POLARIZATION LABELLING SPECTROSCOPY OF $3^{1}\Pi_{u}-X^{1}\Sigma_{g}^{+}$ AND $3{^{1}}\Sigma^{+}_{u}-$ TRANSITIONS IN $K_{2}$.

Abstract

Polarization labelling spectroscopy was applied to study excited states of $K_{2}$ lying in the energy range $23800 - 25800 cm^{-1}$ above the bottom of the ground state. The two observed states were identified as $3{^{1}}\Pi_{u}(4^{2}S+5^{2}P)$ and $3^{1}\Sigma^{+}_{u}(4^{2}S+3^{2}D)$. Molecular constants were derived for both states from a Dunham expansion.