Study on laser Raman spectrum with different excitation wavelength

The laser Raman spectroscopy can provide quick, simple, repeatable, quantitative non-destructive analysis and does not require sample preparation and is applied in chemistry, physics, biology, medicine and other fields. The short-wavelength laser (blue or ultraviolet) and the long-wavelength laser (red or infrared) can be used as the excitation source. In this work, we find that some Raman peak of the molecular characterization will weaken or even disappear when a longer or shorter wavelength laser used as the excitation source. We present the Raman spectra of benzene and that of cyclohexane as an example, which are excited by different wavelength laser. The experimental results show that the Raman peak corresponding to the vibration of CH(CH Raman mode) is much stronger than that of the C Ring(C Ring Raman mode) when the excitation wavelength is 488 nm. When the wavelength increase to 785 nm, the CH Raman mode almost disappears and the C Ring Raman mode increases sharply. This experimental phenomenon will be benefits to the problem-solving of the analysis formula of Raman peak intensity. At the same time, it should be paid attention in the Raman spectral analysis to the effect of excitation wavelength on it.