THE ZERO-FIELD ODMR AND ENDOR SPECTRA OF THE TRIPLET STATE OF OXYGEN-17 LABELLED BENZOPHENONE

Abstract

We report the observation and detailed analysis of optically-detected magnetic resonance (ODMR), radio frequency (RF) saturated ODMR and electron-nuclear double resonance (ENDOR) spectra of the lowest $^{3}(n\pi^{*})$ state of oxygen-17 labelled benzophenone ($^{17}O$-BP) in zero-field (zf). The experiments were performed at 1.4K on a single crystal sample of 4,4^{\prime}-dibromidiphenylether (DDE) containing 0.1 mol % of an isotopically-enriched guest ($^{17}O$-BP; 11.3%). Allowed transitions and forbidden transitions were assigned from low power ODMR spectra and RF saturated ODMR spectra respectively. These assignments were confirmed by ENDOR experiments. The hyperfine coupling constants and nuclear quadrupole coupling constants ($e^{2}$qQ and $\eta$) were obtained for the $^{17}O$ atom. The data indicate that (1) the n electron is highly localized on the oxygen atom in $^{3}(n\pi^{*})$ benzophenone, (2) the higher order hyperfine interaction is important due to large hyperfine coupling constants of $^{17}O$.