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Balest R Cho K Daoudi M Ford WT Johnson DR Lingel K Lohner M Rankin P Smith JG Alexander JP Bebek C Berkelman K Bloom K Browder TE Cassel DG Cho HA Coffman DM Drell PS Ehrlich R Gaiderev P Garcia-Sciveres M Geiser B Gittelman B Gray SW Hartill DL Heltsley BK Jones CD Jones SL Kandaswamy J Katayama N Kim PC Kreinick DL Ludwig GS Masui J Mevissen J Mistry NB Ng CR Nordberg E Patterson JR Peterson D Riley D Salman S Sapper M Würthwein F Avery P Freyberger A Rodriguez J Stephens R Yang S Yelton J 《Physical review letters》1994,72(15):2328-2331
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A system of computer programs has been developed to predict and interpret the infrared spectra of molecules, ions, radicals and of chemically interacting species. The frequency parameters (or force constants) and the intensity parameters (or atomic polar tensors (APTs)) are calculated using the Gaussian-76 program for quantum mechanical calculations with a 4–31G basis set. The resultant wavenumbers and intensities have been used to predict the fundamental infrared spectra of water molecules interacting with different molecular species. The corresponding wavenumber shifts and intensity changes from the spectrum of the non-interacting water molecule are dependent upon both the geometrical orientation and the electron-donating properties of the interacting species. The intensity parameters can be further analyzed by using the charge-charge flux-overlap (CCFO) interpretation of the APTs. This interpretation is helpful in pinpointing the exact source of the perturbation that produces the intensity change. The significance is discussed of each of these CCFO terms in predicting the infrared intensities of molecules undergoing intermolecular interaction. 相似文献
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The energy deposited by many types of radiation, including the high energy heavy ions found in galactic cosmic rays, is more damaging to biological systems than equal amounts of energy delivered by conventional X-ray irradiation. Average quantities such as dose and LET do not provide the information necessary to predict the effect of these types of irradiation at low doses. Charged particle fluence, as a function of the particle charge and velocity, is the ideal way to characterize the radiation, but in many practical situations the fluence spectrum is not known, and cannot be easily obtained. Low pressure proportional counters, simulating tissue volumes a few micrometers in diameter, provide a convenient alternative to dose and fluence measurements. Such instruments are used routinely on the space shuttle and space station to evaluate radiation exposures. However, the energy deposited does not relate directly to energy transferred because a significant amount of energy is carried away from the particle track by delta rays. Using experimental data and simple approximations we show that energy deposited in targets 0.02, 2, and in diameter differs by easily measurable amounts. These results suggest that it is possible to estimate the fraction of the events that are due only to delta rays, and, thus, the average velocity of the particles that deposited the energy, from measurements of energy imparted in different size sites. 相似文献
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Four-point impedance spectroscopy of solid materials systems is severely hampered by unavoidable voltage-divider effects associated with the reference electrodes. As demonstrated by test circuit studies and experiments with Pt/YSZ/Pt cells (with embedded silver reference electrodes), high impedance reference electrodes can produce distorted and erroneous impedance data. The relationships between these data and the sample properties (conductivity, dielectric constant) and instrument limitations (input impedance/capacitance) are derived. Successful four-point impedance measurements on conductive systems require large effective dielectric constants, which may be unattainable in bulk solids, but are often associated with internal interfaces. 相似文献