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121.
L. Corner J.S. Gibb G. Hancock A. Hutchinson V.L. Kasyutich R. Peverall G.A.D. Ritchie 《Applied physics. B, Lasers and optics》2002,74(4-5):441-444
We have used a violet diode laser at 404 nm and a distributed feedback diode laser at 1320 nm to produce 0.8 nW of radiation
at 309 nm by sum frequency generation in beta-barium borate. The UV radiation was tuned mode-hop-free over 30 GHz and used
to detect OH radicals produced in a microwave discharge. By chopping the UV light at 500 Hz, we observed a concentration of
2×1012 cm-3 with a signal to noise ratio of 30:1.
Received: 16 November 2001 / Revised version: 23 January 2002 / Published online: 14 March 2002 相似文献
122.
Accurate and efficient integration of the electron density function over arbitrary regions has been previously achieved by exploiting a separation of variables. Recently, a computer program has been written that calculates ρ, \documentclass{article}\pagestyle{empty}\begin{document}$ \buildrel{\rightharpoonup}\over{\nabla} $\end{document}ρ, and ?2ρ in an expeditious fashion, taking advantage of the separation of variables in the electron density function. Accurate integrations of ?2ρ over arbitrary regions can also be accomplished. The structure of the program is suited especially to vector processors. As a result of the efficiencies of these programs, functions of the electron density, such as the density itself, the surrounding electrostatic potential, ?ρ, and ?2ρ have been calculated in three dimensions. Results of calculations for nitrated cubanes are presented illustrating how the effects of the nitro groups are manifested in the electron density and associated properties. 相似文献
123.
In this paper, we introduce the notions of (∈, ∈∨q)-fuzzy subnear-ring, (∈, ∈∨q)-fuzzy ideal and (∈, ∈∨q)-fuzzy quasi-ideal of near-rings and find more generalized concepts than those introduced by others. The characterization of such (∈, ∈ ∨q)-fuzzy ideals are also obtained. 相似文献
124.
125.
R.B. Ekanayake J.M. Norman E. Ritchie P.H. Smith B.R. Taylor P. Wilcox 《European Journal of Operational Research》1977,1(4):225-229
A case study for the design of a spare parts inventory control system is described. The main emphasis is given to the problems of applying and tailoring forecasting and inventory control theory to suit the needs of a particular problem. In the main, well established methods were used and these are not described in detail. New developments arising in the course of the study have been described elsewhere. 相似文献
126.
127.
The potassium salts of two new hepta coordinated oxyfluoro anions of tungsten (VI) are reported in this paper. The monomer, K3WO2F5 was obtained from the aqueous solution while the dimer, K6W2O5F8 was isolated from alcohol. The absorption peak of K6W2O5F8 at 830 cm-1 has been attributed to W-O-W link. The W-O-W angle is found to be 155° and the force constant is 4.44 mdyn/A°. The d values obtained from x-ray powder diffraction studies are given. 相似文献
128.
The purpose of this study was to assess the effectiveness of two generative learning strategies, concept mapping and laboratory experiments involving object manipulation, to determine if either one is more‐effective with individual learners or learning groups in a science classroom. Eighty sixth‐grade science‐students were randomly assigned to group or individual conditions and to one of two experimental treatments. Experimental treatments were changed between a first and second posttest. Long‐term retention was evaluated with a third, delayed posttest. Students starting with concept maps showed higher achievement on the delayed posttest than students beginning with the laboratory experiment. No difference was found between students working as individuals or in groups, but a significant interaction between generative learning strategy and grouping condition was revealed. Implications for sequencing generative learning strategies are discussed. 相似文献
129.
R. J. Walker J. Kirkbride J. H. van Helden D. Weidmann G. A. D. Ritchie 《Applied physics. B, Lasers and optics》2013,112(2):159-167
The linewidth of an external cavity quantum cascade laser is studied as a function of injection current and laser scan rate. The laser linewidth is inferred to be ca. 2.5 MHz from Lamb-dip spectra on a low pressure sample of NO and its variation with injection current is well modeled using literature values for the intrinsic material properties of the lasing medium. The laser linewidth measurements are corroborated by polarization spectroscopy studies as well as by analysis of hyperfine structure and cross-over resonances. 相似文献
130.