Fluorescence lifetimes and Zeeman quantum beats of single rotational levels in 3B2 carbon disulfide

Abstract

The lowest observed triplet state of carbon disulfide, the R ³B₂ state, was directly excited using a pulsed, narrow bandwidth dye laser (0.05 cm⁻¹). The first reported collision‐free lifetimes of this state of CS₂ were obtained, and the changes in lifetime for single rotational and vibrational levels were observed. The effect of rotation and vibration on the lifetimes indicates that the R ³B₂ state has strong spin‐orbital coupling with the higher lying V ¹B₂ state, which gives the R ³B₂ state such short lifetimes (2–5 μs) for a triplet state. A magnetic field was observed to have no effect on the lifetimes, which is consistent with this strong spin‐orbital coupling scheme. Zeeman quantum beats were observed on the fluoresence decay curves in a magnetic field. Beat frequencies were obtained as a function of magnetic field strength to obtain permanent magnetic dipole moments for the R ³B₂ state vibrational levels. The magnetic dipole moments were found to be independent of rotational angular momentum (N dependence) indicating a strong spin‐orbital coupling, consistent with the lifetime data. The collisional depolarization rate was qualitatively observed to be competitive with and slightly faster than electronic quenching.