Rotational analysis and isotopic effects in the [formula omitted] system for the [formula omitted] cation

Abstract

The Doppler-limited absorption spectrum of the O2+18 cation was observed using a Ti–Sapphire laser system (in region of 12060–12800cm−1) by optical heterodyne velocity modulation absorption spectroscopy. Precise molecular constants (Bυ, Dυ, pυ, qυ, γυ) were obtained for the involved levels by fitting spectral lines of (3, 20) and (4, 21) bands in the Second Negative system (A2Πu–X2Πg) using a nonlinear least-squares fitting procedure with the standard Hamiltonians. The vibrational assignment was based on the isotopic effect. More detailed isotopic effects on the molecular constants were discussed as well.