Interatomic potentials for Cd, Zn, and Hg from absorption spectra

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Abstract
The absorption coefficient has been measured over a 65 nm range in the red wing of the 213.8 nm line for Zn vapor at 1000 °C. It has also been measured in the blue wing and over a 60 nm range in the red wing of the 228.7 nm line for Cd vapor at five temperatures between 642 and 955 °C and over a 75 nm range in the red wing of the 253.7 nm line for Hg vapor at five temperatures between 460 and 860 °C. These data are analyzed in terms of the statistical theory of broadening. Oscillator strengths of 1.42±0.01 and 1.61±0.06 are obtained for, respectively, the Cd line and the Zn line. Pair potentials for both the ground and lowest excited state are also obtained in all three cases. For Cd this is done assuming no functional form and then assuming Lennard‐Jones potentials. Both methods agree and give a ground state minimum of −47.5 meV at 0.482 nm separation and an excited state minimum of −1.06 eV at 0.410 nm. A functional form is required for the less extensive Zn data and the Lennard‐Jones form leads to a range of possibilities including ground and excited state minima of −56 meV at 0.400 nm and −1.30 eV at 0.330 nm, respectively, which are in fair agreement with the theoretical calculations. For Hg the experiments indicate a single excited state and a ground state with a minimum of −55 meV. Assuming no functional form for the pair potentials, taking the excited state as doubly degenerate, and assuming the transition probability from the ground to excited state is one‐sixth of the free atom value gives points along the ground and excited state potentials that join smoothly with other experimental results and agree well with the calculation of Baylis for the ground state.