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The Angle Resolved PhotoEmission Spectroscopy (ARPES) end station (fig. 1) is equipped with a differentially pumped inner vessel housing a time-of-flight (TOF) 3D-ion-momentum imaging mass spectrometer, and a flash pyrolitic radical source mounted on a XYZ translator.The detection axis of the TOF mass spectrometer , the photon and the molecular beam axes are mutually perpendicular.
In fig. 2 , a sketch of the experimental set up is shown. The energy selected synchrotron light beam crosses an effusive molecular beam of N2 and the product ions are then detected in coincidence with photoelectrons. The monochromator uses a 400 l/mm spherical grating in first diffraction order. The entrance and exit slits of the monochromator have been adjusted in order to have a resolution between 2.0 and 1.5 meV in the investigated 28–40 eV photon energy range. The resolution and the energy scale calibration has been checked by measuring some known sharp resonances in the total ion yield of argon in this energy range. To avoid spurious ionization effects, due to photons of higher order energy, a magnesium film filter was used. The N2 molecular beam and the VUV light beam crosses at right angles, with the light polarization vector being parallel to the synchrotron ring plane and perpendicular to the time-of-flight direction of detected ions.

Fig. ARPES apparatus at Gas Phase beam line.

Full-size image (36 K)
Fig. 2. A schematic sketch of the experimental setup.

The ion detection system has been built up according to the model described in M. Lavollée Rev. Sci. Instrum., 70 (1999), p. 2968. Such a position sensitive detector is particularly designed in order to measure the spatial momentum components of the dissociation ionic products. However, for the experiment described here, the dependence has been not used and therefore only total ion arrival times to the micro channel plate detector have been considered. Practically, mass spectra were recorded using photoelectrons as starting pulses, and then ions were counted as a function of the delay times. A computer controlled all the experiment components and also recorded experimental data. The incident photon flux and gas pressure have been monitored and stored in separate acquisition channels. Ion yields have been then corrected for pressure and photon flux changes while varying the photon energy.

Selected publications

  1. Angular and energy distribution of fragment ions in dissociative double photoionization of acetylene molecules at 39 eV 
    Alagia M, Callegari C, Candori P, Falcinelli S, Pirani F, Richter R, Stranges S, Vecchiocattivi F 
    The Journal of Chemical Physics, Vol. 136 - 20, pp. 204302-6 (2012) 
    doi: 10.1063/1.4720350
  2. C--C bond unsaturation degree in monosubstituted ferrocenes for molecular electronics investigated by a combined near-edge x-ray absorption fine structure, x-ray photoemission spectroscopy, and density functional theory approach 
    Boccia A, Lanzilotto V, Marrani AG, Stranges S, Zanoni R, Alagia M, Fronzoni G, Decleva P 
    J CHEM PHYS, Vol. 136 - 13, pp. 134308-11 (2012) 
    doi: 10.1063/1.3698283
  3. Double Photoionization of CO2 Molecules in the 34-50 eV Energy Range 
    Alagia M, Candori P, Falcinelli S, Lavolleé M, Pirani F, Richter R, Stranges S, Vecchiocattivi F 
    J PHYS CHEM A, Vol. 113 - 52 (2009)
  4. Core-shell photoabsorption and photoelectron spectra of gas-phase pentacene: experiment and theory 
    Alagia M., Baldacchini C., Betti M.G., Bussolotti F., Carravetta V., Ekstrom U., Mariani C., Stranges S. 
    J CHEM PHYS, Vol. 122 - 12 (2005)
  5. Low-lying electronic states of HBr2+ 
    Alagia M, Brunetti BG, Candori P, Falcinelli, S, Teixidor MM, Pirani F, Richter R, Stranges S, Vecchiocattivi F 
    J CHEM PHYS, Vol. 120 - 15 (2004)
Last Updated on Tuesday, 13 January 2015 16:31