Orientational anisotropic studies by field rotation technique: near zero-field pulsed EPR experiments of pentacene doped in p-terphenyl.
We report a new technique to map the orientational anisotropy of paramagnetic systems without physically changing the crystal orientations in near zero-field (NZF) pulsed EPR experiments. By implementing three sets of orthogonal coils around the sample, we are ble to create a magnetic vector up to 2 mT in any three-dimensional orientation in space. In NZF region, the hyperfine tensor elements are comparable to the electronic Zeeman interaction energy, thus very rich spectral patterns can be obtained by "dialing" in a magnetic field vector without moving the sample. The technique further allows us to examine the site symmetry of organic crystals and powdered solids doped with chromophores which can be photo-excited to the triplet state by laser light. The technique is exemplified in the study of pentacene in p-terphenyl crystals.
Lang
Jun
J
Department of Chemistry, Washington University, St. Louis, MO 63130-4899, USA.
Sloop
David J
DJ
Lin
Tien-Sung
TS
D000465:Algorithms; D016880:Anisotropy; D003460:Crystallization / Q000379:methods*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D008280:Magnetics; D008968:Molecular Conformation; D012399:Rotation; D012666:Semiconductors; D012815:Signal Processing, Computer-Assisted; D013730:Terphenyl Compounds / Q000032:analysis* / Q000737:chemistry*
D013730:Terphenyl Compounds