Separation of ionization and subsequent electronic excitation for formation of electronically excited ethanol cation in intense laser fields

Ionization and subsequent electronic excitation occurring within the same laser pulse (400 nm, 96 fs, 1.3 similar to 18 TW cm(-2)) are separately investigated by measuring in coincidence an electron and a product ion produced from C(2)H(5)OH. It is revealed that the nascent population in the electronically excited C(2)H(5)OH(+) prepared by the ionization decreases as the laser intensity increases, while the subsequent electronic excitation is enhanced through the resonant electronic transitions. Ionization and electronic excitation mechanisms are described based on the electronic-state distributions of C(2)H(5)OH(+).