Spectroscopic investigation of the double-minimum21Σu+state of the potassium dimer

Abstract

The double-minimum $2{}^{1}{\ensuremath{\Sigma}}_{u}^{+}$ state was investigated in ${}^{39}{\mathrm{K}}_{2}$ and ${}^{39}{\mathrm{K}}^{41}\mathrm{K}$ molecules by analyzing spectra of the $2{}^{1}{\ensuremath{\Sigma}}_{u}^{+}\ensuremath{\leftarrow}X{}^{1}{\ensuremath{\Sigma}}_{g}^{+}$ band system, simplified by polarization labeling. A wide range of rovibrational levels 21\ensuremath{\leqslant}v\ensuremath{\leqslant}97, 18\ensuremath{\leqslant}J\ensuremath{\leqslant}159 was observed. By using the inverted perturbation approach to construct the exotic potential-energy curve, an accurate, isotopically consistent description of the $2{}^{1}{\ensuremath{\Sigma}}_{u}^{+}$ state has been obtained.