The first real-time study on pyridazine in the S1(n,p*) state is presented. The S1 state is found to
dephase with a time constant of 323617 ps at its origin, and the electronic dephasing mechanism
is attributed to the S1– S0 internal conversion. The S1 lifetime is found to decrease rather sharply as
the internal energy increases. The 3s (n21) and 3p (n21) Rydberg states of pyridazine are clearly
identified in angle- and energy-resolved photoelectron images obtained in the (1128)
photoionization scheme, providing their respective term values of 5.6860.03 and 6.2860.04 eV.