Knowledge Bank

Attempts to employ a spectrophone cell to measure vibrational life times through a study of small phase shifts raise the question of whether any processes other than the finite transition time from excited vibrational states to the ground state contribute to the observed phase shift. A fairly detailed theory of the transformation of radiant to acoustic energy has been developed and some aspects subjected, to experimental test. In the present work, we have demonstrated with a aeries of $N2O$ and argon mixtures that the total signal in a vibrational band is proportional to the first power of the total pressure times the square root of the mole fraction of the absorbing gas over a fairly broad range. This result corresponds to the so-called """"square root"""" region of effective line widths known in ordinary absorption spectroscopy. It enables one to place upper limits upon extraneous phase shifts in the life time experiment and suggests alternative possibilities for indirect measurement of integrated band intensities and or individual line breadths.