Characteristic distributions of negatively charged N-monosubstituted amide clusters generated by electron attachment in supersonic expansions

Effects of Alkyl Groups on Excess-Electron Binding to Small-Sized Secondary Amide Clusters: A Combined Experimental and Computational Study

“…After that, for several secondary amides, our group succeeded in observation of lager sizes up to n = 30 generated by slow electron attachment in the collisional region of supersonic jets. 20 We found a remarkable pattern in the cluster size distributions with prominent magic numbers, which display an unexpected similarity to that of water cluster anions. 21−23 The first magic number is n = 2 in common, because electron binding energy of the monomer anion is too low for the stationary presence in the ionized jets.…”

“…They determined the electron binding energy of the NMF monomer anion to be 15.7 meV by a sharp resonance of the principal quantum number in the RET process, but they could not measure that for the dimer anion because the yield shows a gentle dependence on the Rydberg quantum number. After that, for several secondary amides, our group succeeded in observation of lager sizes up to n = 30 generated by slow electron attachment in the collisional region of supersonic jets . We found a remarkable pattern in the cluster size distributions with prominent magic numbers, which display an unexpected similarity to that of water cluster anions. − The first magic number is n = 2 in common, because electron binding energy of the monomer anion is too low for the stationary presence in the ionized jets.…”

“…The present experimental and computational findings seem to be incompatible with the previously reported trend in formation efficiency of the trimer anions. 20 We infer from the nature of dipole-bound anions that the cluster-size distributions in the mass spectra are affected by isomeric structures of the neutral clusters prior to the electron attachment. For the case of water clusters, 21−23 the neutral trimer forms a cyclic structure to reduce the total of dipole moment, resulting in the absence from the anionic mass spectrum.…”

Electron localization in negatively charged formamide clusters studied by photodetachment spectroscopy

“…Relative photodetachment cross-section measurements were carried out at Tohoku University utilizing a reflectron type mass spectrometer described elsewhere. 28 It is newly equipped with an electron detector placed nearby the photo-interaction region, where photodetached electrons are repelled to a MCP by a À10 V pulse of 1 ms temporal width. A Nd:YAG laserpumped OPO system (GWU-Lasertechnik, VisIR2) was used for the generation of 0.6-2.9 eV light pulses.…”

“…The maximum intensity always appears around n ¼ 9, of which uniqueness in photoelectron spectrum will be shown later, and a smooth decline after that was observed in contrast with jaggy or undulated mass spectra for cluster anions of N-monoalkyl amides. 28 Injection of high-energy electrons into the collision region of a supersonic jet disturbs the cooling process leading to increase the beam temperature to a certain extent. Successive nucleation and evaporative cooling might follow the electron capture of the neutral clusters before the jet is fully expanded.…”