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Papers by michele alagia

The Journal of Chemical Physics, 2016

Near-edge X-ray absorption fine-structure (NEXAFS) spectra measured at the C, N, and O Kedges for... more Near-edge X-ray absorption fine-structure (NEXAFS) spectra measured at the C, N, and O Kedges for three molecules containing the amide moiety, N-methylformamide (HCONHCH 3), N,Ndimethylformamide (HCON(CH 3) 2), and N,N-dimethylacetamide (CH 3 CON(CH 3) 2) are presented. These molecules have similar structures and differ by the number of methyl groups located at the molecular ends. The fragmentation of these molecules after resonant excitation at different K-edge resonances is also investigated, using a 3D-ion imaging time-of-flight spectrometer. A comparison between the molecules with respect to the relative contributions of the fragments created upon excitation at distinct resonances reveals site-specific fragmentation. Further information about the character of the core-excitation and dissociation process is obtained from the angular distributions of the ion fragments.

The journal of physical chemistry. A, Jan 14, 2016

In this work, hydrogen peroxide has been studied with threshold photoelectron (TPE) spectroscopy ... more In this work, hydrogen peroxide has been studied with threshold photoelectron (TPE) spectroscopy and photoelectron (PE) spectroscopy. The TPE spectrum has been recorded in the 10.0-21.0 eV ionization energy region, and the PE spectrum has been recorded at 21.22 eV photon energy. Five bands have been observed which have been assigned on the basis of UCCSD(T)-F12/VQZ-F12 and IP-EOM CCSD calculations. Vibrational structure has only been resolved in the TPE spectrum of the first band, associated with the X̃(2)Bg H2O2(+) ← X̃(1)A H2O2 ionization, on its low energy side. This structure is assigned with the help of harmonic Franck-Condon factor calculations that use the UCCSD(T)-F12a/VQZ-F12 computed adiabatic ionization energy (AIE), and UCCSD(T)-F12a/VQZ-F12 computed equilibrium geometric parameters and harmonic vibrational frequencies for the H2O2 X̃(1)A state and the H2O2(+) X̃(2)Bg state. These calculations show that the main vibrational structure on the leading edge of the first TPE ...

Physical Review Letters, 2006

An influence of static magnetic fields on the fluorescence yield spectrum of He in the vicinity o... more An influence of static magnetic fields on the fluorescence yield spectrum of He in the vicinity of the N 2 thresholds has been observed. The experimental results are in excellent agreement with predictions based on multichannel quantum defect theory, and it is demonstrated that the Rydberg electron ' mixing due to the diamagnetic interaction is essential for the description of the observed fluorescence yield intensity enhancement.

Cl ) H 2 ) HCl ) H reactions at 5.85 kcal mol~1 and 6.3 and 6.4 kcal mol~1 collision energies, re... more Cl ) H 2 ) HCl ) H reactions at 5.85 kcal mol~1 and 6.3 and 6.4 kcal mol~1 collision energies, respectively, ) D 2 ) DCl ) D obtained from high-resolution crossed molecular beam experiments. In addition, quasiclassical trajectory (QCT) and quantum mechanical (QM) dynamical calculations have been carried out for these reactions on the G3 potential energy surface (T. C. Allison et al., J. Phys. Chem., 1996, 100, 13575). Reaction probabilities, integral and diÜerential cross sections have been calculated using the QCT and QM methodologies, and a comparison of these results is presented. The molecular beam results have been simulated using the theoretical calculations, and theory and experiment are in reasonably good agreement.

The Journal of Physical Chemistry A, 2001

Near edge X-ray absorption fine structure (NEXAFS) spectra of 2-mercaptobenzothiazole have been i... more Near edge X-ray absorption fine structure (NEXAFS) spectra of 2-mercaptobenzothiazole have been investigated from experimental and theoretical points of view. High-resolution NEXAFS spectra (total-ion-yield) have been obtained in the gas phase near the carbon and nitrogen K-edges, and sulfur L 2,3-edges using synchrotron radiation. The experimental data are interpreted with the help of static-exchange (STEX) ab initio calculations for the different edges and compared with previously reported experimental and theoretical spectra of a similar molecule, the 2-mercaptobenzoxazole. The good agreement between experiment and theory allows for a detailed discussion and assignment of the various features observed. A vibrational progression at the C K-edge is also identified in the highly resolved experimental spectrum.

