The dynamic interchange and relationship between germanium centers in α-quartz

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Abstract
The Ge3+ centers [GeO−4(I)]− ≡Ge(I), [GeO4−(II)]− ≡Ge(II), and B, which are produced by x irradiation of α‐quartz containing germanium, have been studied by EPR. The spin‐Hamiltonian parameters ḡ, Ā73Ge, Ā29Si(1)⋅⋅ ⋅Ā29Si(4) for Ge(I), and ḡ, Ā73Ge for Ge(II), both sets measured at ≈15 K, and ḡ, Ā73Ge for B at ≈220 K are reported. The direction of the sp hybridized germanium orbital of the unpaired electron is found to coincide with the bisector of one of the O–Si–O angles [106.3° from the crystal c axis for Ge(I); crystal twofold axis for Ge(II)]. Centers Ge(I) and Ge(II) are found to be different, energetically inequivalent versions of the same basic center. The B center appears as a result of rapid electron jumping between Ge(I) and Ge(II) above ≈150 K. The observed line positions of B coincide with ones calculated from motional averaging among three states: two of Ge(I) and one of Ge(II). The relative Ge(I) and Ge(II) concentrations are obtained from signal intensity ratios at low temperatures (14:1 at ≈15 K, 4.4:1 at ≈80 K) and from the line positions of center B at sufficiently high temperatures (3.0:1 at ≈220 K, 2.7:1 at ≈300 K).