Positronium in MOFs: the Atom out of the box

P. Crivelli; D. Cooke; B. Barbiellini; B. L. Brown; J. I. Feldblyum; P. Guo; D. W. Gidley; L. Gerchow; A. J. Matzger

doi:10.1103/physrevb.89.241103

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arXiv · 1309.6497

Positronium in MOFs: the Atom out of the box

P. Crivelli·D. Cooke·B. Barbiellini·B. L. Brown·J. I. Feldblyum·P. Guo·D. W. Gidley·L. Gerchow·A. J. Matzger

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Abstract

Recently, evidence for positronium (Ps) in a Bloch state in self-assembled metal--organic frameworks (MOFs) has been reported [Dutta et al., Phys. Rev. Lett. 110, 197403 (2013)]. In this paper, we study Ps emission into vacuum from four different MOFs crystals: MOF-5, IRMOF-8, FMA and IRMOF-20. Our measurements of Ps yield and emission energy into vacuum provide definitive evidence of Ps delocalization. We determine with a different technique Ps diffusion lengths in agreement with the recently published results. Furthermore, we measure that a fraction of the Ps is emitted into vacuum with a distinctly smaller energy than what one would expect for Ps localized in the MOFs' cells. We show that a calculation assuming Ps delocalized in a Kronig--Penney potential reproduces the measured Ps emission energy.

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P. Crivelli, D. Cooke, B. Barbiellini, B. L. Brown, J. I. Feldblyum, P. Guo, D. W. Gidley, L. Gerchow, A. J. Matzger. 2013-09-25. Positronium in MOFs: the Atom out of the box. https://doi.org/10.1103/physrevb.89.241103

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