Molecular hydrogen ion elimination from alkyl iodides under strong laser beam irradiation

The elimination of H2+ from alkyl iodides under strong (up to 5 × 1015 W cm−2) laser irradiation is studied by means of time-of-flight mass spectrometry. The study has been performed by using 60 fs (λ = 800 nm) and 35 ps (λ = 1064, 532, 355 and 266 nm) laser pulses. It is concluded that the H2+ ions are ejected from ionic states via Coulomb explosion processes. The molecular rearrangement leading to H2+ formation is attributed to a tunneling process through a H transfer barrier. For the case of methyl iodide, about 10% of the doubly charged parent ions undergo molecular rearrangement. From a comparison of the H2+/H+ ion yield ratio of the studied molecules, it turns out that the H2+ formation from H atoms bonded to a terminal carbon atom is more efficient than that arising from H atoms bonded to central C atoms of the molecular chain.