Electron-impact excitation of D1Δ←X1Σ+ in carbon monoxide

Abstract

The dipole-forbidden transition of D1delta <-- X1sigma+ of CO has been observed by a fast electron-energy-loss spectrometer at a large scattering angle of 7 degrees and with an energy resolution of 60 meV. The energy levels and the relative intensity distribution of D1delta, v'=9-25 have been determined, most of the results are reported for the first time.

Valence-Shell Excitations of Nitrous Oxide Studied by Fast Electron Impact

“…[19] Thus the transitions of 𝐵 3 Δ, 𝐶 3 Π and 𝐷 3 Σ ± can be neglected for the present fast electron impact. Our previous investigations about the valence-shell excitations of the atoms of Ne, [20] Ar, [21] Kr [22] and the diatomic molecule of O 2 [23] and CO [24] confirm the above theoretical prediction. Therefore, the peak profile parameters of the 𝐵 1 Δ, 𝐶 1 Π and 𝐷 1 Σ + states of nitrous oxide determined by this work at an incident electron energy of 2.5 keV provide the possibility for determining the quantitative differential cross sections at low-energy electron impact in the future.…”

Optically Forbidden Transition of A ′ 3 Δ u ← X 3 Σ g − in Oxygen

“…The reason can be elucidated as follows: For sufficiently fast electron impact, the influence of the incident particle upon an atom or molecule can be regarded as a sudden and small external perturbation, and the probability for the spin-forbidden transition in connection with the electron-exchange effect is negligibly small for fast electron impact. [20] Our previous investigations about the valence-shell excitations of the atoms of He, [21] Ne, [22] Ar, [23] Kr [24] and the diatomic molecule of CO [7] confirm the above theoretical prediction. Thus the transition of 𝑐 1 Σ − 𝑢 ← 𝑋 3 Σ − 𝑔 can be neglected for the present fast electron impact.…”

“…However, because of the strong Rydberg-valence interaction, the valence-shell excitations of oxygen are dominated by the dissociation continuum states such as the well-known Schumann-Runge continuum, [5,6] which is different from the dominative discrete energy levels of other diatomic molecules such as CO, H 2 , and N 2 . [4,7] Even now the calculation for the peak profiles of the dissociation continuum states of oxygen is a challenge to the theorists, even for the dipole-allowed states. [6] The Herzberg pseudocontinuum, which is the dipole-forbidden transition from the ground state of the (.…”

Selection rules for electric multipole transition of diatomic molecule in scattering experiments

“…For example, D 1 ∆ ← X 1 Σ + of CO is an electric dipole-forbidden transition, but it is the electric quadrupoleand octupole-allowed ones. In the fast electron energy loss spectrum of CO at a large scattering angle of 7 • is observed, [26] while it is absent at 0 • . [27] This is in accordance with the theoretical predictions.…”