Lineshifts in the fundamental band of CO: Confirmation of experimental results for N-2 and comparison with theory

We have used a three-channel version of a tunable difference frequency lase r spectrometer to measure the collisionally induced lineshifts at room temp erature for 26 lines of the fundamental band of CO perturbed by nitrogen. E ach lineshift was obtained directly by comparing the Line center positions of two simultaneous recordings, one for a pressure-shifted line, and the ot her for the same line in pure CO line at very low pressure. The experimenta l results are found to be in complete agreement with earlier measurements a nd confirm. that shifts as small as 3 MHz may be measured in such a system. Our results are compared with theoretical calculations. The part of the sh ifting coefficient antisymmetric with respect to change in sign of the line number m, is in disagreement with the calculations. (C) 1999 Academic Pres s.