H-atoms in H2​O are rearranged by strong optical fields generated by
intense, 10 fs laser pulses to form H2+​, against prevailing wisdom that
strong fields inevitably lead to multiple molecular ionization and the
subsequent Coulomb explosion into fragments. This atomic rearrangement is shown
to occur within a single 10 fs pulse. Comparison with results obtained with
∼300-attosecond long strong fields generated using fast Si8+ ions
helps establish thresholds for field strength and time required for such
rearrangements. Quantum-chemical calculations reveal that H2+​ originates in
the 1A state of H2​O2+ when the O-H bond elongates to 1.15 a.u. and
the H-O-H angle becomes 120o. Bond formation on the ultrafast timescale of
molecular vibrations (10 fs for H2+​) has hitherto not been reported.Comment: Submitted to Physical Review Lotter