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111.
S. Roy Morrison 《Surface science》1974,45(1):20-38
Surface states due to Be, Mg, Ca, Sr, and Ba ions deposited on ZnO as salts with varying anions have been examined, to make available a selection of nonvolatile surface states for later study, and to provide a relatively simple group of substitutional surface states that could be used to compare theories with experiment. The results indicate that Be++ and Ba++ additions lead to shallow acceptor levels, near or above the ZnO conduction band, while deeper acceptor levels (as low as 0.9 eV below the conduction band) are associated with Mg++, Ca++, and Sr++ additions. The energy of the resulting surface state depends somewhat on whether the alkaline earth species is added as the hydroxide or the fluoride. There is evidence of a high density donor level at 1.1 eV below the conduction band perhaps associated with surface lattice oxygen or with OH? groups. Arguments arepresented suggesting that the surface state is associated with the alkaline earth ions at lattice sites at the ZnO/additive interface, and some of the factors are discussed that must be considered in a theoretical model. 相似文献
112.
D.E. Wortman R.P. Leavitt C.A. Morrison 《Journal of Physics and Chemistry of Solids》1974,35(4):591-593
An analysis has been made of the optical spectrum of Tm3+ in YVO4 reported by K. D. Knoll. The approach taken was to describe the Tm3+ free ion as completely as possible and then to describe the effects of the crystal field on these levels. Parameters were obtained that gave an r.m.s. deviatioa of 10.6 cm?1 in a least squares fit. In Knolls' earlier analysis, which did not describe the free ion adequately, several sets of parameters were given that are consistent with different portions of the spectrum. The results computed with our parameters gave a new interpretation of the 3F4 and 3H5 multiplets and gave g∥ factors in good agreement with the measurements. The efiects of the hyperfine interaction and the spin-crystal field interaction on the energy levels resulted in displacements of smaller than 0.1 cm?1. 相似文献
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G. Otter H. Remplewski G. Rudolph L. Becker R. Klein W. Lohmann H.J. Schreiber K. Böckmann U. Idschok J. Lowsky B. Schröder D.J. Kocher D.R.O. Morrison K.-L. Wernhard T. Coghen K.W.J. Barnham R. Eason H. Rohringer 《Nuclear Physics B》1979,155(2):295-306
Results are presented for p → (ΛK+) dissociation in the reactions K?p → ΛK+K? and and π±p → ΛK+π±at 10 and 16 GeV/c. The cross sections for the low-mass ΛK+ enhancement are compatible with the energy dependence σ ∝ plab?0.3. The t′ spectra or the (ΛK+) threshold enhancement are exponential in shape. Its decay angular distribution reveals neither s-channel nor t-channel helicity conservation. The relative probabilities of the processes dissociation are in the ratios 100 : 10 : 0.2, independent of the nature of the incident particle. 相似文献
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Abstract— Photolysis of N,N-dimethylthymine (DMT) and urocanic acid (UA) gives rise to two isolable cyclobutane adducts. N,N-dimethylthymine also photosensitizes UA E / Z isomerization. Neither phenomenon is affected by a triplet quencher, and 1 DMT* is proposed as the likely reactive species. If so, prior complexation of DMT and UA would be necessary in order for their interaction to be competitive with DMT radiationless decay. These observations are potentially related to the effect of UA on viral DNA described in the following paper. 相似文献
118.
Robert D.?Carr Harvey J.?GreenbergEmail author William E.?Hart Goran?Konjevod Erik? Lauer Henry?Lin Tod?Morrison Cynthia A.?Phillips 《Mathematical Programming》2006,107(1-2):337-356
We present a series of related robust optimization models for placing sensors in municipal water networks to detect contaminants
that are maliciously or accidentally injected. We formulate sensor placement problems as mixed-integer programs, for which
the objective coefficients are not known with certainty. We consider a restricted absolute robustness criteria that is motivated
by natural restrictions on the uncertain data, and we define three robust optimization models that differ in how the coefficients
in the objective vary. Under one set of assumptions there exists a sensor placement that is optimal for all admissible realizations
of the coefficients. Under other assumptions, we can apply sorting to solve each worst-case realization efficiently, or we
can apply duality to integrate the worst-case outcome and have one integer program. The most difficult case is where the objective
parameters are bilinear, and we prove its complexity is NP-hard even under simplifying assumptions. We consider a relaxation
that provides an approximation, giving an overall guarantee of near-optimality when used with branch-and-bound search. We
present preliminary computational experiments that illustrate the computational complexity of solving these robust formulations
on sensor placement applications. 相似文献
119.
Robins NP Figl C Haine SA Morrison AK Jeppesen M Hope JJ Close JD 《Physical review letters》2006,96(14):140403
In this Letter we present experimental results and a simple analytic theory on the first continuous (long pulse) Raman atom laser. We analyze the flux and brightness of a generic two state atom laser with an analytic model that shows excellent agreement with our experiments. We show that, for the same source size, the brightness achievable with a Raman atom laser is at least 3 orders of magnitude greater than achievable in any other demonstrated continuously outcoupled atom laser. 相似文献
120.
John C. Morrison Timothy Wolf Bernard Bialecki Graeme Fairweather Lee Larson 《Molecular physics》2013,111(16):1175-1184
A basis of Hermite splines is used in conjunction with the collocation method to solve the orbital equations for diatomic molecules. Accurate solutions of the Hartree-Fock equations are obtained using iterative methods over most regions of space, while solving the equations by Gaussian elimination near the nuclear centres. In order to improve the speed and accuracy of our iterative scheme, a new self-adjoint form of the Hartree-Fock equation is derived. Using this new equation, our iterative subroutines solve the Hartree-Fock equations to one part in 106. The Gaussian elimination routines are accurate to better than one part in 108. 相似文献