No abstract

By using the technique of mass-analyzed threshold ionization spectroscopy, we were able to measure ionization energies of indole−Ar (62505 cm-1), indole−H2O (59433 cm-1), and the indole−benzene (59833 cm-1) complexes, as well as their dissociation energies in the cationic ground state. The dissociation energies in the neutral ground state are calculated from the experimental data. The ionic E 0 = 537 ± 10 cm-1 and neutral dissociation energy D 0 = 451 ± 15 cm-1 of the indole−Ar complex are much smaller than those of the indole−H2O complex; E 0 = 4790 ± 10 cm-1, D 0 = 1632 ± 15 cm-1 and of the indole−C6H6 complex:  E 0 = 4581 ± 10 cm-1, D 0 = 1823 ± 15 cm-1. This demonstrates the van der Waals character of the indole−Ar complex and the hydrogen bonding type in indole−water. Furthermore, we conclude that the indole−benzene complex is hydrogen-bonded with the benzene π-cloud serving as electron donator and indole serving as hydrogen donator.

No abstract

Delayed pulsed field threshold ionization of clusters excited to high long-lived Rydberg states is used to study their dissociation behavior. Benzene–Ar and benzene–Kr dimers are excited by resonance enhanced two-photon ionization to Rydberg levels close to various ionization thresholds. The field ionized threshold ions are monitored and separated from the non-energy-selected ions in a reflecting field mass spectrometer with high mass resolution. The appearance of threshold ions at the daughter ion mass indicates the onset of a dissociation process. Daughter ions are first observed for the 16161(3/2) level of the two investigated dimers. This leads to an upper limit of the dissociation energy of benzene–Ar of 340 cm−1 which is probably higher than the true dissociation energy. For the first time threshold ions are observed for large internal energies of some 5 eV in the core indicating that high Rydberg states maintain their long lifetime even if the core is electronically or vibrationally excited by several eV.

No abstract