OPTICALLY DETECTED MAGNETIC RESONANCE ON A BENZIL X-TRAP

Author Institution: Department of Chemistry, Brandeis University WalthamThe structure and photophysical properties of the major X-trap ($D=+0.012$ $cm^{-1}$,E=-$0.03 cm^{-1}$)$^{1}$ in nominally pure benzil single crystals have been investigated with optically detected high-field magnetic resonance. The orientations of the principle fine-structure axes have been determined relative to the crystal axes. The y-axis is coincident with one of the two-fold axes of the crystals. The z-axis makes an angle of $64\pm 2^\circ$ with the crystalline c-axis. (For the crystal structure of benzil see Brown and $Sadanaga.^{2}$) As suggested $earlier^{1}$ the dicarbonyl fragment of benzil probably assumes trans-(near) plannar geometry in the phosphorescent state. The implications of the orientations of the fine-structure axes within the context of this geometry will be discussed. The consequences of this conformation on the photophysical behavior of benzil will be presented