Effects of time-odd electron-phonon coupling in ligand field theory

The magnetic effects associated with ligand motion (e.g. a ligand-current-induced Zeeman coupling) might be distinguishable in the context of the spectroscopy of condensed matter through their time-odd character. In many ligand-field-related situations the time reversal signature of all interactions, taken jointly, is of importance in inducing selection rules. Time-odd coupling would give rise to novel combinations of temperature, field and excited state energy in spin-lattice relaxation times; in Raman phonon spectroscopy it would generate distinctive chiral phenomena; as noted by Fletcher (1981) it would give breakdown of Jahn-Teller reduction factor sum rules; it would also give rise to complex values of the Berry phase factor in Jahn-Teller systems. Similar characteristic evidences for time-odd coupling effects may be expected for lanthanide 4f to 4f transition intensities and in virtual phonon exchange.