Accurate PAS measurements rely on accurate calibration of their signal. Ozone is often used for calibrating PAS instruments by relating the photoacoustic signal to the absorption coefficient measured by an independent method. We offer an alternative approach to calibrate photoacoustic aerosol spectrometers with aerosolized, light-absorbing organic materials. To implement this method, we first determined the complex refractive index of an organic dye, using spectroscopic ellipsometry.