C. R. Brundle

High‐Resolution He i and He ii Photoelectron Spectra of Xenon Difluoride

The vertical I.P.s of the first eight ionizations in the XeF2 molecule have been determined, and they compare favorably with the results of Gaussian‐type orbital calculations. The first two ionic states of XeF2 are the 2Π3/2 (12.42 eV) and 2Π1/2 (12.89 eV) spin–orbit components formed by ionization from the highest‐filled π orbital (5πu). As judged by the vibronic structure of the transitions, the two upper states are linear, with Xe–F distances very much like those of the ground state. The fifth (15.60 eV) and sixth (16.00 eV) I.P.s similarly involve the ejection of an electron from the 4πu orbitals, and thus they are separated by the action of spin–orbit coupling. Substitution of He ii α excitation (40.82 eV) for the He i α excitation (21.21 eV) results in both the additional ionization of electrons from the 9σg molecular orbital (22.5 eV), and a drastic change in the relative intensities of certain peaks in the lower I.P. region. Rydberg bands in the optical spectrum of XeF2 can be correlated with th...

Photoelectron Spectra of Small Rings. IV. The Unsaturated Three‐Membered Rings

The HeI and HeII photoelectron spectra of cyclopropene, diazirine, and difluorodiazirine are compared with the results of Gaussian orbital calculations of double‐zeta quality. The generally excellent agreement between calculation and experiment strongly supports the theoretically derived inversions of many of the levels. For example, on going from cyclopropane to cyclopropene, there is a crossover of the uppermost pi and sigma MOs, which again recross to place sigma above pi in diazirine and difluorodiazirine. In the diazirines, the lone pair splitting is 3.5 eV, with the uppermost pi MO located between them. Several accidental degeneracies occur in difluorodiazirine.

Hei and Heii Photoelectron Spectra and the Electronic Structures of XeF2, XeF4, and XeF6

The high‐resolution photoelectron spectra of XeF2, XeF4, and XeF6 have been obtained essentially free from any impurity features, and the ionization potentials up to 28 eV have been measured. The results are used, in conjunction with recent ab initio calculations, to assign the molecular orbital electronic structure of these molecules. Agreement between experiment and calculation is fairly good.

The electronic structure and the optical and photoelectron spectra of carbon subsulfide

Carbon subsulfide, the linear molecule S=C=C=C=S, has been investigated by self‐consistent field‐Xα‐scattered wave calculations (overlapping spheres), optical (650–230 nm), and photoelectron [He(I) and He(II)] spectroscopy. The ground state valence level electronic configuration is found to be (6σ+g)2(5σ+u)2(7σ+g)2(6σ+ u)2 (7σ+u)2(8σ+g)2(2πu)4(2πg)4(3πu)4. Comparison of the photoelectron band positions with the calculated ionization potentials, and analysis of their vibrational structure, allows assignments to be made. The experimental ionization potentials (ev) are 3πu(9.09), 2πg(11.24), 2πu(12.87), 8σ+g(14.47), 7σ+u(14.87), 6σ+u(18.2), 7σ+g(19.3), 5σ+u(20.5), 6σ+g(21.9). Agreement between calculated and experimental ionization potentials is very good for the π levels, fair for the 8σ+g and 7σ+u levels and poor for the remaining (low lying) σ levels, although the splittings between the low lying σ levels are correctly calculated. There are two principle features in the optical spectrum, a weak band at 20...