IR Spectra: Why is CO2 a doublet at 2350cm-1?

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The discussion centers on the existence of a "doublet" peak for CO2 at 2350 cm-1 in infrared spectroscopy, which raises questions about its origin. While DrDu notes that N-O bonds exhibit two peaks due to IR-active symmetric and asymmetric stretches, CO2's linear structure complicates this explanation. Chemistree suggests that the doublet arises from similar stretching modes, but this contradicts the expected behavior of a linear molecule. The concept of "Fermi resonance" is introduced as a potential explanation for the observed doublet in CO2. Understanding this phenomenon is crucial for interpreting IR spectra accurately.
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CO2 is supposed to create a "doublet" peak at 2350 cm-1 according to my IR correlation chart. Why is this doublet created? As DrDu explained in my previous post, two peaks are seen for the N-O bond because it has IR-active symmetric and asymmetric stretches. But CO2 is a linear molecule, and thus should not have an IR-active symmetric stretch.

I found another post on this forum in which chemistree explains the doublet as resulting from "symmetric and asymmetric" stretching, but that doesn't make sense to me considering the above. Does anyone know why the CO2 doublet exists? Thank you!
 
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