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ABSTRACT
Based on the recently developed implementation of the full semi-classical field–matter interaction operator, we present a numerically accurate yet efficient scheme to perform rotational averaging of linear absorption spectra beyond the electric-dipole approximation. This allows for a gauge-origin independent determination of UV/vis and X-ray absorption spectra for randomly oriented systems such as multilayers, liquids, and gas phase samples. The approach is illustrated by the determination of spectral intensities of electric-dipole allowed π → π* transitions and electric-dipole forbidden n → π* transitions in the UV–vis region of the spectrum as well as electric-dipole forbidden 1s → 3d transitions in the X-ray region of the spectrum. The employed Lebedev quadrature scheme shows very fast convergence with respect to the number of symmetry-independent quadrature points – in all considered cases, the oscillator strengths for the randomly oriented systems are fully converged with use of only seven quadrature points.
Acknowledgments
It is our great pleasure to dedicate this paper to the 60th anniversary of Prof. Hans Jørgen Aa. Jensen. His outstanding scientific contributions in general and his long-term commitment to the Dalton and DIRAC projects in particular are both of great value to us all. We are very grateful for his sharing of knowledge and scientific guidance as well as for being a dear friend. The authors thank Prof. Christoph Jacob for kindly providing the structures of ferrocene and vinylferrocene.
Disclosure statement
No potential conflict of interest was reported by the authors.