S2p core level spectroscopy of short chain oligothiophenes

Abstract

The Near-Edge X-ray-Absorption Fine-Structure (NEXAFS) and X-ray Photoemission Spectroscopy (XPS) of short-chain oligothiophenes (thiophene, 2,2'-bithiophene, and 2,2':5',2″-terthiophene) in the gas phase have been measured in the sulfur L-edge region. The assignment of the spectral features is based on the relativistic two-component zeroth-order regular approximation time dependent density functional theory approach. The calculations allow us to estimate both the contribution of the spin-orbit splitting and of the molecular-field splitting to the sulfur binding energies and give results in good agreement with the experimental measurements. The deconvolution of the calculated S2p NEXAFS spectra into the two manifolds of excited states converging to the L and L edges facilitates the attribution of the spectral structures. The main S2p NEXAFS features are preserved along the series both as concerns the energy positions and the nature of the transitions. This behaviour suggests that the electronic and geometrical environment of the sulfur atom in the three oligomers is relatively unaffected by the increasing chain length. This trend is also observed in the XPS spectra. The relatively simple structure of S2p NEXAFS spectra along the series reflects the localized nature of the virtual states involved in the core excitation process.

Spinterface Formation at α-Sexithiophene/Ferromagnetic Conducting Oxide

“…After a Shirley background subtraction, spectra were decomposed into three multiple doublet components with a 1.2 eV spin–orbit splitting reflecting the nonequivalent S atom in the molecule . Considering that 6T adsorbs on LSMO with its long axis upright to the surface, three such S components can be assigned to the central thiol sulfur atoms from the main chain and the two sulfur atoms at the sides, the one close to the surface and the one that is free. − The lower binding energy peak at 162.7 eV (S1) is typical of sulfide which is presumably S linked to the metal atoms of LSMO surface. , This feature is also consistent with partial charge transfer, as observed for aluminum deposition on 6T . Higher binding-energy components (S2 and S3) can be attributed to the thiophene groups not directly interacting with the substrate because their photoemission-induced core holes are not well screened by valence electrons of the substrate .…”

Theoretical X‐ray spectroscopy of transition metal compounds

“…LR-TDDFT has been successfully applied to main group element K-edges 10,112,116,238 demonstrating good accuracy and predictive power. Attempts have also been made to calculate L-edges of TMs.…”

“…The justification behind is that for high-Z elements, SOC becomes comparable to the largest two-electron integrals and hence significantly influences the one-particle MO basis. Examples of two-component calculations include (a) ZORA DFT-CI-based calculations of oxides, 134 (b) ZORA LR-TDDFT calculations of K-and L-edges of Ti complexes, 271,272 of chemical shifts in K α1,2 emission lines of YbF n 273 and Nb oxide, 274 XAS of gas phase TM oxochlorides, 275 short-chain oligothiophenes XAS and XPS , 236 (iii) real-time DFT calculations of XAS for TM chlorides and oxochlorides, 204 (iv) RASSCF IOTC calculations of XPS of noble gases. 276 For compounds containing low and medium Z elements, the most pragmatic approach is to neglect the spin-dependent part of the Hamiltonian in the two-component scheme, resulting in a one-component approach.…”

Equation-of-Motion Coupled-Cluster Theory to Model L-Edge X-ray Absorption and Photoelectron Spectra

“… a Theory: fc-CVS-EOMIP-CCSD/uC-6-311+G­(3df). Experimental values are from ref (H 2 S, OCS, SO 2 , CS 2 ) and ref (C 4 H 4 S 2 ). …”

“…The theoretical spectra were obtained using a Gaussian convolution function (σ = 0.15 eV) and an energy shift (Δ x ) for a better fit with experiment. The experimental spectra were digitized from ref for SiH 4 , ref for Ar, ref for SO 2 , and ref for thiophene. The vertical dotted lines correspond to the L 2 and L 3 ionization energies.…”