THERMAL RELAXATION IN NITROGEN WITH CH4 AND CD4 ADMIXTURES

Using the pressurized acoustic resonance tube developed in this laboratory, the shift in the napier (relaxation) frequency of nitrogen at 168°C has been measured as a function of percent of added methane, both normal and fully deuterated. The shift is linear up to 2% of impurity in each case, but is by far the greater with the deuterated methane: 1350 Hz/1% vs 240 Hz/1% for the ordinary. The degenerate unsymmetrical stretching mode of vibration at 2259 cmâ1 in deuterated methane differs by only 72 cmâ1 from nitrogen's vibration at 2331 cmâ1, and a resonance interchange of energy is clearly probable. The symmetrical stretch at 2109 cmâ1 is also within 10% of nitrogen. In the case of ordinary methane and nitrogen, there are no such near approaches. Precisely the reverse obtains in the case of oxygen and the two methanes. © 1969, Acoustical Society of America. All rights reserved.