Multiple photoionization of Xe near the 3d 5/2 -shell threshold photoionization region is studied by threshold electron-ion coincidence spectroscopy. The coincidence spectra of Xe 3+ to Xe 7+ ions exhibit characteristic profiles associated with multi-step post-collision interactions in Auger cascades following 3d 5/2 -shell threshold photoionization. The Auger cascade decay channels leading to the formation of multiply charged ions are deduced from the energies of the profile peaks, which increase gradually with increasing charge state. The formation of Xe 3+ to Xe 5+ ions is found to arise from cascades of normal Auger decays, whereas the formation of Xe 6+ and Xe 7+ ions involves double Auger decays. The branching ratio of double to normal Auger decays is estimated to be 0.25 (±0.1) for the decays following the creation of 3d 5/2 -hole states in Xe.
Use of a beam of biradicaloid such as dialkyl group-III nitrene produced by the method of photodissociation of energetic compound beams (PDECB) is expected to be advantageous to the low-temperature thin-film growth of stoichiometric group-III nitride. Through the clarification of fundamental processes involved in pyrolysis as well as photolysis of dimethylgallium azide [(CH3)2GaN3], dimethylaluminum azide [(CH3)2AlN3], and dimethylboron azide [(CH3)2BN3] based on post-self-consistent field ab initio molecular orbital methods, we discuss the suitability of these possible source compounds for the production of beams of dimethylgalliumnitrene [(CH3)2GaN], dimethylaluminumnitrene [(CH3)2AlN], and dimethylboronnitrene [(CH3)2BN] by the PDECB method. The theoretical results suggested that (CH3)2GaN3 is a promising PDECB source material in that this molecule possesses the nature of unimolecular metastable dye.
Photoelectron-current measurement by low-frequency electromodulation probe (PMMP) is proposed as a sensitive method to determine the rate Gr of neutral free radical production by the photodeionization of negative ion beams (PDINIB). The PMMP method was employed to evaluate the production rate in a trial surface-processing apparatus developed in the author’s laboratory utilizing a steady-flux refined beam of neutral free radicals produced by the PDINIB procedure. A Cu−63 negative ion beam of kinetic energy Ei varied up to 15 keV was irradiated with a 514.5 nm visible light beam from a 25 W cw Ar+ ion laser. The detection limit of the production rate by the measurement setup was 6×109/s under the conditions that Ei=15 keV, the negative ion beam current Ii=4 μA, and the laser power P=6 W. Based on the results of these basic experiments, furthermore, the photodeionization efficiency defined by eGr/Ii where e is the elementary electric charge was estimated to be 27±6% under the conditions that Ei=15 keV, Ii=40 μA, and P=18 W.
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