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

The ultrafast structural deformation of NO2 in an intense laser field (1.0 PW/cm(2)) is studied by mass-resolved momentum imaging (MRMI) of the Op+ an d Nq+ (p,q=1-3) fragment ions produced from NO2z+ through the Coulomb explo sion processes, NO2z+--> Op++Nq++Or+ (z=p+q+r). The N-O distance just befor e the Coulomb explosion is elongated significantly from that in the electro nic ground state, and it monotonically increases from 1.7 to 2.1 Angstrom a s z increases from 4 to 9. The angle O-N-O bond angle increases toward a li near configuration as a function of z, which is interpreted in terms of the formation of the light-dressed potential energy surfaces. The two-body fra gmentation pathways to produce NO+ and NO2+ are also investigated by the MR MI measurements to derive the extent of the asymmetrical bond elongation of one of the two N-O bonds. (C) 1999 American Institute of Physics. [S0021-9 606(99)00443-2].