The infrared spectrum of the F−–H2 anion complex

The infrared spectrum of F−–H2 is measured over the H–H stretch region. The νHH transition occurs at 3220 cm−1, displaced 940 cm−1 to lower energy from the H2 fundamental vibrational transition. A weaker band at 3640 cm−1 is assigned to νHH in combination with the intermolecular stretch vibration (νHH + νs). The experimental νHH frequency agrees with a prediction based on an ab initio H–H potential energy curve calculated at the CCSD(T)/aug-cc-pVQZ level. Absence of resolved rotational structure in the νHH band suggests that rovibrational lines are lifetime broadened and that F−–H2 in the νHH = 1 level predissociates on a < 3 ps timescale.