We report here the recent upgrade of the SAPHIRS permanent photoionization end-station at the DESIRS vacuum ultraviolet beamline of synchrotron SOLEIL, whose performances have been enhanced by installing an additional double-skimmer differential chamber. The smaller molecular beam profile obtained at the interaction region has increased the mass resolution of the double imaging photoelectron photoion coincidence (i(2)PEPICO) spectrometer, DELICIOUS III, installed in the photoionization chamber of the SAPHIRS endstation, by a factor of two, to M/ΔM ∼ 1700 (FWHM). The electron kinetic energy resolution offered by the velocity map imaging (VMI) part of the spectrometer has been improved down to 2.8% (ΔE/E) as we show on the N2 photoionization case in the double skimmer configuration. As a representative example of the overall state-of-the-art i(2)PEPICO performances, experimental results of the dissociation of state-selected O2(+)(B(2)∑(g)(-), v(+) = 0-6) molecular ions performed at the fixed photon energy of hν = 21.1 eV are presented.

Vacuum upgrade and enhanced performances of the double imaging electron/ion coincidence end-station at the vacuum ultraviolet beamline DESIRS

A novel threshold photoelectron-photoion coincidence (TPEPICO) imaging spectrometer at the U14-A beamline of the Hefei National Synchrotron Radiation Laboratory is presented. A set of open electron and ion lenses are utilized to map velocity imaging of photoelectrons and photoions simultaneously, in which a repelling electric field using an extra lens is applied to magnify images of photoelectrons instead of traditional accelerating electric field in order to suppress the contribution of energetic electrons in the threshold photoelectron spectroscopy (TPES) and the mass-selected TPEPICO spectroscopy. The typical energy resolution of TPES is measured to be 9 meV (full width at half maximum), as shown on the P21/2 ionization of argon. The measured mass resolving power for the present TPEPICO imaging spectrometer is above 900 of M/ΔM. Subsequently as a benchmark, oxygen molecule is photoionized by monochromatic synchrotron radiation at 20.298 eV and dissociates to an oxygen atomic ion and a neutral oxygen at...

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A threshold photoelectron-photoion coincidence spectrometer with double velocity imaging using synchrotron radiation

A new ab initio two-dimensional potential energy surface for the Ne–CO interaction is described. The surface was obtained by the supermolecule method at the CCSD(T) level of theory. It is compared with several experimental data sets and with the symmetry-adapted perturbation theory (SAPT) surface of Moszynski et al. [J. Phys. Chem. A 101, 4690 (1997)]. The new surface gives modestly better predictions of experimental results that depend on close approach of Ne to CO, but does not describe the ground state geometry as well as the SAPT surface.

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An ab initio Potential Energy Surface for the Ne-CO

Comprehensive study of the low-temperature oxidation chemistry by synchrotron photoionization mass spectrometry and gas chromatography

At the National Synchrotron Radiation Laboratory, The University of Science and Technology of China, an atomic and molecular physics beamline with an energy range of 7.5-124 eV has been constructed for studying the spectroscopy and dynamics of atoms, molecules and clusters. The undulator-based beamline, with a high-resolution spherical-grating monochromator (SGM), is connected to the atomic and molecular physics end-station. This end-station includes a main experimental chamber for photoionization studies and an additional multi-stage photoionization chamber for photoabsorption spectroscopy. A mid-photon flux of 5 x 10(12) photons s(-1) and a high resolving power is provided by this SGM beamline in the energy range 7.5-124 eV. The size of the synchrotron radiation beam spot at the sample is about 0.5 mm in the vertical direction and 1.0 mm in the horizontal direction. Some experimental results of photoionization efficiency spectroscopy and photoabsorption spectroscopy of atoms and molecules are also reported.

Performance of the atomic and molecular physics beamline at the National Synchrotron Radiation Laboratory.

Experimental and theoretical study of Ne·CO cluster

VUV dissociative photoionization of CHF2Cl

RgNO (Rg=He, Ne, Ar and Kr) complexes were studied using ab initio calculations. The neutral RgNO complex geometry and vibrational frequencies were calculated with the cc-pVDZ basis set at the CCSD(T) level of theory. The calculations show that the geometry of the RgNO complexes is a skewed T-shape with the Rg atom on the oxygen side of the NO molecule, and that the RgNO bond angle increases with mass. The dissociation energies (DE) and ionization energies (IE) of the neutral RgNO complexes, and the dissociation energies of RgNO+ ionic complexes were calculated using Gaussian-2 (G2) methods and a high accuracy energy model. The ionization energies of the neutral RgNO complexes range from 9.265 eV for HeNO to 9.132 eV for KrNO and the dissociation energies of RgNO+ range from 0.017 eV for HeNO+ to 0.156 eV for KrNO+, in line with the expectation based on the increasing polarizability of the Rg atom.

Liqing Hao

Papers

Performance of the atomic and molecular physics beamline at the National Synchrotron Radiation Laboratory.

Experimental and theoretical study of Ne·CO cluster

VUV dissociative photoionization of CHF2Cl

Theoretical Study of Rg·NO (Rg=He, Ne, Ar and Kr) Complexes

The study of photoionization and fragmentation of CHF2Cl : experiment and quantum chemical calculation