title: Orientational anisotropic studies by field rotation technique: near zero-field pulsed EPR experiments of pentacene doped in p-terphenyl.
abstract: 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.
authors.affiliation: Department of Chemistry, Washington University, St. Louis, MO 63130-4899, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Lang
authors.forename: David J
authors.initials: DJ
authors.lastname: Sloop
authors.forename: Tien-Sung
authors.initials: TS
authors.lastname: Lin
mesh_terms: 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*
chemical_list: D013730:Terphenyl Compounds