Coulomb explosion imaging of molecular hydrogen anions

With the recent confirmation of the existence of H-2 and its isotopologues, foil-induced Coulomb Explosion Imaging (CEI) offers a unique and straightforward method to investigate the fundamental structure of the molecular anion characterized by a lifetime on the order of 10 microseconds, large internuclear separations, and large angular momentum quantum numbers. Using an energetic (500 keV/amu) beam and the sub-femtosecond stripping of the molecule in an 5 nm thick diamond-like carbon foil, the total kinetic energy release (KER) of the subsequent Coulomb explosion is determined by event-by-event imaging of the fragments about 2 m downstream. Accounting for effects induced by the foil and the initial, substantial rotational energy, we find the distribution of internuclear distances of the metastable ion. Results are presented for measurements of H-2 and D-2