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 experiment¹: coherent electron emission originates from two identical sites, and should give rise to characteristic interference patterns². 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 N₂ 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 experiments³.

1. Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin, Germany
2. Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany
3. California Institute of Technology, Pasadena, California 91125, USA
4. †Present addresses: Medical Faculty, Physics Department, University of Rijeka, 51000 Rijeka, Croatia (S.C.); Steacie Institute for Molecular Sciences, National Research Council Canada, Ottawa, Ontario K1A 0R6, Canada (O.G.); Institut für Physikalische Chemie, Universität Würzburg, 97074 Würzburg, Germany (B.L.); Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan (T.L. & G.P.); Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany (B.Z.)

Correspondence to: Uwe Becker¹ Correspondence and requests for materials should be addressed to U.B. (Email: becker_u@fhi-berlin.mpg.de).

Received 7 April 2005; Accepted 11 July 2005

MORE ARTICLES LIKE THIS

These links to content published by NPG are automatically generated.