Effects of magnetic field on the 15V 31 344.9 band of CS2 studied by sub-Doppler high-resolution spectroscopy

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Abstract
Effects of an external magnetic field on the excitation spectrum of the 15V 31 344.9 band of the CS2 molecule are measured with sub‐Doppler resolution. New lines are observed to appear near the R(2) and P(4) lines when a magnetic field is applied. These lines are observed to be composed of five components both for the π pump and for the σ pump. From a theoretical analysis, we identify the new lines as transitions to the 3 A 2(A 1−B 1)(v −;12M) levels, which become allowed by Zeemaninteraction with the V 1 B 2(v′;03M) level that is mixed with the 3 A 2(B 2)(v;03M) level by spin–orbit interaction. Variations of energy shifts and intensities with the magnetic field strength are explained quantitatively by this analysis. M‐dependent perturbation and the quenching of fluorescence are observed. The reason why large Zeeman splittings are observed at many lines in the V system of CS2 can be attributed to the spin–orbit interaction between the V 1 B 2(v′;KJM) level and the 3 A 2(B 2)(v;KJM) level combined with the rotational and/or the Zeemaninteractions between 3 A 2(B 2)(v;KJM) level and either 3 A 2(A 1+B 1)(v 0;K±1JM) or 3 A 2(A 1−B 1)(v ±; K±1J±1M) levels which are accidentally close in energy.