On the validity of the equivalent cores approximation for computing X-ray photoemission and photoabsorption spectral bands

• We evaluate the performance of the equivalent cores (Z + 1) approximation for computing core photoemission and photoabsorption spectral bands versus full self-consistent field optimizations. Franck-Condon factors are obtained using the linear coupling model with the multi-dimensional vibronic coupling constants computed from analytical calculations of the ground state frequencies and normal coordinates, and excited state energy gradients evaluated at the ground state equilibrium geometry. We use carbon monoxide, formaldehyde, chloromethanes and some monosubstituted benzenes for the purpose. Considering other inherent approximations in the calculations, we find that the equivalent core model works well for band shapes and comparatively better for excitations of strong modes and ionization of deeper core levels. The approximation also works somewhat better for photoemission than for discrete photoexcitation.

Subject headings

NATURVETENSKAP  -- Kemi -- Fysikalisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Physical Chemistry (hsv//eng)

NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

Keyword

correlated molecular calculations

electron-binding energies

gaussian-basis sets

vibrational structure

photoelectron-spectroscopy

abinitio calculations

restricted-step

wave-functions

row atoms

shifts

Physical chemistry

Fysikalisk kemi

Physics

Fysik

Publication and Content Type

ref (subject category)

art (subject category)