The first real-time study on pyridazine in the S-1(n, pi*) state is presented. The S-1 state is found to dephase with a time constant of 323 +/- 17 ps at its origin, and the electronic dephasing mechanism is attributed to the S-1-S-0 internal conversion. The S-1 lifetime is found to decrease rather sharply as the internal energy increases. The 3s (n(-1)) and 3p (n(-1)) Rydberg states of pyridazine are clearly identified in angle- and energy-resolved photoelectron images obtained in the (1 + 2') photoionization scheme, providing their respective term values of 5.68 +/- 0.03 and 6.28 +/- 0.04 eV. (C) 2003 American Institute of Physics.