We develop the theory of dissociative electron attachment (DEA) to ${\mathrm{H}}_2$ and ${\mathrm{D}}_2$ molecules in the 14–18 eV region where attachment is driven by two resonances of ${}^2{\mathrm{\Sigma }}_g{}^{+}$ and ${}^2{\mathrm{\Sigma }}_u{}^{+}$ symmetries. Special attention is given to the description of angular asymmetry in this process due to the coherent superposition of the two resonances. The fixed-nuclei calculations of the resonance potential energy curves and their widths are carried out by the R-matrix method. Vibrational dynamics is then included within the framework of the local complex potential model. Our attempt to describe the angular asymmetry observed in the DEA process [E. Krishnakumar et al., Nat. Phys. 14, 149 (2018).] leads only to a qualitative description of this experiment because of insufficient accuracy of R-matrix calculations at large internuclear separation. This also leads to a large uncertainty in the ungerade resonance contribution to the total cross sections. On the other hand, we show that the major contribution to the DEA peak is due to the ${}^2{\mathrm{\Sigma }}_u{}^{+}$ resonance. Results for the total integrated cross sections are in agreement with existing experiments within the uncertainty of the theoretical calculations.

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• Electron & positron scattering
• Interatomic & molecular potentials