Cross sections for the formation of H(n = 2) atom via superexcited states in photoexcitation of methane and ammonia

Formation of hot hydrogen atoms from superexcited states of acetylene

The cross sections for the formation of the H(2p) and H(2s) atoms, σ _2p and σ _2s , respectively, in photoexcitation of C₂H₂ were obtained in an absolute scale for studying formation and decay of superexcited states in the extreme ultraviolet range. Several superexcited states of C₂H₂ including multiply excited states were found in the curve of the σ _2p cross sections as a function of the incident photon energy. The same states seem to contribute to the variation in the σ _2s cross sections as well, which can be ascribed to the non-adiabatic transitions between the 2p and 2s channels. The Σ/Π symmetry-resolved cross sections for the H(2s) atom formation, σ 2 s Σ and σ 2 s Π , were also obtained on an absolute scale. The coupling between the Σ u + 1 and ¹Π _u states was found to be small.