The angular dependence of the EPR spectrum of a tetragonal (in the paramagn
etic phase) Gd3+-O2- center with large initial splitting is used to determi
ne the rotation angles of the neighboring chlorine octahedron, which are re
lated to the components of rotation modes, in the vicinity of room temperat
ure. Aspects of the anomalous broadening of the EPR lines near structural t
ransformations are discussed. (C) 1999 American Institute of Physics. [S106
3-7834(99)01202-2].