Magnetic field effect on the H2CS fluorescence from the first excited singlet state

Fluorescence intensity in thioformaldehyde vapors (H2CS), excited to the à 1A2 different vibronic levels of the à 1A2←X 1A1 transition, were measured as a function of an external magnetic field. On excitation to these levels, dynamics in zero and nonzero field may be described in the small-molecule limit, with fluorescence exhibiting an almost exponential decay. A magnetic field changes the integrated intensity and decay lifetime of the thioformaldehyde fluorescence induced from different vibronic levels of the à 1A2 state. We found that the magnetic field effect grows at lower gas pressures. The measured field dependences of the magnetic field effect can be fitted using field-saturated functions. The measured data were explained by the indirect mechanism theory (nuclear-spin and electron-spin decoupling mechanism).