Picosecond excitation of jet-cooled pyrazine: magnetic field effects on the fluorescence decay and quantum beats

Quantum beats and fluorescence decays of the vibrationless S_1 state of jet-cooled pyrazine have been studied as a function of magnetic field. Fourier analysis of the modulated portions of these decays has yielded results which are consistent with first- and second-order Zeeman effects occurring in the excited state. An increase in the number of triplets states effectively coupled to the singlet manifold with increasing magnetic field is discussed in terms of Zeeman interactions.