Investigating excited electronic states of I2+ and I22+ produced by strong-field ionization using vibrational wave packets

In pump-probe experiments with a femtosecond near-uv laser, a wave packet is launched onto an excited electronic state of I-2(+) through strong field ionization, and starts vibrating in the corresponding potential well. The vibrational wave packet is further ionized by a probe pulse to an excited electronic state of I-2(2+) that dissociates into I2++I0+. Projecting the vibrational wave packet onto the dissociation channel reveals characteristics of both potential curves via the periodic variations in kinetic energy distribution of the dissociating fragments. The experimental results are consistent with theoretical simulations that are sensitive to the shape of the potential curves. We find that the intermediate state in I-2(+) is A(2)Pi(u,3/2) and ionization to this state has an anomalous angular dependence. Moreover, we extract the I2++I0+ potential energy curve and find evidence for a truly bound potential well, in contrast to the metastable ground state potential energy curves.