We present two different theoretical approaches used to predict the photoelectron and the photoabsorption and discuss their accuracy by comparison with new experimental data. The first method has been developed specifically for molecular inner shell excitation and ionization by Nobuhiro Kosugi since 1980 and implemented in the GSCF3 code. [1] Here the core ionized states and core-to-excited states transitions are solved within the Hartree-Fock approximation by explicitly taking into account the core hole. The excited orbitals to be singly occupied by the core-electron excitations are optimized within the STatic EXchange (STEX) method by freezing the core and the occupied valence HF orbitals of the corresponding core hole state. The calculations have been run for several molecules of biological interest (tyramine, tryptamine, tryptophol, barbituric and thiobarbituric acid) and the obtained XPS and NEXAFS spectra have been compared with the experimental results. [2] The second approach has been developed by Angela Acocella in order to investigate the onset of the ionization dynamics in photoelectron spectroscopy with a quantum-mechanical time-dependent propagator used to evolve the electronic wavefunction [3] with the aim to correlate it to the spectral analysis. In practice, the high energy of the incoming photon triggers a complicated re-organization of the wavefunction where the usually dominant one-photon contribution is combined with all the possible many-photon contributions of the same energy, together with the continuum states of the ionized electron. The presented model proved to reproduce with reasonable accuracy both XPS and UPS spectra of the coronene molecule. [4] [1] N. Kosugi and H. Kuroda, Chem. Phys. Lett. 74 (1980) 490. N. Kosugi and H. Kuroda, Chem. Phys. Lett., 94 (1983) 377. N. Kosugi, Theor. Chim. Acta, 72 (1987) 149. [2] M. Coreno, V. Feyer, O. Plekan, K. C. Prince, R. Richter; W. Caminati, L. Evangelisti, B. M. Giuliano, A. Maris, S. Melandri, manuscript in preparation. [3] A. Acocella, G. A. Jones and F. Zerbetto, J. Phys. Chem. A 110 (2006) 5164-5172. A. Acocella, F. Carbone and F. Zerbetto, J. Am. Chem. Soc., 132 (2010) 12166-12167. [4] A. Acocella, M. De Simone, F. Evangelista, M. Coreno and F. Zerbetto, paper submitted.
Prediction of soft X-ray photo-electron/absorption spectra by ab initio calculations / A. Maris ; A. Acocella. - ELETTRONICO. - (2011), pp. 5-5. (Intervento presentato al convegno New frontiers in Atomic, Molecular and Cluster Physics and Chemistry tenutosi a ICTP, Adriatico Guesthouse Trieste, Italy nel 14–15 November 2011).
Prediction of soft X-ray photo-electron/absorption spectra by ab initio calculations
MARIS, ASSIMO;ACOCELLA, ANGELA
2011
Abstract
We present two different theoretical approaches used to predict the photoelectron and the photoabsorption and discuss their accuracy by comparison with new experimental data. The first method has been developed specifically for molecular inner shell excitation and ionization by Nobuhiro Kosugi since 1980 and implemented in the GSCF3 code. [1] Here the core ionized states and core-to-excited states transitions are solved within the Hartree-Fock approximation by explicitly taking into account the core hole. The excited orbitals to be singly occupied by the core-electron excitations are optimized within the STatic EXchange (STEX) method by freezing the core and the occupied valence HF orbitals of the corresponding core hole state. The calculations have been run for several molecules of biological interest (tyramine, tryptamine, tryptophol, barbituric and thiobarbituric acid) and the obtained XPS and NEXAFS spectra have been compared with the experimental results. [2] The second approach has been developed by Angela Acocella in order to investigate the onset of the ionization dynamics in photoelectron spectroscopy with a quantum-mechanical time-dependent propagator used to evolve the electronic wavefunction [3] with the aim to correlate it to the spectral analysis. In practice, the high energy of the incoming photon triggers a complicated re-organization of the wavefunction where the usually dominant one-photon contribution is combined with all the possible many-photon contributions of the same energy, together with the continuum states of the ionized electron. The presented model proved to reproduce with reasonable accuracy both XPS and UPS spectra of the coronene molecule. [4] [1] N. Kosugi and H. Kuroda, Chem. Phys. Lett. 74 (1980) 490. N. Kosugi and H. Kuroda, Chem. Phys. Lett., 94 (1983) 377. N. Kosugi, Theor. Chim. Acta, 72 (1987) 149. [2] M. Coreno, V. Feyer, O. Plekan, K. C. Prince, R. Richter; W. Caminati, L. Evangelisti, B. M. Giuliano, A. Maris, S. Melandri, manuscript in preparation. [3] A. Acocella, G. A. Jones and F. Zerbetto, J. Phys. Chem. A 110 (2006) 5164-5172. A. Acocella, F. Carbone and F. Zerbetto, J. Am. Chem. Soc., 132 (2010) 12166-12167. [4] A. Acocella, M. De Simone, F. Evangelista, M. Coreno and F. Zerbetto, paper submitted.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
