Potassium ground state scattering parameters and Born-Oppenheimer potentials from molecular spectroscopy

• Published in: arXiv.org 2008-04
• Main Authors: Falke, Stephan, Knoeckel, Horst, Friebe, Jan, Riedmann, Matthias, Tiemann, Eberhard, Lisdat, Christian
• Format: Article
• Language: English
• Subjects: Asymptotic methods; Born-Oppenheimer approximation; Collimation; Collisions; Energy gap; Ground state; Molecular spectroscopy; Particle beams; Scattering
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.0804.2949

We present precision measurements with MHz uncertainty of the energy gap between asymptotic and well bound levels in the electronic ground state X \(^1\Sigma_{\mathrm{g}}^+\) of the \(^{39}\)K\(_2\) molecule. The molecules are prepared in a highly collimated particle beam and are interrogated in a \(\Lambda\)-type excitation scheme of optical transitions to long range levels close to the asymptote of the ground state, using the electronically excited state A \(^1\Sigma^+_{\rm u}\) as intermediate one. The transition frequencies are measured either by comparison with I\(_2\) lines or by absolute measurements using a fs-frequency comb. The determined level energies were used together with Feshbach resonances from cold collisions of \(^{39}\)K and \(^{40}\)K reported from other authors to fit new ground state potentials. Precise scattering lengths are determined and tests of the validity of the Born-Oppenheimer approximation for the description of cold collisions at this level of precision are performed.