Fig. 1. (a) Mean wavelength shift (MWS) of the probe pulse as a function of the time delay between the pump and probe pulses at N2 gas pressure of 1 bar. (b) Typical shifted spectra of the probe pulses at alignment delay of 80.47 ps (red dotted curve) and 80.27 ps (blue solid curve), respectively. The original spectrum of the probe pulse (black dashed curve) is also shown for comparison. The inset shows the detailed structure of MWS at the revival time.

Fig. 2. (a) Deduced normalized molecular alignment 〈〈cos2θ(t)〉〉 from the measured result of Fig. 1(a). (b) The normalized comparison of delay-dependent MWS and molecular alignment 〈〈cos2θ(t)〉〉 in the time window of 0–12 ps.

Fig. 3. Degree of molecular alignment expressed in logarithmic coordinates as a function of multiple revival periods (i.e., 4.8, 13.2, 21.53 ps…) in (a) nitrogen and (b) oxygen. The gas pressure was fixed at 300, 700, and 1000 mbar, respectively.

Fig. 4. Decoherence lifetimes measured with the incident pump laser energies of 0.24, 1.3, and 2.5 mJ in (a) nitrogen and (b) oxygen. The gas pressure in both cases was fixed at 1000 mbar.

Fig. 5. Relative rotational populations of molecular rotational wave packets in (a) nitrogen and (b) oxygen are obtained via performing Fourier transforms of the corresponding curves in Figs. 4(a) and 4(b).