SPIN-ECHO IN THE PHOSPHORESCENT TRIPLET-STATE OF CRYSTALLINE 2-INDANONE

The relative ordering of the three sublevels of the phosphorescent tri plet state of 2-indanone was determined by correlating optically detec ted magnetic resonance (ODMR) spectra taken with the sample in a Zeema n field with calculated spectra. Spin coherence was observed in the ph osphorescent triplet state of 2-indanone in neat and doped single crys tals by conventional and real time detection. The Hahn electron spin-e cho signal was observed in real time by a pulse sequence which termina tes with a continuous-wave low power field (LPF). The Fourier transfor m of the echo decay as a function of tau yielded a peak at 9.0 MHz whi ch was attributed by isotopic substitution studies to nuclear coupling of the triplet electrons via the alpha-protons in the molecule. Depha sing of the Hahn and stimulated spin echo in 2-indanone due to energy trapping was measured with chemically mixed crystals of 2-indanone pre pared with varying concentrations of quinoxaline. Energy transfer to q uinoxaline which served as a deep trap contributed to the dephasing of the echo.