1,721,035 research outputs found
RELATIVE ORDERING AND SPACING OF N-LEVEL AND PI-LEVEL IN ISOMERIC BIPYRIMIDINES - A THEORETICAL AND GAS-PHASE UV PHOTO-ELECTRON SPECTROSCOPIC STUDY
No full textGENERAL TRENDS IN THE MOLECULAR PHYSICS OF AZABIPHENYLS - A QUANTUM CHEMICAL AND PHOTOELECTRON SPECTROSCOPIC STUDY
No full textQUANTUM-MECHANICAL AND ULTRAVIOLET PHOTOELECTRON SPECTROSCOPIC STUDIES OF AZABIPHENYLS - THE CASE OF 4-PHENYLPYRIMIDINE
No full textACCEPTOR ABILITY AND DONOR STRENGTH OF BIPHENYL-LIKE ALPHA-DIIMINE LIGANDS - A THEORETICAL AND GAS-PHASE UV PHOTOELECTRON SPECTROSCOPIC STUDY
No full textEffect of the silicon surface step on the acetylene reaction with the Si(111)7x7 reconstructed surface
No full textIn this paper we report on a morphological investigation of the growth mechanism of silicon carbide (SiC) on the Si(111)7 x 7 surface. The role of the substrate morphology and temperature during acetylene exposure has been studied with the aim to obtain high quality SiC films. We compared two starting points of silicon substrate: one characterised by step bunching and one by monoatomic terraces of the same width. Our results indicate that a lower density of defects and holes is present in the former case. (C) 2004 Elsevier B.V. All rights reserved
Vibrationally resolved O is photoelectron spectrum of CO2: vibronic coupling and dynamic core-hole localization
No full textThe C and O 1s photoelectron lines of the CO2- molecule in the gas phase have been measured with vibrational resolution in the threshold region. The vibrational fine structure on the O 1s line is completely dominated by the antisymmetric stretching mode with a frequency of 307 (+/-3) meV. This mode can be excited only via vibronic coupling, as predicted by Domcke and Cederbaum [Chem. Phys. 25, 189 (1977)], and provides a mechanism for dynamic core-hole localization. Relaxation effects are found to affect strongly the vibrational intensity distribution of the photoelectron line
EXPERIMENTAL AND THEORETICAL APPROACH TO THE ELECTRONIC-STRUCTURE AND THE MOLECULAR-CONFORMATION OF AZABIPHENYLS - ASYMMETRIC BIPYRIDINES
No full textLow-temperature adsorption states of benzene on Si(111)7x7 studied by synchrotron-radiation photoemission
No full textThe benzene adsorption on Si(111)7 x 7 was investigated by synchrotron-radiation valence-band photoemission in the temperature range 30-300 K. We found that when benzene is adsorbed on Si(111)7 x 7 at low temperature there is a one-to-one correspondence between the adsorbed and the gas-phase features. Furhermore, the interaction of benzene with the surface states is very weak, hinting at a physisorption process. Upon temperature increase, the adsorption features change gradually, but significantly. In particular, we observe a splitting of the features related to the degenerate orbitals, indicating that the benzene bond to the silicon surfaces is turning into chemisorption. This is the first evidence by photoemission spectroscopy that such a transition occurs, to our knowledge. Furthermore, the spectrum we obtain upon transition from the physisorbed to the chemisorbed state corresponds to the one obtained by dosing benzene at room temperature, thus showing that the chemisorption state does not depend on the way it is achieved. Upon exposure to a benzene multilayer we observe a direct transition from multilayer to chemisorbed state without intermediate transition to a physisorbed state, thus indicating that the multilayer desorption and the physisorption-to-chemisorption transition occur simultaneously. The adsorption of a few benzene overlayers on Si(111)7 x 7 at low temperature allowed us to monitor simultaneously both the first adlayer (hence the physisorption-to-chemisorption transition) and the overlayer features (hence the multilayer desorption), confirming that the physisorption-to-chemisorption transition and multilayer desorption are competing processes, and indicating a way to study substrate-adsorbate systems
Resonant photofragmentation of methanol at the carbon and oxygen K-edge by high-resolution ion-yield spectroscopy
No full textResonant photofragmentation of core-excited methanol has been studied with high-resolution partial ion-yield spectroscopy near both the carbon and oxygen K-edge. Non-coincident and coincident fragmentation channels were monitored simultaneously. A steep increase in the coincidence yield curves above the ionization threshold, where the normal Auger decay produces doubly charged or multiply charged species which yield two or more charged fragments, has been observed. A relevant difference in resonant structure has been observed while comparing the fragmentation at the carbon K-edge and the oxygen K-edge. Evidence for inter-atomic Auger decay is presented for one particular single channel around the oxygen K-edge
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