Electron-impact vibrational excitation of isocyanic acid HNCO

In a combined experimental and theoretical study, we probe the vibrational excitation of isocyanic acid induced by electron impact in the energy range up to 5 eV. Experimentally, we report differential elastic and vibrationally inelastic cross sections at the scattering angle of ${135}^{\ensuremath{\circ}}$. Theoretically, we characterize the involved resonant states using a regularized analytical continuation method. We also apply a nonlocal resonance model to calculate cross sections for vibrational mode that involves the N-H stretching motion. The model reproduces all the features observed in the experiment: efficient excitation at threshold, sharp cusps in the excitation functions, and the formation of an ${A}^{\ensuremath{'}}$ shape resonance. There is a second $({A}^{\ensuremath{'}\ensuremath{'}})$ resonance visible in the spectra; however, it excites only selected vibrational modes. The origins of this selectivity are discussed.