Surface Review and Letters, 2002

We report the Near Edge X-ray Absorption Fine Structure Spectra (NEXAFS) of a series of oxygen-co... more We report the Near Edge X-ray Absorption Fine Structure Spectra (NEXAFS) of a series of oxygen-containing organic molecules, namely formaldehyde, acetaldehyde, acetone, formic acid, methanol and dimethyl ether (DME), measured with high resolution at the carbon and oxygen edges. A vibrational progression has been observed at the oxygen 1s → π* resonance of formaldehyde, indicating that this state is bound with an excited state C=O stretching frequency of 136 meV. The spectra are compared with previous measurements and the applicability of the chromophore concept is tested for the functional groups present in these molecules.

Physical Review A, 2004

We report a joint experimental and theoretical study of circular dichroism in the valence photoel... more We report a joint experimental and theoretical study of circular dichroism in the valence photoelectron spectra of a free chiral molecule. The circular dichroism in photoelectron spectroscopy is measured at the magic angle for various valence states of R͑+͒ and S͑−͒ methyl-oxirane enantiomers in the vapor phase. The maximum dichroism measured is about 5 ϫ 10 −2. Experimental and theoretical results are in agreement. The ab initio calculation employs a multicentric basis set of B-spline functions and a Kohn-Sham Hamiltonian.

Physical Review A, 2011

Laser orientation in the initial state has been used to study the properties of satellite transit... more Laser orientation in the initial state has been used to study the properties of satellite transitions in inner-shell photoionization of rubidium atoms. The linear magnetic dichroism in the angular distribution (LMDAD) has been utilized to probe the continuum waves of orbital angular momentum conserving monopole, and angular momentum changing conjugate satellites, accompanying the 4p ionization of atomic Rb. We show experimentally that LMDAD of both types of satellite transitions is nonzero and that LMDAD of monopole satellites, measured as a function of photon energy, mimics the LMDAD of direct photoionization, whereas the LMDAD of conjugate transitions deviates drastically from that trend. The results indicate that conjugate transitions cannot be described theoretically without explicit inclusion of electron-electron interaction. The present data can thus be used as a very precise test of current models for photoionization.

Physical Chemistry Chemical Physics, 2000

for each of the systems as well as some statistics concerning basis set sizes for selected JPS bl... more for each of the systems as well as some statistics concerning basis set sizes for selected JPS blocks for some of the energies studied. Details of the basis set notation are

Journal of Physics B: Atomic, Molecular and Optical Physics, 2010

The photoionization of ground state and 6p laser-excited Cesium atoms was studied above their 4d ... more The photoionization of ground state and 6p laser-excited Cesium atoms was studied above their 4d ionization threshold. The 4d photoelectron spectrum of 6p laser-excited atoms shows a stronger excitation of satellites upon ionization than its ground state counterpart. The relative intensities of satellite and main photolines show a slow variation with the incoming photon energy for both the ground state and the 6p laser-excited states. An assignment of the excited state spectra, supported by recently published ground state photoionization spectra and calculations, is given and a preliminary analysis of the 4d Auger spectrum of laser-excited atoms is also presented.

Journal of Physics: Conference Series, 2008

We present here the results of synchrotron radiation-excited UV-photoemission investigation and D... more We present here the results of synchrotron radiation-excited UV-photoemission investigation and DFT calculations on vinylferrocene (VFC), a redox molecule suitable for applications in molecular electronics. A detailed assignment is discussed of the valence photoelectron spectra (UPS), which provides new data on the electronic structure and offers a partial re-interpretation of previous assignments on VFC based on theoretical and experimental evidences.

