  Fano resonance in molecular spectroscopy is reported with a dual-comb
instrument. The effect is observed as asymmetric absorption lines of H12CN.
Pulse chirping conditions in the gas cell are varied to show that Fano
resonance is dependent on the pulse peak power. A model adding the Fano profile
to Voigt lines is used to estimate Fano phase as a function of pulse peak
power. A pulse peak power condition is derived from this analysis to avoid
lineshape distortion in pulsed laser experiments.
