Strong-field Rydberg-state Excitation of Nitrogen Dioxide Pre-Excited in the A2B2 State

We experimentally investigate the Rydberg-state excitation (RSE) process induced by a strong near-infrared (NIR) laser field for nitrogen dioxide (NO2) molecules which are initially excited in the A2B2 state by a UV laser field. Both the neutral parent NO2 and the fragments are observed to survive the strong laser field in high Rydberg states. It is found that the RSE yield of NO2 (A2B2) molecules depends on the intensity of the strong NIR laser, as well as the relative polarization and delay time between the NIR and the UV laser fields. Distinct different behaviors between RSE and strong-field ionization of NO2 (A2B2) are observed. Analysis indicates that the probability of recapturing the tunneling electron to form high Rydberg states is affected by the molecular orbitals of the excited state, and the RSE process can qualitatively reflect the changes of molecular structure during ultrafast dynamics of the excited state of molecules.