OPTICAL, ZERO-FIELD ODMR AND EPR STUDIES OF THE TRIPLET-STATES FROM SINGLET FISSION IN BIPHENYL-TCNQ AND BIPHENYL-TETRAFLUORO-TCNQ CHARGE-TRANSFER CRYSTALS

被引:13
作者
AGOSTINI, G
CORVAJA, C
GIACOMETTI, G
PASIMENI, L
机构
[1] Department of Physical Chemistry, University of Padua, 35131 Padua
关键词
D O I
10.1016/0301-0104(93)80139-Z
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Biphenyl-TCNQ and biphenyl-tetrafluoro-TCNQ crystals, when excited with visible light, give rise to triplet excitons which were investigated by optical, EPR and zero-field (ZF) ODMR spectroscopies in a wide temperature range. The analysis of spin polarization carried by EPR and ZF ODMR spectra at room temperature enabled us to reveal the singlet depletion path S --> (T, T) which is thermally activated. The activation energies are DELTAE = 1940 cm-1 for B-TCNQ and DELTAE = 1720 cm-1 for B-TCNQF4. From the relation 2E(T) = E(S) + DELTAE the energies of the triplet state in the CT complexes were derived: E(T) = 9770 +/- 100 cm-1 for B-TCNQ and E(T) = 8695 +/- 100 cm-1 for B-TCNQF4. It was also established that the triplet species detected by ODMR at 1.8 K are populated by ISC.
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页码:177 / 186
页数:10
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