The photophysics of rhodamine B

Abstract

The effects of solvent viscosity and dielectric constant on the photophysics of rhodamine B in its protonated and zwitterion forms were studied. The internal conversion rate is dependent on the S1-S0 energy separation and increases when this gap is lowered through rotation of the diethylamino groups. Comparison is made with rhodamine 640 in which torsional motion about the C-N bond is not possible. © 1982.