| 1. |
- Liu, X. J., et al.
(författare)
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Young's double-slit experiment using core-level photoemission from N-2 : revisiting Cohen-Fano's two-centre interference phenomenon
- 2006
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 39:23, s. 4801-4817
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Tidskriftsartikel (refereegranskat)abstract
- The core-level photoelectron spectra of N-2 molecules are observed at high energy resolution, resolving the 1 sigma(g) and 1 sigma(u) components as well as the vibrational components in the extended energy region from the threshold up to 1 keV. The sigma(g)/sigma(u) cross section ratios display modulation as a function of photoelectron momentum due to the two-centre interference, analogous to the classical Young's double-slit experiment, as predicted by Cohen and Fano a long time ago. The Cohen-Fano interference modulations display different phases depending on the vibrational excitations in the core-ionized state. Extensive ab initio calculations have been performed within the Hartree-Fock and random phase approximations in prolate spheroidal coordinates. The dependence of photoionization amplitudes on the vibrational states was taken into account using the Born-Oppenheimer approximation. The ab initio results are in reasonable agreement with the experimental data. The theoretical analysis allows the modulation to be connected with the onset of transitions to the states of increasing orbital angular momentum which occurs at increasing photon energies. Deviation from the Cohen-Fano formula is found for both the experimental and the ab initio results and is attributed to electron scattering by the neighbouring atom. A new formula for the interference modulation is derived within the framework of the multiple scattering technique. It differs from the classical Cohen-Fano formula by the addition of twice the scattering phase of the photoelectron by the neighbouring atom. We demonstrate that one can measure directly the scattering phase by fitting our formula to the experimental results.
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| 2. |
- Semenov, S. K., et al.
(författare)
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Interference modulation in the vibrationally resolved photoionization of the 1 sigma(g) and 1 sigma(u) core levels of the N-2 molecule
- 2006
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 39:12, s. L261-L267
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Tidskriftsartikel (refereegranskat)abstract
- The ratios of photoionization cross sections of the 1 sigma(g) and 1 sigma(u) shells of the N-2 molecule for the vibrational transitions to the nu' = 0 and nu' = 1 core-ionized states in the photon energy region between 440 and 550 eV have been measured. The calculations in the random phase approximation well reproduce the experimental data. The variation of the ratio with photon energy is attributed to the interference modulation that is caused by coherent photoemission from the two atoms, as an analogue of the Young's double-slit experiment. The calculations extended up to 1.8 keV allow connecting the modulation with the onset of transitions to the states of increasing orbital angular momentum which occurs at increasing photon energies and demonstrate that the main contribution to these modulations comes from the alpha continuum states.
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| 3. |
- Ueda, K., et al.
(författare)
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Role of the recoil effect on two-center interference in x-ray photoionization
- 2006
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Ingår i: Chemical Physics. - : Elsevier BV. - 0301-0104 .- 1873-4421. ; 329:1-3, s. 329-337
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Tidskriftsartikel (refereegranskat)abstract
- X-ray photoelectron spectra of the N-2 molecule are studied both experimentally and theoretically in the extended energy region up to 1 keV. The ratio of the photoionization cross sections for the gerade and ungerade core levels displays a modulation in the high energy region caused by the two-center interference, as predicted by Cohen and Fano (CF) in 1966. The physical background of this CF effect is the same as in Young's double-slit experiment. We have found that the interference pattern deviates significantly from the CF prediction. The origin of such a breakdown of the CF formula is the scattering of the photoelectron inside the molecule and the momentum transfer from the emitted fast photoelectron to the nuclei. Usually the recoil effect is small. We show that the electron recoil strongly affects the two-center interference pattern. Both stationary and dynamical aspects of the recoil effect shed light on the role of the momentum exchange in the two-center interference.
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