Investigation of the role of photoacoustic phase in N2O(v) vibrational relaxation rate determination

This study investigates the relaxation dynamics of the ν3 energy level of nitrous oxide (N2O) molecules in synthetic air using a 4.5 μm distributed feedback quantum cascade laser (DFB-QCL) combined with photoacoustic spectroscopy (PAS) technique. A comprehensive theoretical model coupling vibration-translation (V-T) relaxation processes and vibration-vibration (V-V) energy transfer was developed, enabling a rigorous theoretical derivation of the system-wide vibrational relaxation time. Through in-depth analysis of photoacoustic signal phase characteristics, the molecular relaxation times of both N2O (ν3) (1.6 μs atm) and H2O (0.33 μs atm) were simultaneously extracted. Thorough cross-validation against literature values demonstrated that photoacoustic phase information serves as a highly sensitive probe for detecting gas molecular energy relaxation processes. This research not only validates the technical feasibility and analytical superiority of PAS phase technology in measuring gas relaxation times but also introduces a novel high-precision spectroscopic analysis method for studying vibrational dynamics in complex molecular systems, showcasing its potential applications in environmental monitoring and molecular dynamics research.