The Real-Time Advantage

Raman Spectroscopy is a very powerful technique used in the determination of a material's chemical/physical make up. Minimal requirements for sample preparation combined with short analysis times have made Raman a smart choice for a host of analytical/identification measurements.

There are two common phenomena that can interfere with successful Raman identification or characterization:

1. Fluorescence
2. Inaccurate Wavenumber Assignment

At RTA we design our Raman instruments to eliminate both.

What each of these phenomena mean and how they affect Raman analysis.

Fluorescence - is a signal generated by a part of a material that undergoes an electronic transition to an excited state. This causes the emission of light at a different wavelength from the excitation source. What this means is... you get interference that can completely obscure the Raman signal. See figure below. We do not use "Fluorescence Correction" or any mathematical means to try to determine what signal is Raman and what is fluorescence. We AVOID Fluorescence by exciting the sample with laser light enough to give a strong Raman signal, but not enough to induce fluorescence. This is the only proper way to generate reliable spectra that can be used for accurate material characterization.

Spectra of Wheat Flour using 785 nm and 1064 nm Raman excitation. Fluorescence interference generated when using 785 nm laser completely obscures critical Raman spectral features.

Innacurate Wavenumber Assignment - this phenomenon occurs as a function of a number of environmental factors. Ultimately what results is that peaks are assigned incorrect frequencies or Raman shifts which can dramatically reduce the ability to identify a material via spectral library matching. RTA uses an interferometer with a reference laser and is constantly verifying correct x-axis assignment. This means an incredibly stable instrument with reliable and reproducible wavelength assignments. What this also means is that there is no need to calibrate the instruments before use, this is not true for Dispersive Raman Instruments which require frequent calibration and suffer from "x-axis" drift.

Fourier-Transform (FT) Raman Advantages: 

• No sample preparation required
• Fluorescence interference avoidance
• Complete Spectral coverage

Wavelength (x-axis) stability provides:

• Accurate library search/match
• Accurate spectral subtraction
• Accurate chemometric model development