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Optical Nuclear Polarization in the 1:1 CT‐Crystal Anthracene/Tetracyanobenzene. Consequences of the Phase Transition at 206 K
Author(s) -
Auch W.,
von Schütz J. U.
Publication year - 1980
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221010130
Subject(s) - anthracene , chemistry , excitation , coupling constant , quadrupole , exciton , magnetization , crystal (programming language) , polarization (electrochemistry) , phase transition , triplet state , molecular physics , magnetic field , nuclear magnetic resonance , condensed matter physics , molecule , atomic physics , physics , photochemistry , particle physics , quantum mechanics , organic chemistry , computer science , programming language
In the 1:1 CT‐complex anthracene/tetracyanobenzene the optical excitation of triplet states causes a nuclear polarization (ONP), which is two orders of magnitude larger than the Boltzmann magnetization. In single crystals this ONP is investigated as a function of the temperature (1.6 K ≦ ≦ T ≦ 300 K), of the magnetic field (0 < B p ≦ I T) and of the angle between B p , and the molecular axes. From the extrema of the ONP curves the identity and orientation of the triplet state inducing the ONP may be determined. In addition from cross‐relaxation experiments a quadrupole coupling constant A = (1.0 ± 0.1) MHz and an asymmetry factor η = 0.08 ± 0.02 for the 14 N nuclei of TCNB is found. Below the phase transition temperature at T e = ± 206 K the anthracene molecules occupy two magnetically inequivalent positions. For the ONP process between 205 and 40 K this magnetic inequivalence is released by the delocalisation of the triplet state as an exciton.