The Journal of Physical Chemistry Letters, 2013

We provide experimental evidence for interatomic Coulombic decay (ICD) in mixed rare gas dimers f... more We provide experimental evidence for interatomic Coulombic decay (ICD) in mixed rare gas dimers following resonant Auger decay. A velocity map imaging apparatus together with a cooled supersonic beam containing Ar 2 and NeAr dimers was used to record the energy and angular distributions of electrons in coincidence with two mass selected ions following the excitation of a number of resonances converging to the Ar 2p 3/2 −1 threshold using synchrotron radiation. It is shown that the ICD process can be controlled by the choice of the partner atom in the dimer or of the resonance that triggers the resonant Auger decay.

Journal of Electron Spectroscopy and Related Phenomena, 2004

... Simulations of the observed TPE peak shape have been carried out using the parameters obtaine... more ... Simulations of the observed TPE peak shape have been carried out using the parameters obtained from the analysis of the XETECO spectrum (Fig. 3). These simulations were made using the PCI theory as formulated by van der Straten et al. [21] for ionization near threshold. ...

Journal of Electron Spectroscopy and Related Phenomena, 2001

The K-edge photoionization spectra of metastable O (a D) molecules and O (P) atoms have been inve... more The K-edge photoionization spectra of metastable O (a D) molecules and O (P) atoms have been investigated at high 2 g 1 resolution. Both species were prepared on-line using a microwave discharge. For the molecule the transition to the p* P state has been identified below the ionization threshold, using total-ion-yield spectroscopy. Above the edge the previously 2 1 unobserved D state of the O core-hole ion has been located by photoelectron spectroscopy. The results provide a link 2 between the singlet and triplet manifolds of the core excited states of the oxygen molecule. The 1s excited states of the oxygen atom were also studied. The high resolution allowed the characterization of higher members of the Rydberg series and first linewidth measurements for those transitions.

The Journal of Chemical Physics, 2000

The dynamics of the interactions of atomic chlorine with the surface of a saturated hydrocarbon l... more The dynamics of the interactions of atomic chlorine with the surface of a saturated hydrocarbon liquid, squalane, were investigated and compared to the results of an earlier study on analogous oxygen-atom interactions. Beams of continuous supersonic chlorine atoms were directed onto a squalane surface, and the volatile products, Cl and HCl, were observed by mass spectrometry as a function of

The Journal of Chemical Physics, 1998

ABSTRACT The dynamics of the reactions O(1D)+H2→OH+H and O(1D)+D2→OD+D have been investigated in ... more ABSTRACT The dynamics of the reactions O(1D)+H2→OH+H and O(1D)+D2→OD+D have been investigated in crossed molecular beam experiments with mass spectrometric detection at the collision energies of 1.9 and 3.0 kcal/mol, and 5.3 kcal/mol, respectively. From OH(OD) product laboratory angular and velocity distribution measurements, center-of-mass product translational energy and angular distributions were derived. The angular distributions are nearly backward–forward symmetric with a favored backward peaking which increases with collision energy. About 30% of the total available energy is found to be channeled into product translational energy. The results are compared with quasiclassical trajectory calculations on a DIM (diatomic-in-molecules) potential energy surface. Related experimental and theoretical works are noted. Insertion via the 1 1A′ ground state potential energy surface is the predominant mechanism, but the role of a second competitive abstraction micromechanism which should evolve on one of (or both) the first two excited surfaces 1A″ and 2 1A′ is called into play at all the investigated energies to account for the discrepancy between theoretical predictions and experimental results. © 1998 American Institute of Physics.

The Journal of Chemical Physics, 2002

ABSTRACT

The Journal of Chemical Physics, 2004

The present study describes the characterization of energy and structure of HBr(2+) in its low-ly... more The present study describes the characterization of energy and structure of HBr(2+) in its low-lying electronic states, achieved through an extension of a new empirical method [Chem. Phys. Lett. 379, 139 (2003)] recently introduced to evaluate the interatomic interaction in the HX(2+) (X=F,Cl,Br,I) molecular dications. The method is based on identification of the main components of the interaction and their evaluation through some simple correlation formulas. Potential energy curves, given in a simple, natural, and analytical form, made possible the calculations of some important properties, such as double-photoionization energy thresholds, vibrational spacing, average lifetime, and Franck-Condon factors. The predictions, compared with data available in the literature, are of great interest for the analysis and interpretation of some new experimental results.