Spectrum of the Molecular Eigenstates of Pyrazine

The molecular eigenstate spectrum belonging to the P and R branches of the 1B3u (0-0) electronic transition of pyrazine-h4 was recorded with a 200 kHz wide laser in a supersonic nozzle at a temperature of ≈1 K. The square of the Fourier transform of the amplitude spectrum yields the quantum beats in the fluorescence decay that have been reported before.