The dynamics of the photoionization of the two outermost orbitals of C(60) has been studied in the oscillatory regime from threshold to the carbon K edge. We show that geometrical properties of the fullerene electronic hull, such as its diameter and thickness, are contained in the partial photoionization cross sections by examining ratios of partial cross sections as a function of the photon wave number in the Fourier conjugated space. Evaluated in this unconventional manner photoemission data reveal directly the desired spatial information.
Because of inversion symmetry and particle exchange, all constituents of homonuclear diatomic molecules are in a quantum mechanically non-local coherent state; this includes the nuclei and deep-lying core electrons. Hence, the molecular photoemission can be regarded as a natural double-slit experiment: coherent electron emission originates from two identical sites, and should give rise to characteristic interference patterns. However, the quantum coherence is obscured if the two possible symmetry states of the electronic wavefunction ('gerade' and 'ungerade') are degenerate; the sum of the two exactly resembles the distinguishable, incoherent emission from two localized core sites. Here we observe the coherence of core electrons in N(2) through a direct measurement of the interference exhibited in their emission. We also explore the gradual transition to a symmetry-broken system of localized electrons by comparing different isotope-substituted species--a phenomenon analogous to the acquisition of partial 'which-way' information in macroscopic double-slit experiments.
The 3d photoelectron spectrum of xenon has been measured at several photon energies in the immediate threshold region. The absolute photoionization cross section and angular anisotropy parameter  have been determined for the two spin-orbit-split components. The experimental results are compared with calculations using a relaxed single-channel approximation. In agreement with theory, most abrupt changes in cross section and angular distribution are observed just above threshold. However, the Xe 3d 5/2 photoionization cross section also reveals, some 30-eV above threshold a second maximum that has not been predicted theoretically.
For emission out of the molecule along the molecular axis, the direct wave interferes with an electron wave that is scattered an odd number of times and dominated by singlescattering (66% back-scattering), whereas for emission into the molecule, the direct
Angular distributions of C͑1s͒ photoelectrons emitted from oriented CO molecules were measured using a new method: mass and angle-resolved photoelectron-photoion coincidence spectroscopy. Along with the angular momentum composition of the photoelectron wave, the experiment reveals pronounced forward-backward asymmetries in the photoemission intensity with respect to the molecular orientation. This asymmetry, being observed for the first time in molecular photoionization, is interpreted in terms of multiple scattering effects. Calculations using the MS-Xa method show good quantitative agreement with the presented experimental results. [S0031-9007(97)04163-X]
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