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P O'Keeffe,
P Bolognesi,
M Coreno,
A Moise,
R Richter,
G Cautero,
L Stebel,
R Sergo, L Pravica,
Y Ovcharenko,
L Avaldi
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ABSTRACT: A velocity map imaging/ion time-of-flight spectrometer designed specifically for pump-probe experiments combining synchrotron and laser radiations is described. The in-house built delay line detector can be used in two modes: the high spatial resolution mode and the coincidence mode. In the high spatial resolution mode a kinetic energy resolution of 6% has been achieved. The coincidence mode can be used to improve signal-to-noise ratio for the pump-probe experiments either by using a gate to count electrons only when the laser is present or by recording coincidences with the ion formed in the ionization process.
The Review of scientific instruments 03/2011; 82(3):033109. · 1.52 Impact Factor
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P. O’Keeffe,
P. Bolognesi,
A. Mihelič,
A. Moise,
R. Richter,
G. Cautero,
L. Stebel,
R. Sergo, L. Pravica,
E. Ovcharenko,
P. Decleva,
L. Avaldi
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ABSTRACT: Photoelectron distributions of the polarized 2p53d Rydberg states of neon have been studied with a newly built velocity map imaging analyzer. The atoms were polarized by absorption of synchrotron radiation and ionized by an infrared laser. The asymmetry parameters β2 and β4 characterizing two-photon resonant ionization have been extracted from the measured images and compared with the results of a quantum defect treatment. To achieve a good theoretical description of the data, it is necessary to take into account the dependence of the dipole transition matrix elements and phases of the partial waves on the angular momentum quantum numbers pertaining to various continuum channels.
Phys. Rev. A. 11/2010; 82(5).
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ABSTRACT: A new photoelectron imaging spectrometer has been used to measure the photoelectron angular distributions in pump-probe experiments where the VUV radiation of the synchrotron is used to prepare an aligned state of the target and the radiation of a Ti:sapphire laser ionizes it. The new set-up and its use to study the photoionization of the He 1s3p (1P1) and Ne 2p5nd (1P1) states are described.
Journal of Physics Conference Series 06/2010; 235(1):012006.
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ABSTRACT: The contribution of the dipole and non-dipole terms to the angular distribution of the photoelectrons from the N K shell of randomly oriented N2 molecules has been measured up to 80 eV above the N 1s threshold. The results are compared with all the previous experimental data and theoretical results. Consistently with the predictions of calculations performed in the frame of density functional theory (Toffoli and Decleva 2006 J. Phys. B: At. Mol. Opt. Phys. 39 2681) and in the random phase approximation (Hosaka et al 2006 J. Phys. B: At. Mol. Opt. Phys. 39 L25) the present data show that the non-dipole effects are rather small in the region investigated.
Journal of Physics B Atomic Molecular and Optical Physics 11/2008; 41(22):221002. · 1.88 Impact Factor
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ABSTRACT: The ionization of Mg 2p by electron impact has been studied at about 400 and 1000 eV incident energy and small momentum transfer via (e,2e) experiments. Two kinematical conditions have been chosen in order to study the coincidence angular distribution in the case where either only the direct 2p ionization contributes or the decay of the 2p core hole plays a role, too. The results have been compared with distorted-wave Born approximation calculations.
Phys. Rev. A. 05/2008; 77(5).
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JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS. 01/2008;
