Photofragmentation of small gas-phase acetamide clusters (CH₃CONH₂)_n (n
≤ 10) produced by a supersonic expansion source has been studied using
time-of-flight ion mass spectroscopy combined with tunable
vacuum-ultraviolet (VUV) synchrotron radiation. Fragmentation channels
of acetamide clusters under VUV photoionization resulting in protonated
and ammoniated clusters formation
were identified with the discussion about the preceding intramolecular
rearrangements. Acetamide-2,2,2-d3 clusters were also studied in an
experiment with a gas discharge lamp as a VUV light source; comparison
with the main experiment gave insights into the mechanism of formation of protonated acetamide clusters, indicating that proton transfer
from amino group plays a dominant role in that process. Geometry of the
acetamide dimer was discussed and the most stable arrangement was
concluded to be achieved when subunits of the dimer are connected via
two N—H⋯O —C hydrogen bonds. Also, the influence of the photon energy on the stability of the clusters and their fragmentation channels has been examined.