Spectroscopic and Theoretical Study of the Weakly Bound H2−HCCCN Dimer

Ab initio potential energy surface and microwave spectra for the H2-HCCCN complex

We present a four-dimensional ab initio potential energy surface of the H₂-HCCCN complex at the coupled-cluster singles and doubles with noniterative inclusion of connected triples [CCSD(T)]-F12 level with a large basis set including an additional set of bond functions. The artificial neural networks method was extended to fit the intermolecular potential energy surface. The complex has a planar linear global minimum with the well depth of 199.366 cm^-1 located at R = 5.09 Å, φ = 0°, θ₁ = 0°, and θ₂ = 180°. An additional planar local minimum is also found with a depth of 175.579 cm^-1 that is located at R = 3.37 Å, φ = 0°, θ₁ = 110°, and θ₂ = 104°. The radial discrete variable representation/angular finite basis representation and the Lanczos algorithm were employed to calculate the rovibrational energy levels for four species of H₂-HCCCN (pH₂-HCCCN, oH₂-HCCCN, pD₂-HCCCN, and oD₂-HCCCN). The rotational frequencies and spectroscopic parameters were also determined for four complexes, which agree well with the experimental values.

The covalent interaction between dihydrogen and gold: A rotational spectroscopic study of H2-AuCl

The pure rotational transitions of H2-AuCl have been measured using a pulsed-jet cavity Fourier transform microwave spectrometer equipped with a laser ablation source. The structure was found to be T-shaped, with the H-H bond interacting with the gold atom. Both 35Cl and 37Cl isotopologues have been measured for both ortho and para states of H2. Rotational constants, quartic centrifugal distortion constants, and nuclear quadrupole coupling constants for gold and chlorine have been determined. The use of the nuclear spin-nuclear spin interaction terms Daa, Dbb, and Dcc for H2 were required to fit the ortho state of hydrogen, as well as a nuclear-spin rotation constant Caa. The values of the nuclear quadrupole coupling constant of gold are χaa=-817.9929(35) MHz, χbb=504.0(27) MHz, and χcc=314.0(27). This is large compared to the eQq of AuCl, 9.63 312(13) MHz, which indicates a strong, covalent interaction between gold and dihydrogen.