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

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 3A2(A1−B1)(v−;12M) levels, which become allowed by Zeeman interaction with the V 1B2(v′;03M) level that is mixed with the 3A2(B2)(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 1B2(v′;KJM) level and the 3A2(B2)(v;KJM) level combined with the rotational and/or the Zeeman interactions between 3A2(B2)(v;KJM) level and either 3A2(A1+B1)(v0;K±1JM) or 3A2(A1−B1)(v±; K±1J±1M) levels which are accidentally close in energy.