Strong fields induce ultrafast rearrangement of H-atoms in H${}_2$O

Abstract

H-atoms in H${}_2$O are rearranged by strong optical fields generated by intense, 10 fs laser pulses to form H${}_2^{+}$, 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 $\sim$300-attosecond long strong fields generated using fast Si${}^{8+}$ ions helps establish thresholds for field strength and time required for such rearrangements. Quantum-chemical calculations reveal that H${}_2^{+}$ originates in the ${}^1$A state of H${}_2$O${}^{2+}$ when the O-H bond elongates to 1.15 a.u. and the H-O-H angle becomes 120${}^o$. Bond formation on the ultrafast timescale of molecular vibrations (10 fs for H${}_2^{+}$) has hitherto not been reported.

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