C 1s → π* excitation in variable size benzene clusters

Abstract

The C 1s -->pi* transition in molecular benzene and benzene clusters is investigated by photoion yields at high energy resolution. The vibrationally resolved band shows the same shape in clusters as in the bare molecule, but it is redshifted by 50 meV in small clusters, i.e. near the threshold of cluster formation. This redshift increases to 70 meV with increasing cluster size. The results are assigned in comparison with ab initio calculations on model structures of dimers, trimers, and tetramers. These indicate that different carbon sites in the molecular moieties give rise to distinct spectral shifts, where carbon sites that are pointing to the pi-system of another molecule show a larger redshift than the other ones. Such structural properties are found in solid benzene, so that the gas-to-solid shift of C 1s -->pi* excited benzene is derived to be a redshift which is of the order of 100-180 meV.

Nucleation of Organic Crystals—A Molecular Perspective

“…From a CNT perspective, this research direction reveals the nature of the building units of the [86,88] 5-fluorouracil (nitromethane/water) molecular modeling yes (exp. XPS studies of core-level binding energies associated with hydrogen bonding and protonation have already been carried out [72][73][74][75][76][77][78]97] and together with previous studies of core-level shifts caused by van der Waals and dipole interactions [98][99][100] have prepared the ground for more detailed structural studies of solute-solvent interactions, self-association, and cluster formation. [94] benzophenone (methanol, toluene) NMR yes [91] diphenylamine (methanol, toluene) NMR yes [91] p-acetanisidide (chloroform) NMR yes [84] isonicotinamide (methanol, nitromethane) FTIR, Raman yes [89] carbamazepine (methanol, chloroform) NMR yes [105,106] nucleus, and the nature of the building units is related to the attachment frequency of the molecules.…”

“…Dielectric spectroscopy is an emerging technique that reveals information about molecular movement during crystallization from the amorphous state, [95,96] whereas spectroscopic methods with soft X-rays, such as XPS and NEXAFS, have been shown to be sensitive to bond lengths, coordination numbers, and the geometric arrangement of coordinating species, as well as the oxidation and charge state of solute species. XPS studies of core-level binding energies associated with hydrogen bonding and protonation have already been carried out [72][73][74][75][76][77][78]97] and together with previous studies of core-level shifts caused by van der Waals and dipole interactions [98][99][100] have prepared the ground for more detailed structural studies of solute-solvent interactions, self-association, and cluster formation.…”

Free clusters studied by core-level spectroscopies

“…Compared to the van der Waals-bonded case of N 2 discussed above, the inter-molecular bonding is stronger for benzene, which is a liquid at NTP. Consequently, the corresponding XAS spectra exhibit somewhat larger, but still small, changes from monomer to cluster than N 2 clusters [104]. The results were assigned in comparison with ab initio calculations on model structures of dimers, trimers, and tetramers.…”

Soft X-ray Absorption Spectroscopy of Liquids for Understanding Chemical Processes in Solution

“…It is known in the previous work that the aromatic π-π interactions cause an energy shift of the π* peak in XAS. [67][68][69] We have also measured C K-edge XAS spectra of benzene clusters in the gas phase, 70 which are formed by an adiabatic gas expansion method, and solid benzene at -193 C, 71 and found that the π* peaks show lower energy shifts compared to those of gas, which is ascribed to different structural properties of clusters compared to the solid. In the present work, we have systematically investigated temperature-dependent changes of ordered structures in liquid benzene by C K-edge XAS with the combination of the MD simulation and inner-shell calculations.…”