Vibrational branching ratios in the photoelectron spectra of N2 and CO: interference and diffraction effects

We present a detailed account of existing theoretical methods specially designed to provide vibrationally resolved photoionization cross sections of simple molecules within the Born-Oppenheimer approximation, with emphasis on newly developed methods based on density functional theory. The performance of these methods is shown for the case of N 2 and CO photoionization. Particular attention is paid to the region of high photon energies, where the electron wavelength is comparable to the bond length and, therefore, two-center interferences and diffraction are expected to occur. As shown in a recent work [Canton et al., Proc. Natl. Acad. Sci. U. S. A., 2011, 108, 7302-7306], the main experimental difficulty, which is to extract the relatively small diffraction features from the rapidly decreasing cross section, can be easily overcome by determining ratios of vibrationally resolved photoelectron spectra and existing theoretical calculations. From these ratios, one can thus get direct information about the molecular geometry. In this work, results obtained in a wide range of photon energies and for many different molecular orbitals of N 2 and CO are discussed and compared with the available experimental measurements. From this comparison, limitations and further possible improvements of the existing theoretical methods are discussed. The new results presented in the manuscript confirm that the conclusions reported in the above reference are of general validityWe thank Mare Nostrum BSC, Cineca and CCC-UAM for allocation of computer time. Work supported by the MICINN project Nos. FIS2010-15127, ACI2008-0777 and CSD 200700010 (Spain), the ERA-Chemistry project PIM2010EEC00751, the European COST Action CM0702, the Marie Curie ITN CORINF (EU), and the XCHEM Advanced Grant 290853 of the European Research Counci

Vibrationally-resolved photoelectron angular distributions from randomly-oriented and fixed-in- space N2 and CO molecules

This is an author-created, un-copyedited version of an article published in Journal of physics B: atomic molecular and optical physics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at http://dx.doi.org/10.1088/0953-4075/45/19/194008Vibrationally resolved photoelectron angular distributions from randomly oriented and fixed-in-space N 2 and CO molecules have been evaluated by using an extension of the static-exchange density functional theory that includes the nuclear motion. Both K-shell and valence-shell photoionization have been considered. Comparison with the experimental data, only available for randomly oriented molecules, is very good. Our predictions for molecular-frame photoelectron angular distributions of N 2 show the signature of electron confinement and coherent two-centre interferences as those previously found in H 2. For CO, they exhibit diffraction patterns associated with the scattering of the ejected electron by the neighbouring atomic centre. The conclusions reported in this work suggest that vibrationally resolved photoelectron angular distributions can be a useful instrument to determine structure parameters in these simple moleculesWe thank Mare Nostrum BSC, Cineca and CCC-UAM for allocation of computer time. Work supported by the MICINN project Nos. FIS2010-15127, ACI2008-0777 and CSD 2007-00010 (Spain), the ERA-Chemistry project PIM2010EEC-00751, the European COST Action CM0702, the Marie Curie ITN CORINF, and the XCHEM Advanced Grant 290853 of the European Research Counci

Two- and three-pion quantum statistics correlations in Pb-Pb collisions at 1asNN = 2.76 TeV at the CERN Large Hadron Collider

Correlations induced by quantum statistics are sensitive to the spatiotemporal extent as well as dynamics of particle-emitting sources in heavy-ion collisions. In addition, such correlations can be used to search for the presence of a coherent component of pion production. Two- and three-pion correlations of same and mixed charge are measured at low relative momentum to estimate the coherent fraction of charged pions in Pb-Pb collisions at 1asNN = 2.76 TeV at the CERN Large Hadron Collider with ALICE. The genuine three-pion quantum statistics correlation is found to be suppressed relative to the two-pion correlation based on the assumption of fully chaotic pion emission. The suppression is observed to decrease with triplet momentum. The observed suppression at low triplet momentum may correspond to a coherent fraction in charged-pion emission of 23% \ub1 8%