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Shallow level muonium centre in CdS

Authors: J. M. Gil, H. V. Alberto, R. C. Vil√£o, J. Piroto Duarte, P. J. Mendes, N. Ayres de Campos, A. Weidinger, J. Krauser, Ch. Niedermayer, S. F. J. Cox

Ref.: Physica B: Condens. Matter 289/290, 563-566 (2000)

Abstract: A new type of muonium defect centre has been observed in undoped CdS at low temperatures (T < 20K), The hyperfine parameters are A(parallel to) = 335 (7)kHz and A(perpendicular to) = 199 (6) kHz (approximately 10(-4) of the vacuum value) with the symmetry axis along the Cd-S bond direction. The disappearance of the centre at around 20 K is in agreement with the binding energy of a shallow centre. The extremely weak hyper fine interaction implies that the electron is only weakly bound to the muon acid is distributed over a large complex of atoms in the neighborhood of the muon resembling the dilated hydrogen-like wave functions of shallow centres in a dielectric medium. Comparing the hyperfine interaction with that of free muonium, a Bohr radius of a(d) = 26a(0) = 1.4 nm is calculated for this defect, with a(0) being the Bohr radius for the free muonium, (C) 2000 Elsevier Science B.V. All rights reserved.

DOI: 10.1016/S0921-4526(00)00257-X