VUV absorption spectrum of acetic acid between 6 and 20Â eV

Absorption spectra of acetic acid were measured between 6 and 20 eV at a resolution of 8 meV. Previous measurements had a spectral limit of 11.7 eV. Analysis and band assignment were aided by data from theoretical calculations on valence states and from photoelectron spectroscopy. Valence transitions and nsa′ ← 13a′, npa′ ← 13a′ and nda′ ← 13a′ Rydberg transitions converging to the ground state of CH3COOH+, as well as transitions converging to the first excited state of the ion are discussed and assigned in the spectral region below 12 eV. Our assignments of valence transitions differ in many aspects from those of previous studies. Most of the Rydberg bands have never previously been assigned. Observation, analysis and possible assignments of absorption features between 12 and 20 eV were carried out for the first time. Rydberg bands converging to the higher ionization limits merge to form broad absorption features. Some absorption features in the 14-17 eV region are assigned to two types of valence σ*(C-H) ← σ transitions.