Hi Thao,

Below is a picture of gas phase mixture of NO2 and NO. You can clearly see the IR bands around 2200 cm-1 for N2O. Here is the reference DOI 10.1021/ac60090a040

As for the rotovibrational bands because you are in the gas phase the molecules are not just able to vibrate but are also able to rotate. Hence the Roto-Vibrational

Here is a link to help

https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Spectroscopy/Rotational_Spectroscopy/Rovibrational_Spectroscopy

Best,

Aaron

Aaron, thanks a lot for your answer. I read the post in the link you attached but it was quite hard to figure out how a rotovibration peaks(or bands) would look like in Ir spectrum just through words. Would you mind giving me a picture of an IR rotovibration peaks (or bands )?  Sincerely thanks

Dear Thao, please find attached the spectra of N2O. Pressure, resolution and Temperature are on the figures, path length was 195 mm, 16 scans; you will see many overtones and combinational bands and the PQR- and PR-band structure of the rotovibrational bands; The Q-band belongs to the pure vibrational transition, but due to quantum rules they are sometimes forbidden. I will also attached a high resolution NO spectra (PQR-rotovibrational-typ) with clear separation of the bands (due to the lower mass of NO) and a spectra of N2O5 with not good resolved rotational bands due to the higher mass of N2O5. KR Rodion