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Click to increase image sizeClick to decrease image size ACKNOWLEDGMENTS The excellent technical assistance of Angelika Brauer in preparing this manuscript is gratefully acknowledged. The assistance of Maren Stämmler and Angelika Brauer in sample preparations, measurements, and evaluations is much appreciated. The technical drawings of Figs. 5A and 5B have been provided by Bruker Optics GmbH, Ettlingen, Germany. The original spectra of Figs. 6 and 19 have been kindly provided by H. Fabian and S. Keller, respectively. Their discussions in producing these figures are acknowledged. Figures 18, 20, and 21 have been adapted from the literature with direct help of the authors (C.P. Schultz, P. Lasch). Their help is gratefully acknowledged.
Dieter Naumann (Sat,) studied this question.