Infrared emission spectra and equilibrium bond lengths of gaseous ZnH2 and ZnD2Electronic supplementary information (ESI) available: A complete list of the observed line positions and the outputs of least-squares fitting program (Tables S1–S13). See http://dx.doi.org/10.1039/b507539d

Abstract

A detailed analysis of the high resolution infrared emission spectra of gaseous ZnH₂ and ZnD₂ in the 800–2200 cm⁻¹ spectral range is presented. The ν₃ antisymmetric stretching fundamental bands of ⁶⁴ZnH₂, ⁶⁶ZnH₂, ⁶⁷ZnH₂, ⁶⁸ZnH₂, ⁶⁴ZnD₂, ⁶⁶ZnD₂ and ⁶⁸ZnD₂, as well as several hot bands involving ν₁, ν₂ and ν₃ were rotationally analyzed, and spectroscopic constants were obtained. Rotational l-type doubling and l-type resonance, local perturbations, and Fermi resonances were observed in the vibration–rotation bands of both ZnH₂ and ZnD₂, and equilibrium vibrational frequencies (ω₁, ω₂ and ω₃) were estimated. Using the rotational constants of the 000, 100, 01¹0 and 001 vibrational levels, the equilibrium rotational constants (B_e) of ⁶⁴ZnH₂ and ⁶⁴ZnD₂ were determined to be 3.600 269(31) cm⁻¹ and 1.801 985(25) cm⁻¹, respectively, and the associated equilibrium bond lengths (r_e) are 1.524 13(1) Å and 1.523 94(1) Å, respectively. The difference between the r_e values of ⁶⁴ZnH₂ and ⁶⁴ZnD₂ is about 0.01%, and is mainly due to the breakdown of the Born–Oppenheimer approximation.