Molecular dynamics of methanol cation (CH3OH+) in strong fields: Comparison of 800 nm and 7 μm laser fields

Fragmentation and isomerization of methanol cation by short, intense laser pulses were studied by ab initio classical trajectory simulations using CAM-B3LYP/6-31G(d,p) calculations. Compared to random orientation, CH3OH+ with the CO bond aligned with the laser polarization gained nearly twice as much energy from the laser field, in accordance with the higher vibrational intensities in the mid-IR range for aligned CH3OH+. The energy gained by CH3OH+ from 7 μm and 800 nm laser pulses with intensities of 0.88 × 1014 and 1.7 × 1014 W/cm2 is proportional to the intensity and the wavelength squared of the laser field.