Measured Transition Probability for the First-Positive Band System of Nitrogen

Abstract

The electronic transition probability for the nitrogen first-positive system has been obtained from absolute spectral-intensity measurements of the infrared radiation from shock-heated nitrogen. A 12-channel spectrometer was used, whose resolution was sufficient to separate the vibrational band sequences. The temperature dependence of the spectrum was shown to agree with that determined for nitrogen in thermodynamic equilibrium. An electronic transition moment | Re |2 equal to 0.096 a.u. and independent of internuclear separation gave the best fit to the data. The measured intensities are shown to be lower by a factor of 5 than those reported for measurements in shock-heated air, and the corresponding f number, evaluated at 9512 cm—1 (v′=v″=0), was found to be (2.8±0.7)×10—3. A second component of radiation was detected, and shown to be attributable to either the CN red or N2+ Meinel band systems.