Effect of Light Molecules on Vibrational Relaxation in Oxygen

Abstract

Sound absorption and velocity measurements have been made in O2 with added amounts of H2, D2, and He. The number of collisions Z10(AB) necessary to de-excite the first vibrational state of O2 has been calculated from the measured relaxation times. At 100°C: Z10(O2–H2)=2.0×104, Z10(O2—D2)=2.5×105. At 200°C: Z10(O2–H2)=1.1×104, Z10(O2—D2)=1.5×105, Z10(O2–He)=6.8×104. At 300°C: Z10(O2–He)=3.6×104. These values are in general agreement with values reported by Parker; by Holmes, Smith, and Tempest; and by White and Millikan. When logZ10(AB) is plotted vs the cube root of the reduced mass times the square of the vibrational frequency divided by the absolute temperature, a linear relationship is found between the O2–H2 and the O2–He data. However Z10(O2—D2) is unexpectedly larger than Z10(O2–He). When the collision numbers Z10, for pure O2 and N2, are plotted in this way they fall along a single curve.