Supersonic Dispersion and Absorption in CO2

Abstract

Since supersonic velocity determinations in air near a crystal oscillator usually yield values in excess of the accepted value, $V_0=331.6\mathrm{}$ m/sec., a similar effect with C${\mathrm{O}}_2$ was suspected. The velocity and the absorption coefficient were measured at frequencies beginning in the dispersion region, theoretically and experimentally investigated by Kneser, and extending beyond it to 2.09 megacycles. The author's velocity values are slightly less than Kneser's experimental values but they fit his theoretically determined dispersion curve equally well. At the lowest frequency tested (303 kilocycles) the absorption coefficient was found to exceed, by the greatest amount, its value computed from Lebedew's formula. This frequency is near the middle of the dispersion region where maximum absorption is expected. According to Pierce the absorption becomes excessive also when this frequency is approached from lower values. The results are presented in tabular and in graphical form. A sharp absorption maximum appears at 217 k.c.