp and Cp series the highest occupied molecular orbital (HOMO) is separated from subsequent molecular orbitals (MO s) by a substantial energy difference. The observed PE spectra of 5 each exhibit a band around 6-6.5 eV (oi), well separated from several overlapping bands at 8-9 eV (6], f>2, fl2> bi). The PE spectrum of 3c shows a similar pattern [5.9 eV (aj) 7.1, 7.5, 7.5, 8.3 eV (fl2, i)]- The PE bands are in good accord with the... 

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