Relaxation Time in CO2 as a Function of H2 and D2 Concentration at Several Temperatures

The frequency of maximum ultrasonic absorption was determined for CO2 with varying small amounts of the impurities H2 and D2 at three different temperatures. Hydrogen was found to be 2.4 times more effective than D2 in quenching the vibration of CO2 at both 47° and 154°C. More unexpectedly, it was found that the rate of shift of the frequency of maximum absorption with impurity concentration is less at high temperature than at low, and this fact is shown to imply that A—B collisions are 15%—20% less effective at the higher temperature than at the lower. The relaxing specific heat determined experimentally was found to be 5%—8% greater than the spectroscopic value over the entire temperature range.