Abstract: The SERRS spectra of sodium fluorescein at various pH values adsorbed on silverisland film are presented. Due to the fact that sodium fluorescein exists in different ionic forms in the solutions at different pH values, these SERRS spectra are different. The difference lies not in the freciuency, but in the intensity of Raman bands. The intensity variation of the band with the pH value falls into two categeries depending on the nature of corresponding modes of vibration. The experimental results are interpred by using a "four-level model" with the theory of resonance Raman scttering.

Key words: Sodium fluorescein, SERRS