Dynamic imaging a relaxed chemical bond using Infrared laser pulses

According to the quantitative rescattering (QRS) theory, the high-energy ATI (HATI) electron spectra from a molecule M can be used to extract the backscattering differential cross section (DCS) for e$^{-}$+M$^{+}$ collisions. In this talk, we will present our analysis of experimental HATI data with MIR lasers for N$_{2}$ and O$_{2}$. The N-N bond length retrieved from the HATI spectra agrees with that for N$_{2}$ to within 5{\%}. For O$_{2 }$the retrieved bond length is consistently much smaller than the known O-O bond length, 1.21{\AA}. Instead, it is much closer to the bond length of O$_{2}^{+}$, 1.12{\AA}. We interpret this result in terms of bond relaxation of O$_{2}$ following tunneling ionization. O$_{2}^{+}$ has a vibrational period of 17 fs while the returning time for a 2000 nm laser is about $\sim $5-6 fs, thus allowing the two O atoms to relax from its initial separation of 1.21 {\AA} to the new separation of 1.12 {\AA} of O$_{2}^{+}$.