Mr. Diddeniya,

Without callibration you data cannot be assigned even as qualitative ones.

Thank you very much John Clarkson. That information was really helpful.

Actually, I've obtained Raman spectra not from a commercial Raman spectrometer, but from a Raman microscope setup I've made with suitable optics using (ocean optics QE65 Pro) as the detector. Obtained spectra are very much agreeable with standard values but have that shift I've mentioned earlier.

However, the spectrometer was not calibrated for wavelengths.

Could you please let me know at this situation, what should I do?

Is there any method that can fix the error?

I've attached a spectrum I've got for Naphthalene and its' reference spectrum