Ultrafast structural deformation of NO2 in intense laser fields studied by mass-resolved momentum imaging

The ultrafast structural deformation of NO2 in an intense laser field (1.0 PW/cm2) is studied by mass-resolved momentum imaging (MRMI) of the Op+ and Nq+ (p,q=1–3) fragment ions produced from NO2z+ through the Coulomb explosion processes, NO2z+→Op++Nq++Or+ (z=p+q+r). The N–O distance just before the Coulomb explosion is elongated significantly from that in the electronic ground state, and it monotonically increases from 1.7 to 2.1 Å as z increases from 4 to 9. The ∠O–N–O bond angle increases toward a linear configuration as a function of z, which is interpreted in terms of the formation of the light-dressed potential energy surfaces. The two-body fragmentation pathways to produce NO+ and NO2+ are also investigated by the MRMI measurements to derive the extent of the asymmetrical bond elongation of one of the two N–O bonds.