Symmetry breaking by quantum coherence in single electron attachment

Krishnakumar, E.; Prabhudesa, Vaibhav S. and Mason, Nigel J. (2018). Symmetry breaking by quantum coherence in single electron attachment. Nature Physics, 14(2) pp. 149–153.

DOI: https://doi.org/10.1038/nphys4289

Abstract

Quantum coherence-induced effects in atomic and molecular systems are the basis of several proposals for laser-based control of chemical reactions. So far, these rely on coherent photon beams inducing coherent reaction pathways that may interfere with one another, in order to achieve the desired outcome. This concept has been successfully exploited for removing the inversion symmetry in the dissociation of homonuclear diatomic molecules, but it remains to be seen if such quantum coherent effects can also be generated by interaction of incoherent electrons with such molecules. Here we show that resonant electron attachment to H2 and the subsequent dissociation into H (n=2) + H⁻ is asymmetric about the inter-nuclear axis, while the asymmetry in D₂ is far less pronounced. We explain this observation as due to attachment of a single electron resulting in a coherent superposition of two resonances of opposite parity. In addition to exemplifying a new quantum coherent process, our observation of coherent quantum dynamics involves the active participation of all three electrons and two nuclei, which could provide new tools for studying electron correlations as a means to control chemical processes and demonstrates the role of coherent effects in electron induced chemistry.

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