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981.
At the ISOLDE on-line isotope separation facility, the resonance ionisation laser ion source (RILIS) can be used to ionise
reaction products as they effuse from the target. The RILIS process of laser step-wise resonance ionisation of atoms in a
hot metal cavity provides a highly element selective stage in the preparation of the radioactive ion beam. As a result, the
ISOLDE mass separators can provide beams of a chosen isotope with greatly reduced isobaric contamination. With the addition
of a new three-step ionisation scheme for gold, the RILIS is now capable of ionising 26 of the elements. The optimal scheme
was determined during an extensive study of the atomic energy levels and auto-ionising states of gold, carried out by means
of in-source resonance ionisation spectroscopy. Details of the ionisation scheme and a summary of the spectroscopy study are
presented. 相似文献
982.
Y. Akiyama P. von Brentano A. Gelberg 《Zeitschrift für Physik A Hadrons and Nuclei》1987,326(4):517-521
Energies of collective levels in178Hf and234U are compared with predictions of theSU (3) limit of thesdg Interacting Boson Model. All known positive parity states of178Hf below 1.8 MeV (with the exception of a 0+ band) have been satisfactorily reproduced. Most of the bands in234U are also described by the model. However, a few predicted states have no experimental counterpart. The introduction of theg-bosons strongly reduces the previously observed discrepancies between experimentalB(E2)'s in238U and thesd-IBM calculation. 相似文献
983.
984.
I. Kandarakis D. Cavouras P. Prassopoulos E. Kanellopoulos C.D. Nomicos G.S. Panayiotakis 《Applied Physics A: Materials Science & Processing》1998,66(5):521-525
2 SiO4:Mn phosphor was evaluated for use in radiation detectors of medical imaging systems. Zn2SiO4:Mn was used in the form of laboratory-prepared fluorescent layers (screens) with coating weights from 18 to 150 mg/cm2. The phosphor was excited to luminescence by low-energy X-raysusing X-raytube voltages ranging from 15 to 50 kVp. The number
of emitted optical photons per incident X-rayquantum was thus determined for various X-rayenergies and phosphor coating weights.
The optical emission spectrum was also measured and it was used to evaluate the spectral compatibility of Zn2SiO4:Mn with radiographic films, photocathodes and the Si photodiode. Finally, phosphor optical properties were estimated by fitting
a theoretical model to experimental data. Results showed that Zn2SiO4:Mn is more efficient for low-energy X-rays. Its intrinsic conversion efficiency was found equal to 0.08, which is comparable
to that of actually used phosphors. Zn2SiO4:Mn was also adequately compatible with orthochromatic films and the ES-20 photocathode, thus being appropriate for low-voltage
radiography and fluoroscopy.
Received: 31 July 1998/Accepted: 3 August 1998 相似文献
985.
I. N. Koprinarov U. Müller-Jahreis P. Thiele 《Applied Physics A: Materials Science & Processing》1996,62(6):565-570
The crystalline-amorphous transition in GaAs induced by Ar ions (energy 1–3 keV) has been investigated using single-wavelength ellipsometry. The experiments have been performed in-situ at room temperature. Ion damage straggling, amorphization threshold and critical energy density have been derived by means of a simple analytical model for the growth of the amorphous layer. This model is discussed and the corresponding calculations are found to be in satisfactory agreement with experimental data. 相似文献
986.
D. Abbaneo P. Antilogus T. Behnke S.C. Blyth M. Elsing R. Faccini R.W.L. Jones K. Mönig S. Petzold R. Tenchini 《The European Physical Journal C - Particles and Fields》1998,4(2):185-191
Measurements of the forward-backward production asymmetry of heavy quarks in Z decays provide a precise determination of
. The asymmetries are sensitive to QCD effects, in particular hard gluon radiation. In this paper QCD corrections for and are discussed. The interplay between the experimental techniques used to measure the asymmetries and the QCD effects is
investigated using simulated events. A procedure to estimate the correction needed for experimental measurements is proposed,
and some specific examples are given.
Received: 26 February 1998 / Published online: 2 June 1998 相似文献
987.
We investigate the role of the torsion field at the quantum level. One-loop counterterms are calculated in the theory with terms quadratic in the torsion field. We have shown that the theory is finite at the one-loop level. 相似文献
988.
This paper presents the results of plasma temperature and pressure calculations in the parallel plate accelerator during the accelerating process. The plasma pressure is calculated by means in Dalton's law. 相似文献
989.
990.