Fig. 1. (a) Photoelectron imaging apparatus; (b) schematic diagram of the femtosecond time resolved photoelectron imaging setup.

Fig. 2. (a) Two color (at time overlap) and one color mass spectra of 2-methlypyrazine at 323 nm pump and 400 nm probe; (b) time-resolved total ion signals of parent ion as a function of delay time between the pump pulse at 323 nm and the probe pulse at 400 nm. The circles are the experimental results, and solid lines are the fitting results.

Fig. 3. Time-resolved photoelectron raw images (shown in the upper row) and BASEX-inverted images (shown in the lower row) at various time delays observed at 323 nm pump and 400 nm probe.

Fig. 4. (a) Photoelectron kinetic energy distributions (PKE) at different time delay; (b) photoelectron kinetic energy distributions at 0 and 92 ps.

Fig. 5. Time-resolved PKE bands intensity as a function of representative delay times.

Fig. 6. (a) The intensity changes of different photoelectronic peaks with 0–4 ps pump- probe time delay; (b) anisotropy parameters of the six rings as a function of pump-probe time delay.

Fig. 7. (a) The intensity changes of different photoelectronic peaks with 105–130 ps pump- probe time delay; (b) anisotropy parameters of the six rings as a function of pump-probe time delay.

Fig. 8. Schematic representation of the excitation and ionization scheme of 2-methlypyrazine using 323 nm pump and 400 nm probe pulses.