Partial ion yield study of gas-phase acetamide and acetic acid clusters
Clusters of a variety of molecules are receiving increasing attention due to thier unique size-dependent physicochemical properties in the transition from gas to condensed phase and wide number of possible applications in electronics, biomedicine, and materials science. Theoretical and experimental investigations of molecular clusters structure and properties is an attractive growing field of research.
We used vacuum ultraviolet (VUV) photoionization mass spectroscopy and partial ion yield (PIY) technique to study gas-phase homogeneous clusters of acetamide and acetic acid molecules produced by the supersonic expansion source in order to explore their electronic properties as a function of their size. We were able to produce acetamide clusters containing up to eight molecules (Fig. 1) and acetic acid clusters containing up to seven molecules. From the PIY measurements, PIY curves were extracted showing yield of ions as a function of photon energy. Analyzing the slopes of these curves, appearance energies of acetic acid clusters up to tetramer and acetamide clusters up to hexamer were experimentally determined.
The obtained results allow to learn novel information about dissociation patterns and fragmentation pathways of the acetamide and acetic acid clusters followed by valence region ionization. Comparison of these two compounds can specifically give an answer concerning the role of the -NH2 or -OH functional groups on the energetic properties of the acetic acid or acetic acid amide clusters. To conclude, the goal of this scientific mission was achieved – data analysis was finalized and writing the article about homogeneous acetamide clusters PIY study has begun.
Figure 1. Positive ion time of flight spectrum of acetamide clusters measured at hʋ = 9.8 eV. The numbers correspond to the amount of acetamide molecules contained in a protonated cluster.