Electric field splitting of the octatetraene 1 1A g→2 1A g transition in n-hexane

Octatetraene can be photoisomerized even when it is incorporated in a low temperature n-hexane crystal. When this is done by irradiating the zero-phonon component of the S0→S1 origin band with a single frequency laser, very narrow (∼10 MHz) persistent holes can be burned. We have determined the effect of an externally applied electric field on these persistent holes and fit the observed data with a simple quantum mechanical model parameterized in the S0→S2 and S1→S2 transition dipoles and the magnitude of a molecular field intrinsic to the n-hexane site occupied by the octatetraene guest. The magnitude of the molecular field (∼106 V/cm) is consistent with only one of the three possible n-hexane sites that could have accommodated the octatetraene guest.