ABSTRACT Raman spectroscopy provides a powerful optical means for identifying and characterizing materials through their inelastic light scattering signatures. In our previous work, we introduced Super‐Spectral‐Resolution Raman Spectroscopy (SSR‐RS), which enhanced spectral resolution by angle‐tuning a Fabry–Pérot (F‐P) etalon that was integrated into a dispersive micro‐Raman spectroscopy setup. In the present study, we introduce Inter‐Theta‐Gram Spectroscopy by modifying the SSR‐RS configuration to enable the simultaneous measurement of both the Raman excitation laser line and the Raman‐scattered signal during each angular scan. This dual‐channel approach allows precise determination of the absolute Raman shift by compensating for laser wavelength drift and instability. We applied the Inter‐Theta‐Gram technique to one lab‐grown and two natural diamond samples. The diamond's single, sharp Raman band at ~1332 cm −1 served as an ideal test case for validating the method's precision and reproducibility and for demonstrating the ability of the method to resolve subtle spectral differences among the specific measured samples. By jointly reconstructing the angular response of the laser and Raman peaks, we achieve ultranarrow effective linewidths and highly accurate absolute Raman shift values. The reconstructed Raman shifts were measured to be 1331.31 cm −1 for the lab‐grown diamond and 1331.43 and 1331.49 cm −1 for the two natural diamonds. These results confirm that Inter‐Theta‐Gram Spectroscopy preserves the ultrahigh spectral resolution of the original SSR‐RS method while enabling resolution of subtle sample‐dependent differences between the measured diamond samples, on the order of approximately 0.15 cm −1 .
Amiel et al. (Thu,) studied this question.