Intersystem Crossing of 2-Methlypyrazine Studied by Femtosecond Photoelectron Imaging

2-methylpyrazine was excited to the high vibrational dynamics of the S(1) state with 260 nm femtosecond laser light, and the evolution of the excited state was probed with 400 nm light. Because it was unstable, the S(1) state decayed via intersystem crossing to the triplet state T(1), and it may have decayed to the ground state S(0) via internal conversion. S(1)-to-T(1) intersystem crossing was observed by combining time-resolved mass spectrometry and time-resolved photoelectron spectroscopy. The crossover time scale was 23 ps. Rydberg states were identified, and the photoelectron spectral and angular distributions indicated accidental resonances of the S(1) and T(1) states with the 3s and 3p Rydberg states, respectively, during ionization.