Photoionization of small sodium-doped acetic acid clusters

Abstract

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.

Atmospheric processes on ice nanoparticles in molecular beams

“…This technique has been developed in Buck's laboratory (Bobbert et al, 2002; Zeuch and Buck, 2013) and used for size resolved infrared spectroscopy of large clusters (Forck et al, 2010; 2012; Pradzynski et al, 2012). Yoder et al (2011) also proposed it as a general method for atmospheric aerosol detection and sizing (see also Forysinski et al, 2011). The experiments are based on the phenomena of solvated electron generation from Na in water clusters.…”

UV Photoionization of Sodium‐Doped Formic Acid Clusters

“…In the case of small sodium-doped acetic acid clusters, analysed by Forysinski et al, [44] the PCET phenomenon was not observed, but large reorganization energies (> 1.0 eV) for complexes containing more than one FmA monomer have also been found. Thus, both FmAs show the neutral electron configuration and their lone pair electrons on the carbonyl groups make strong electrostatic interactions with the ionized sodium atom.…”

Mass spectrometry of aerosol particle analogues in molecular beam experiments

“…Apart from water, other clusters were ionized by this method including even Ar clusters, where obviously no solvated electron is formed and simply the relatively weakly bound electron from Na atom is detached with ∼5.1 eV energy photons . Later on this method has been proposed as a “ sizer for weakly bound ultrafine aerosol particles ,” and several other homogeneous clusters were investigated by this method in Signorell's group …”

“…There have been methods proposed for cluster ionization (some will be discussed below in more details) that were claimed to be fragmentation-free. For example, sodium doping worked very well for water and some other homogeneous clusters, 50,58,98,135,152,[158][159][160] but cannot be applied generally, as discussed below. Recently, near threshold VUV-photoionization has been shown to give good results for some clusters.…”

“…165 Later on this method has been proposed as a "sizer for weakly bound ultrafine aerosol particles," 135,160 and several other homogeneous clusters were investigated by this method in Signorell's group. 50,152,159 In relevance to PSCs in atmospheric chemistry, we have investigated the mixed nitric acid-water clusters implementing the NaPI method. 34 To our surprise, these clusters could not be detected by the NaPI at all.…”