Assignment of peaks in photodetachment spectra using predicted densities of reactive states: Application to H2F− and D2F−

Abstract

Accurate cumulative reaction probabilities and densities of reactive states have been obtained for the reactions F+H₂→H+HF and F+D₂→D+DF using the hyperspherical (APH) coordinate scattering method developed by Pack and Parker. Results for scattering energies ranging from threshold to 0.7 eV above threshold have been obtained using two different potential energy surfaces that have been proposed for this system. The predicted peaks in the densities of reactive states are due to the presence of scattering resonances. The characteristic steps in the cumulative reaction probabilities are used to identify the resonance peaks due to quantized dynamical bottlenecks. The trapped‐state or Feshbach‐type resonances are identified by narrow oscillations in the density of reactive states. The positions of these resonance peaks in the density of reactive states are in good agreement with the peaks in the Franck–Condon factors for the photodetachment of H₂F⁻ and D₂F⁻. Significant changes in resonance types are found for the T5a and 5SEC potential energy surfaces for H₂F. While the assignment of resonance peaks presented is in reasonable agreement with the assignments suggested by Hahn and Taylor based on their classical mechanical analysis, there are some differences that will require further study.