Experimental and theoretical investigation of the Auger electron spectra of isothiocyanic acid, HNCS.

We investigate isothiocyanic acid, HNCS, by resonant and nonresonant Auger electron spectroscopy at the K-edge of carbon and nitrogen, and the L-edge of sulfur, employing soft X-ray synchrotron radiation. The C1s and N1s ionization energies as well as the S2s and S2p ionization energies are determined and X-ray absorption spectra reveal the transitions from the core to the virtual orbitals. Final states for all normal Auger electron spectra and the resonant ones recorded at the carbon and nitrogen edge are assigned and rationalized with theoretical spectra obtained with a wave-function based protocol.

X-ray photoelectron and NEXAFS spectroscopy of thionated uracils in the gas phase.

We present a comprehensive, combined experimental and theoretical study of the core-level photoelectron and near-edge x-ray absorption fine structure (NEXAFS) spectra of 2-thiouracil, 4-thiouracil, and 2,4-dithiouracil at the oxygen 1s, nitrogen 1s, carbon 1s, and the sulfur 2s and 2p edges. X-ray photoelectron spectra were calculated using equation-of-motion coupled-cluster theory (EOM-CCSD), and NEXAFS spectra were calculated using algebraic diagrammatic construction and EOM-CCSD. For the main peaks at O and N 1s as well as the S 2s edge, we find a single photoline.

Resonant Auger decay of iodobenzene below the I 4d edge.

New data are presented on the resonant Auger decay of iodobenzene (C6H5I) in the region of the I 4d-1 ionization threshold. The excited molecules decay by participator and spectator processes to populate single-hole valence states and two-hole, one-particle excited states of the cation, providing new information on the structure of C6H5I+. Excitation of dissociative C6H5I (I 4d5/2,3/2-1)σ* resonances can, in principle, result in ultrafast dissociation to C6H5 + I** and the subsequent autoionization of I**, but no evidence for this process is observed.

Resonant Auger decay of dissociating CH3I near the I 4d threshold.

Resonant Auger processes provide a unique perspective on electronic interactions and excited vibrational and electronic states of molecular ions. Here, new data are presented on the resonant Auger decay of excited CH3I in the region just below the I 4d-1 ionization threshold. The resonances include the Rydberg series converging to the five spin-orbit and ligand-field split CH3I (I 4d-1) thresholds, as well as resonances corresponding to excitation from the I 4d5/2,3/2 orbitals into the σ* lowest unoccupied molecular orbital.

Alternative Pathway to Double-Core-Hole States.

Excited double-core-hole states of isolated water molecules resulting from the sequential absorption of two x-ray photons have been investigated. These states are formed through an alternative pathway, where the initial step of core ionization is accompanied by the shake-up of a valence electron, leading to the same final states as in the core-ionization followed by core-excitation pathway. The capability of the x-ray free-electron laser to deliver very intense, very short, and tunable light pulses is fully exploited to identify the two different pathways.