Vibrationally resolved photoemissions of N (CΠ → BΠ) and CO (bΣ → aΠ) by low-energy electron impacts.

Vibrationally resolved photoemission spectra of the electronic-state transitions CΠ → BΠ of N and bΣ → aΠ of CO following low-energy electron impacts are measured with a crossed-beam experimental arrangement. The absolute cross sections of CΠ (ν') → BΠ (ν″) of N are presented for the vibrational state-to-state transitions (ν',ν″) = (0,0), (0,1), (1,0), (1,2), and (2,1). The excitation cross sections of the metastable state CΠ of N show the maxima at the electron-impact energies 14.10 (ν' = 0) eV and 14.50 (ν' = 1) eV, which are potentially related to the core-excited vibrational Feshbach resonant state Σ of N formed by electron attachment. The absolute cross sections of bΣ (ν' = 0) → aΠ (ν″ = 0, 1, 2, 3, 4) of CO are given by the calibrations with those of N measured in this work. Besides the maximum excitation cross section 5.85 × 10 cm at 10.74 eV of the CO bΣ (ν' = 0) state, some fine structures on the excitation function profile are attributed to different shapes and Feshbach resonant states of CO formed by electron attachment, while the others arise from the direct electron-impact excitation. Some discrepancies, particularly for N, between the present data and the results available in the literature studies arise from different experimental techniques and data-processing procedures. Furthermore, contributions of physical processes such as wave-packet evolution and non-Franck-Condon dynamics are highlighted here.