Photodissociation of hydrogen iodide in the A-band region 273–288 nm

The photodissociation of hydrogen iodide in the A-band region was investigated between 273 and 288 nm using the photofragment imaging technique. At 17 wavelengths the I* (2P1/2)/I(2P3/2) branching ratio was measured by recording the corresponding hydrogen atomic fragment using multiphoton ionization at 243 nm. The branching ratios are in good agreement with previous measurements and confirm that four (final) states Π3(0+), 3Π(1), 3Σ(1), and Π1(1) are involved in the A-band absorption of HI and that those states dissociate adiabatically to form H+I* and H+I following parallel and perpendicular transitions, respectively. The deficiency of the model of three unbound states and that of the δ-approximation is substantiated.