The influence of the ionisation potential on the simulated ion signal from femtosecond pump-probe experiments

Femtosecond pump-probe experiments involving pseudorotational motion on the B state of the sodium trimer are simulated using time-dependent wavepacket calculations. The calculations are carried out in two dimensions, corresponding to the radial and angular pseudorotation modes. The pump and probe lasers are modelled using time-dependent first-order perturbation theory. The ion signal is simulated using two different values of the ionisation potential: the first, 32240 cm−1, is close to an older experimental value; the second, 31363 cm−1, was recently obtained from ZEKE spectra. The relative intensities of different peaks depend strongly on the value of the ionisation potential used. The ion signal calculated using the more recent value for the ionisation potential shows closer agreement with the signal found in the experiments.