A Stark Spectroscopic Study on a Flavin Langmuir–Blodgett Film

The molecular orientation of a flavin Langmuir–Blodgett film was investigated by Stark spectroscopy. The first-harmonic Stark spectrum was found to be close to the first derivative of the absorbance, indicating that the flavin (isoalloxazine) ring took a specific orientation toward the direction of the applied electric field instead of a random orientation. From the analysis of the Stark spectrum, it was deduced that difference dipole moments for the S 0 → S 1 and S 0 → S 2 transitions were almost parallel to the substrate in the direction of approximately 35° from the long axis of the isoalloxazine ring.