Adiabatic ionization potential of acetic acid and torsional dynamics of its cation

Pulsed-field-ionization zero-kinetic-energy photoelectron spectroscopy and supersonic cooling are used to investigate the CH3 torsional dynamics of the acetic acid cation and to determine an accurate value for the first adiabatic ionization potential of acetic acid (IP=85 912±5 cm−1), which has been the subject of debates for more than 40 yr. A doubling of the torsional barrier upon ionization is due to a significant shortening of the C–C bond and reduces the tunneling efficiency by an order of magnitude.ISSN:0021-9606ISSN:1089-769

Photoionization of small sodium-doped acetic acid clusters

The uptake of sodium and the fragmentation before and after “soft” photoionization with ultraviolet light are investigated for small acetic acid clusters. The acetic acid clusters are generated in a supersonic expansion and ionized with ultraviolet light after doping with sodium in a pick-up chamber. The composition of the bare acetic acid clusters in the molecular beam is determined independently from complementary photoionization experiments using extreme ultraviolet light. The experimental results are analyzed with the help of density functional calculations for energetics and statistical adiabatic channel calculations for fragmentation kinetics. The study demonstrates that the detected ions originate from fragmentation in the neutral as well as in the ionic state, and in particular that the fragmentation pathway strongly depends on the cluster size.ISSN:0021-9606ISSN:1089-769