Effects Of Molecular Structure on Ion Disintegration Patterns In Ionization of ${\mathrm{O}}_{\mathrm{2}}$ and ${\mathrm{N}}_{\mathrm{2}}$ by Short Laser Pulses

We demonstrate that the structure of the outermost orbitals of oxygen and nitrogen can be observed in the angular distribution of coincident ion pairs generated by the double ionization of these molecules by 8 fs laser pulses. We do this by establishing that these ions emerge from well defined excited electronic states of ${\mathrm{O}}_{\mathrm{2}}^{\mathrm{2}\mathrm{+}}$ and ${\mathrm{N}}_{\mathrm{2}}^{\mathrm{2}\mathrm{+}}$ respectively and that they are produced dominantly through a process which involves electron rescattering. The angular distributions of the ions from the two targets are very different, reflecting the different structures of the outermost orbitals of the two molecules.

Figure 1

Schematic of double ionization processes.

Figure 2

Slices in the xz plane of the momentum sphere showing the dissociation of molecules into two singly charged ions ${\mathrm{O}}_{\mathrm{2}}$ (upper panel) and ${\mathrm{N}}_2$ (lower panel).

Figure 3

Kinetic energy release spectra for ${\mathrm{O}}_{\mathrm{2}}$ (upper panel) and ${\mathrm{N}}_2$ (lower panel).

Figure 4

Polar plots of the experimental angular distributions for different decay channels for ${\mathrm{O}}_{\mathrm{2}}$ (left) and ${\mathrm{N}}_2$ (right).

Figure 5

Polar plots of the theoretical angular distributions expected for the removal of the outermost electron from ${\mathrm{O}}_{\mathrm{2}}$ (upper panel) and ${\mathrm{N}}_{\mathrm{2}}$ (lower panel). The schematic at the right shows the orbital structures of these orbitals.