Polarization of Transitions to the Magnetic Substates of Triplet Excitons

A development of the intensity relations for electronic transitions to the spin states of a molecular crystal which shows factor group splitting in its triplet levels is discussed. The relationships show that the unique polarization found in the case of the singlet Davydov states of a crystal with two molecules in the unit cell is recovered in the individual spin states of the triplet factor group levels. Experimental results consistent with our development are presented for the particular case of phenazine crystals. The singlet‐triplet transition of phenazine, origin at 15 448 cm⁻¹, is studied on the $a′b$ crystal face in a 50 kG magnetic field directed along the b axis with light polarized parallel and perpendicular to the direction of the magnetic field.