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Published September 29, 2005 | public
Journal Article

Isotope-induced partial localization of core electrons in the homonuclear molecule N_2

Abstract

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.

Additional Information

© 2005 Nature Publishing Group. Received 7 April 2005; Accepted 11 July 2005. We thank J. Bozek, R. Diéz Muiño, F. J. García de Abajo, C. S. Fadley and M. A. Van Hove for many discussions about core–hole delocalization and coherent photoelectron emission in homonuclear molecules. The assistance of R. Püttner and F. Gelmukhanov in the interpretation of the effect of isotope substitution on the vibrational structure and the Franck–Condon factors is also acknowledged. The work was partly supported by the Bundesministerium für Bildung und Forschung (BMBF) and the Alexander von Humboldt Foundation (B.Z.).

Additional details

Created:
August 19, 2023
Modified:
October 20, 2023