Spectroscopy and relaxation kinetics of the perturbed CO(b 3Σ+,v′=0,1,2) and CO(a′ 3Σ+, v′=31–36, 40, and 41) levels and reinterpretation of CO(a′ 3Σ+, v′=34 and 35) formation in the Kr(5s′[1/2])+CO reaction

Abstract

The spectroscopic and kinetic consequences associated with the strong homogeneous interactions between (i) CO(b 3Σ+,v′=0) and CO(a′ 3Σ+, v′=30, 31, and 32), (ii) CO(b 3Σ+,v′=1) and CO(a′ 3Σ+, v′=34, 35, and 36), (iii) CO(b 3Σ+,v′=2) and CO(a′ 3Σ+, v′=40 and 41) levels are evaluated. Mixing of b 3Σ+ character into the a′ 3Σ+ levels reduces the radiative lifetimes of the latter, because the lifetimes of pure b 3Σ+ and a′ 3Σ+ states are approximately 50 ns and 3 μs, respectively. The strength of the interaction changes with rotational level, and the rotational line intensities and the radiative branching to different v″ levels of the CO(a′ 3Σ+–a 3Π) transition are strongly affected. Comparison of high resolution CO(a′, v′=31, 34, and 35) experimental spectra with calculated spectra shows a marked underestimation of the rotational temperature of these CO(a′,v′) levels unless the mixing is explicitly recognized. With benefit of this knowledge, some results from the Kr(5s′[1/2]0)+CO excitation-transfer reaction need to be reinterpreted. Emission spectra for 300 K rotational distributions from CO(b,v′=0, 1, and 2) and CO(a′,v′=30, 31, 34, and 35) were used to obtain vibrational band intensities for comparison with model calculations. Analysis of the pressure and time dependence of the laser-induced fluorescence data permit the electronic relaxation mechanism of the CO(b,v′=0, 1, 2) and CO(a′,v′=31 and 35) levels in He buffer gas to be discussed. The experimental radiative lifetimes of CO(b,v′=0,1,2) were measured as 60±6, 63±4, and 58±4 ns, respectively. The role of the homogeneously perturbed levels in the collisional relaxation mechanism is discussed.