PHENANTHRENE PROBE BEHAVIOR IN INCOMMENSURATE PHASE-II AND PHASE-III OF BIPHENYL

An investigation of the incommensurate phases II and III of biphenyl b y X-band Electron Paramagnetic Resonance (EPR) spectroscopy in a photo -excited state of hydrogenated and deuterated phenanthrene probe is pr esented. Some results in the high temperature phase are recalled. The spin Hamiltonian parameters in the incommensurate phases are given and their analysis shows that the phenanthrene molecules turn round a per pendicular direction to the long axis while the biphenyl molecules twi st around it. The EPR spectra of the phenanthrene allow us to give an easier conclusion about the Iq bi-domain structure of the biphenyl pha se II than the naphthalene ones. However, other complexities arise. Th e comparison of the results obtained with the phenanthrene and naphtha lene probes show that these two molecules are complementary.