Can the electron magnetic resonance (EMR) techniques measure the crystal (ligand) field parameters?

In this paper, the question posed in the title is critically examined on the basis of the available literature evidence implying the positive answer. The distinction between, on the one hand, the actual crystal field (CF) or equivalently li.-and field (LF) related quantities and, on the other hand, the actual zero-field splitting (ZFS) or equivalently fine structure (FS) quantities, is elucidated. The origin and possible roots of the incorrect terminology consisting in mixing up the two physically distinct quantities at different levels are examined. Aspects concerning Hamiltonians, parameters, energy level splitting, and nature of the operators involved are taken into account. Problems with the various notations for the operators and parameters used in the electron magnetic resonance (EMR) area are also identified and reviewed. A large number of cases of incorrect terminology and other inconsistencies identified in the course of a comprehensive literature survey are analyzed and systematically classified. Implications of the confusion in question, which go beyond the simple semantic issues, are discussed. The results of the survey reveal that the two most serious categories of this confusion lead to misinterpretation of the experimental EMR data. Several examples of serious misinterpretations found in the books, reviews, and original papers are discussed. The incorrect terminology contributes also to misleading keyword classifications of papers in journals as well as references in scientific literature databases. Thus, the database searches may produce unreliable outcomes. Examples of such outcomes are also shown. It is concluded that, in order to prevent further proliferation of the incorrect terminology and thus to increase reliability of the published EMR data, a concerted effort within the EMR community is indispensable. Various ways in this regard at the international level are suggested. (C) 2001 Elsevier Science B.V. All rights reserved.