Journal of Chemical Physics, Vol.113, No.21, 9532-9539, 2000
Discovery of benzene cation in a very long-lived excited electronic state
Presence of benzene cation in a long-lived excited electronic state at similar to2.3 eV above the ground state was found through photodissociation kinetics land charge exchange ionization mass spectrometry. The lifetime of this state seems to be longer than 10 mus, maybe much longer. The experimental energy level of this state suggests that (B) over tilde E-2(2g) is the best candidate. The radiative transition from the latter state to the ground State, (B) over tilde (2)E(2)g-->(X) over tilde E-2(1g), is electric dipole forbidden. Then, a very long lifetime requires an inefficient radiationless decay of the state. This is in contrast with the very fast decay proposed previously to account for the lack of fluorescence from the (B) over tilde E-2(2), state. The present finding opens the possibility of studying a new excited state chemistry.