Investigation of gaseous acoustic damping rates by transient grating spectroscopy

An investigation of acoustic damping rates in a pressurized gaseous medium by analyzing the temporal behavior of laser-induced gratings is reported. Experiments were performed in various nonresonant gas samples as a function of pressure and grating spacing. Acoustic damping rates were determined through model fits to the acquired signals. The results were compared with theoretical calculations using both classical acoustic damping rates and a more comprehensive model that includes rotational and vibrational energy transfer mechanisms. The relationships between the measured acoustic damping rate and molecular structure and pressure and grating spacing are discussed. The utility of exploiting the temporal signature from laser-induced gratings to determine acoustic damping rates in high-pressure gases is identified.