Ionization – dissociation of methane in ultrashort 400 nm and 800 nm laser fields

[Display omitted] •The dissociation mechanisms in CH4 for 800 nm and 400 nm laser fields.•A first step towards controlling the dissociation in CH4.•At lower intensities the extent of fragmentation is greater for 400 nm pulses.•Alternative dissociation pathways for higher laser intensities.•Quantum chemical calculations to identify the dissociation pathways. The effect of laser wavelength on the dissociation mechanisms in methane is examined over a broad range of intensities for both 800 nm and 400 nm laser fields. It is found that, at lower laser intensities, the dissociation pathways identified with the aid of theoretical calculations for the methane cation can account for most of the experimental findings, including the differences observed for irradiation by 800 nm and the 400 nm fields. As the laser intensity increases, the significance of the Coulomb explosion mechanism, along with the contribution of the rescattering process and the concomitant dissociation pathways, is highlighted.