Abstract: An acousto-microwave system to determine a mass M of gas disposed in a vessel includes: a microwave transmitter disposed on the vessel to transmit microwave radiation inside the vessel, a portion of the microwave radiation occurring at a microwave resonance of the vessel; a microwave receiver disposed on the vessel to receive microwave radiation communicated through an interior of the vessel from the microwave transmitter; an acoustic transmitter disposed on the vessel to transmit acoustic radiation inside the vessel, a portion of the acoustic radiation occurring at an acoustic resonance of the gas in the vessel; and an acoustic receiver disposed on the vessel to receive acoustic radiation communicated through the gas from the acoustic transmitter. The mass M of the gas is determined by analyzing the microwave radiation received by the microwave receiver and the acoustic radiation received by the acoustic receiver.

Abstract: A photoacoustic spectrometer that is intensity-modulated, laser-driven and with a calculable cell constant. The axially symmetrical photoacoustic spectrometer combines first-principles models of acoustic wave propagation with high-resolution spectroscopic measurements, and takes into account molecular relaxation. The spectrometer includes a duct and two chambers disposed at the end of the duct. Inlet and exit tubes, which are disposed in substantially the location of acoustic pressure nodes, permit the gas, gaseous mixture or aerosol to enter and exit the spectrometer. The absolute response of the spectrometer may be modeled and measured. A detailed theoretical analysis of the system and its predicted response may be predicted as a function of gas properties, resonance frequency and sample energy transfer relaxation rates.