The Born–Oppenheimer equilibrium bond distance of GeO from millimetre- and submillimetre-wave spectra and quantum-chemical calculations

Abstract

The millimetre- and submillimetre-wave spectra of the five common isotopologues of Ge¹⁶O in their electronic and vibrational ground state have been recorded in the spectral region 115–732 GHz; for ⁷⁴Ge¹⁶O, the rotational spectrum in the v = 1 state has been detected as well. Exploiting the high precision of the measurements, the Born–Oppenheimer breakdown parameter Δ^Ge₀₁ could be determined from a Dunham analysis of the spectral data, whereas Δ^O₀₁ was obtained from quantum-chemical calculations, because of the lack of high-precision measurements for the Ge¹⁸O isotopologues. From the rotational equilibrium constant, the Born–Oppenheimer equilibrium distance of GeO could be determined.

Keywords:

• rotational spectrum
• equilibrium bond distance
• Born–Oppenheimer breakdown
• quantum-chemical calculations

Notes

1. Thermally Pulsating Asymptotic Giant Branch stars.

2. Natural germanium is composed of ⁷⁰Ge (20.5%), ⁷²Ge (27.4%), ⁷³Ge (7.8%), ⁷⁴Ge (36.5%) and ⁷⁶Ge (7.8%).

3. N_Ah = 3.990 312 7176(28) × 10⁻¹⁰ J s mol⁻¹ with a relative standard uncertainty of 7.0 × 10⁻¹⁰, from the recommended fundamental constants listing CODATA 2010 [4]

4. Value determined from a fit to a power series in of the data from both Ref. [9] and Ref. [10].

Additional information

Funding

In Bologna, this work was supported by the Ministero dell’Istruzione, dell’Università e della Ricerca (PRIN 2012 funds, project STAR) [grant number 20129ZFHFE] and the University of Bologna (RFO funds). In Mainz, this work was supported by the Deutsche Forschungsgemeinschaft [grant number DFG GA-370/5-1] and the Fonds der Chemischen Industrie.