Strong-field ionization of diatomic molecules and companion atoms: Strong-field approximation and tunneling theory including nuclear motion

We present a detailed comparison of strong-field ionization of diatomic molecules and their companion atoms with nearly equal ionization potentials. We perform calculations in the length and velocity gauge formulations of the molecular strong-field approximation and with the molecular tunneling theory, and in both cases we consider effects of nuclear motion. A comparison of our results with experimental data shows that the length gauge strong-field approximation gives the most reliable predictions.

Figure 1

Intensity-dependent ratios between the yields of ${\mathrm{N}}_2$ and Ar ions. In both panels the laser wavelength is $800\mathrm{nm}$. In panel (a), the pulse duration is $30\mathrm{fs}$ and the experimental data is from Ref. 11. In panel (b), the pulse duration is $100\mathrm{fs}$ and the experimental data is from Ref. 12. The thin lines are calculations with fixed nuclei and the thick lines are the corresponding calculations including vibrations.

Figure 2

The ionization rates of ${\mathrm{N}}_2$ and Ar (dotted) at intensities around the first channel closings obtained from (a) MO-SFA LG and (b) MO-SFA VG. For ${\mathrm{N}}_2$, we give the rates at parallel (solid) and at perpendicular geometry (long-dashed). The wavelength is $800\mathrm{nm}$ and the intensities at which the channels close for ${\mathrm{N}}_2$ are indicated by the arrows. Ar has a slightly higher ionization potential and the corresponding intensities lie at bit lower.

Figure 3

Intensity-dependent ratios between the yields of ${\mathrm{D}}_2$ and Ar ions. In both panels the laser wavelength is $800\mathrm{nm}$. The thin lines are calculations with fixed nuclei and the thick lines are the corresponding calculations including vibrations. In panel (a), the pulse duration is $100\mathrm{fs}$ and the experimental data is from Ref. 13. In panel (b), the pulse duration is $200\mathrm{fs}$ and the experimental data is from Ref. 10.

Figure 4

Intensity-dependent ratios between the yields of ${\mathrm{O}}_2$ and Xe ions. In all panels the laser wavelength is $800\mathrm{nm}$. The thin lines are calculations with fixed nuclei and the thick lines are the corresponding calculations including vibrations. In panel (a), the pulse duration is $30\mathrm{fs}$ and the experimental data is from Ref. 11. In panel (b), the pulse duration is $100\mathrm{fs}$ and the experimental data is from Ref. 12. In panel (c) the pulse duration is $220\mathrm{fs}$ and the experimental data is from Ref. 8.

Figure 5

Intensity-dependent ratios between the yields of CO and Kr ions. In panel (a) the laser wavelength is $800\mathrm{nm}$ and the pulse duration is $100\mathrm{fs}$. In panel (b) the laser wavelength is $1365\mathrm{nm}$ and the pulse duration is $80\mathrm{fs}$. In both panels the experimental data is from Ref. 13. The thin lines are calculations with fixed nuclei and the thick lines are the corresponding calculations including vibrations.

Figure 6

Intensity-dependent ratios between the ion yields of (a) ${\mathrm{S}}_2:\mathrm{Xe}$, (b) SO:Xe, and (c) NO:Xe. In all panels the laser wavelength is $800\mathrm{nm}$, the pulse duration is $100\mathrm{fs}$, and the experimental data is from Ref. 13. The thin lines are calculations with fixed nuclei and the thick lines are the corresponding calculations including vibrations.

Figure 7

Intensity-dependent ratios between the ion yields of (a) ${\mathrm{S}}_2:\mathrm{Xe}$, (b) SO:Xe, and (c) NO:Xe. In all panels the laser wavelength is $1365\mathrm{nm}$, the pulse duration is $80\mathrm{fs}$, and the experimental data is from Ref. 13. The thin lines are calculations with fixed nuclei and the thick lines are the corresponding calculations including vibrations.