ENDOR Spectra of Pyrene Excited Triplet State in Naphthalene-TCNB Crystals

Abstract

Triplet state traps, observed on optically excited single crystals of Naphthalene-TCNB doped with Pyrene, have been studied by EPR and ENDOR spectroscopy. The magnetic resonance lines recorded at low temperature (20 K) are shown to be due to triplet excitations localized almost completely on a Pyrene molecule. The complete hyperfine tensors of all the protons have been determined. The spin distribution is shown to be distorted in such a way that the triplet Pyrene molecule lacks the in-plane symmetry axes of the ground state molecule. The orientation of the triplet molecule in the crystal lattice and the relative orientation of Pyrene and TCNB are also discussed.

Electron spin relaxation times and internal motions of radicals in the solid state investigated by ENDOR and pulsed EPR

“…It should be noted that the comparison of a number of experimentally determined dipolar tensors with those calculated by using the M-S method shows that there is generally a much better agreement when the spin density distribution is all positive with respect to the case in which negative spin densities due to n-electron spin polarization are present [15].…”