Study of cross sections, oscillator strengths, generalized oscillator strengths, and atomiclike character of the molecular orbitals of formaldehyde for inelastic transitions to valence and Rydberg states

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Abstract
Oscillator strengths, generalized oscillator strengths, and cross sections are calculated using Hartree−Fock wavefunctions for spin allowed electronic transitions from the 2b2(n) and 1b1(π) molecular orbitals to the nb2 (n = 3, 4, and 5), nb1 (n = 2 and 3) and na1 (n = 5,⋅⋅⋅,10) Rydberg series, and for the singlet → triplet 2b2) 2b1) transition. The first Born approximation is utilized in the calculation of f (K), and exchange contributions are included in the calculation of the total cross sections with the Born−Ochkur−Rudge modifications. Contour plots illustrating the radial and angular dependence of the orbitals are presented to substantiate the atomiclike character of the nb2 and nb1 orbitals and to demonstrate the mixture of atomiclike states which contribute to the na1 molecular orbitals. The qualitative shape and trends in the occurence of extrema in the generalized oscillator strengths are discussed for transitions to Rydberg series whose excited molecular orbitals possess a given atomiclike character within the same point group symmetry. The oscillator strengths presented agree well with those determined both by electronic scattering techniques and with ultraviolet measurements in all but the π → π* excitation.