Collision halfwidth temperature dependence

Among other new methods, tunable laser absorption spectroscopy using infrared diode lasers offers prospects for improved accuracy and specificity in concentration measurements, when a line-of-sight technique is appropriate. The present paper discusses diode laser techniques as applied to a flat flame burner and to a room temperature absorption cell. The cell experiments are used to determine the absorption band strength which is needed to properly interpret high temperature experiments. Preliminary results are reported for CO concentration measurements in a flame, the fundamental band strength of CO at STP, collision halfwidths of CO under flame conditions, and the temperature dependence of CO and NO collision halfwidths in combustion gases. 

The temperature dependence of the collision halfwidth, 2y(T), is of fundamental and practical interest and has not previously been investigated at elevated temperatures. In the past, most determinations of collision halfwidth have been made near room temperature, and high-temperature values have been obtained by extrapolation, usually assuming a T 0>5 temperature dependence so that... 

Results showing the dependence of the CO collision halfwidth in combustion gases on the vibrational and rotational quantum numbers are shown in Figure 6. The data were obtained with a flame temperature of 1875 K and equivalence ratios in the range 1.2 - 1.4. Although too few data points are available for a detailed analysis, it is clear that 2y decreases with increasing m and that values for 2y are nearly equal (within 5%) for ground state and excited state transitions. 

The temperature dependence of the collision halfwidth for combustion gas broadening is also of interest. Results for specific transitions in CO and NO are given in Table I. In the... 

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