Emission spectrum of rare gas dimers in the vacuum UV region. II. Rotational analysis of band system I of Ar2

Abstract

The emission spectrum of Ar₂ excited by a Tesla discharge has been photographed at high resolution in the region 1073.5–1081.5 Å by 6.65 m spectrograph. Experimental conditions were chosen to produce only the band system emitted in the transition from the lowest excited state to the ground state. Rotational analyses of several bands indicate that the coupling scheme in the lowest excited state is closer to Hund–Mulliken case b than to case c, so that the excited state symmetry may be assigned approximately as ³Σ⁺_u rather than 1_u, 0⁻_u. Rotational constants obtained for seven high‐lying emitting levels with consecutively decreasing vibrational quantum numbers range from 0.073 to 0.105 cm⁻¹. An attempt has been made to use spectroscopic results to depict the shapes and positions of the long range portions of the potential curves of the first two excited states (³Σ⁺_u and ¹Σ⁺_u) of Ar₂ relative to each other and to that of the ground state X ¹Σ⁺_g.