Core Excitation, Specific Dissociation, and the Effect of the Size of Aromatic Molecules Connected to Oxygen: Phenyl Ether and 1,3-Diphenoxybenzene

Abstract

Near-edge X-ray absorption fine structure (NEXAFS) spectra of phenyl ether at the carbon K-edge and 1,3-diphenoxybenzene at both the carbon and oxygen K-edges were measured in the total ion yield mode using X-rays from a synchrotron and a reflectron time-of-flight mass spectrometer. Time-dependent density functional theory was adopted to calculate the carbon and oxygen K-edge NEXAFS spectra of phenol, phenyl ether, and 1,3-diphenoxybenzene. The assignments and a comparison of the experimental and calculated spectra are presented. The mass spectra of ionic products formed after X-ray absorption at various excitation energies are also reported. Specific dissociations were observed for the 1s → π* transition of phenyl ether. In comparison with phenol and phenyl ether, the dependence of the fragmentation on the excitation site and destination state was weak in 1,3-diphenoxybenzene, likely as a result of delocalization of the valence electrons and rapid randomization of energy.

Highly Selective Dissociation of a Peptide Bond Following Excitation of Core Electrons

“…The coreexcitation TDDFT calculation was performed with the LB94 30 functional within the subspace of single excitations from the core (1s) orbitals with the Tamm−Dancoff approximation 31 without relativistic corrections. 29 This method has been shown to work satisfactorily for X-ray absorption spectra in our previous work 32 and by Stener and co-workers. 30,33 The standard Pople type basis set 6-31+G(d,p) was used to calculate the NEXAFS spectra.…”

“…The core-excitation TDDFT calculation was performed with the LB94 functional within the subspace of single excitations from the core (1s) orbitals with the Tamm–Dancoff approximation without relativistic corrections . This method has been shown to work satisfactorily for X-ray absorption spectra in our previous work and by Stener and co-workers. , The standard Pople type basis set 6-31+G­(d,p) was used to calculate the NEXAFS spectra. The basis set was selected on the basis of our experience that the LB94/6-31+G­(d,p) calculation generally reproduces the experimental NEXAFS spectra satisfactorily without the need of significant energy shifts.…”

NEXAFS spectroscopy and site-specific fragmentation of N-methylformamide, N,N-dimethylformamide, and N,N-dimethylacetamide

“…If the anti-bonding orbital is localized one could further expect to preferentially break this bond. 3,4 Many experimental studies have been devoted to the investigation of siteselective bond breaking induced by core excitation both in the gas-phase [5][6][7][8][9][10][11][12][13][14][15] and on solid surfaces, 4,[16][17][18] and it has been demonstrated in both cases. Due to the high cross-section 4 and the potential anti-bonding character of the populated orbital, resonant excitation is expected to be more promising for selective fragmentation compared with core-ionization, a) Electronic mail: vitali.zhaunerchyk@physics.gu.se although selectivity has also been observed in the latter case.…”