Crystal Field Induced Dipole Moments: The Stark Spectrum of Naphthacene in Benzophenone

In the polar host crystal benzophenone, the nonpolar guest naphthacene exhibits different dipole moments in its ground and first excited state. The dipole moment changes upon excitation for three guest sites are 1.2, 0.35, and 0.61D, as measured by low-temperature Stark techniques. The dipole moments are attributed to the polarizability of the guest in the electrostatic crystal field of the host, which is estimated to be ∼ 107 V/cm.