Search for: All records

We probe the separation of ligands from iron tetracarbonyl methyl acrylate (Fe(CO)₄(C₄H₆O₂) or Fe(CO)₄MA) induced by the interaction with free electrons. The motivation comes from the possible use of this molecule as a nanofabrication precursor and from the corresponding need to understand its elementary reactions fundamental to the electron-induced deposition. We utilize two complementary electron collision setups and support the interpretation of data by quantum chemical calculations. This way, both the dissociative ionization and dissociative electron attachment fragmentation channels are characterized. Considerable differences in the degree of precursor fragmentation in these two channels are observed. Interesting differences also appear when this precursor is compared to structurally similar iron pentacarbonyl. The present findings shed light on the recent electron-induced chemistry of Fe(CO)₄MA on a surface under ultrahigh vacuum. 

We report a combined experimental and theoretical investigation of electron–molecule interactions using pyrrole as a model system. Experimental two-dimensional electron energy loss spectra (EELS) encode information about the vibrational states of the molecule as well as the position and structure of electronic resonances. The calculations using complex-valued extensions of equation-of-motion coupled-cluster theory (based on non-Hermitian quantum mechanics) facilitate the assignment of all major EELS features. We confirm the two previously described π resonances at about 2.5 and 3.5 eV (the calculations place these two states at 2.92 and 3.53 eV vertically and 2.63 and 3.27 eV adiabatically). The calculations also predict a low-lying resonance at 0.46 eV, which has a mixed character—of a dipole-bound state and σ* type. This resonance becomes stabilized at one quanta of the NH excitation, giving rise to the sharp feature at 0.9 eV in the corresponding EELS. Calculations of Franck–Condon factors explain the observed variations in the vibrational excitation patterns. The ability of theory to describe EELS provides a concrete illustration of the utility of non-Hermitian quantum chemistry, which extends such important concepts as potential energy surfaces and molecular orbitals to states embedded in the continuum.