Photoelectron-photofragment angular correlations in the dissociative photodetachment of HOCO⁻

A coincidence study of the photoelectron-photofragment angular distributions in the one- and two-photon dissociative photodetachment (DPD) of HOCO⁻ is reported. The photoelectron angular distributions in the one-photon DPD channels HOCO⁻ + hν → OH + CO + e⁻ and HOCO⁻ + hν → H + CO₂ + e⁻ at E _hν = 3.21 eV are examined in both the laboratory and neutral photofragment recoil frames, while the angular distributions of the OH + CO products in the laboratory frame are also investigated. The results show a parallel dipole transition for the DPD of HOCO⁻. The radical lifetime was examined as a function of the orientation of the transition dipole, with upper limits of 9 × 10⁻¹³ s and 1.3 × 10⁻¹² s estimated for HOCO and DOCO lifetime for dissociation into OH/OD + CO, respectively. The photoelectron-photofragment angular correlation in the two-photon DPD of HOCO⁻ is also presented, showing that when the photon energy is near the photodetachment threshold, a molecular anion like HOCO⁻ can be effectively aligned through a continuum shape resonance.

Keywords

• dissociative photodetachment, recoil-frame photoelectron angular distribution