Determination of time scales for charge-transfer screening in physisorbed molecules

Using photoionization, photoabsorption, and deexcitation spectroscopies, the dynamics of the N 1s core-hole states for N₂ physisorbed on graphite has been investigated. In the photoemission spectrum only the ionic 1s^-1 state is observed. The Auger spectrum shows decay from both this ionic and a neutral 1s^-11πg intermediate state created by charge transfer from the substrate. The neutralization occurs with a characteristic time τCT=9×{}10^-15 s. The coupling with the substrate is weak, preserving the gas-phase triplet-singlet splitting of the neutral intermediate state.