Abstract
Ab initio calculations of the coupled cluster and spin–orbit configuration type, in conjunction with a small-core pseudopotential for the mercury atom, have been employed to construct near-equilibrium potential energy and electric dipole moment functions for HgH2. On that basis, rovibrational term energies and wavefunctions as well as transition dipole moments, absolute IR intensities and Einstein coefficients of spontaneous emission have been calculated variationally. Throughout, excellent agreement is obtained with recent experimental data from Fourier transform infrared emission spectroscopy. The gas-phase wavenumbers of the symmetric stretching and the bending vibrations of 202HgH2 and 202HgD2 (in parentheses) are predicted to be 2012.3 (1442.8) cm−1 and 784.3 (564.1) cm−1, respectively. Various predictions are made for 202HgHD, for which no high-resolution spectra have yet been published.
Highlights
The existence of solid mercury dihydride (HgH2) has been known for more than half a century [1, 2], it was only recently that molecular HgH2 could be investigated by means of highresolution spectroscopy [3, 4]
Higher accuracy is achieved in the present calculations by the following means: a) use of a coupled cluster variant accounting for connected triple substitutions, b) considerably larger basis sets than used in the earlier work, and c) the use of a modern pseudopotential for the mercury atom as well as explicit consideration of spin-orbit interaction
High-level ab initio calculations of the coupled cluster (CC) and spin-orbit configuration interaction (SO-CI) type have been performed for the title molecule
Summary
The existence of solid mercury dihydride (HgH2) has been known for more than half a century [1, 2], it was only recently that molecular HgH2 could be investigated by means of highresolution spectroscopy [3, 4]. HgH2, HgD2, allowing a wealth of spectroscopic constants to be determined with high precision. This material provides an almost ideal testing ground for high-level quantum chemical calculations, but still leaves much room for various predictions. Davidson’s correction (termed MRCI+Q) was employed to approximately account for the effects of ev higher-order substitutions and the mercury atom was described by means of a pseudopotential (PP). Higher accuracy is achieved in the present calculations by the following means: a) use of a coupled cluster variant accounting for connected triple substitutions 9 because of its singlereference character), b) considerably larger basis sets than used in the earlier work, and c) the use of a modern pseudopotential for the mercury atom as well as explicit consideration of spin-orbit interaction Higher accuracy is achieved in the present calculations by the following means: a) use of a coupled cluster variant accounting for connected triple substitutions ( limited in application compared to ref. 9 because of its singlereference character), b) considerably larger basis sets than used in the earlier work, and c) the use of a modern pseudopotential for the mercury atom as well as explicit consideration of spin-orbit interaction
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