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131.
The interaction of low-energy electrons with multilayers of SiCl(4) adsorbed on Si(111) leads to production and desorption of Cl((2)P(32)), Cl((2)P(12)), Si, and SiCl. Resonant structure in the yield versus incident electron energy (E(i)) between 6 and 12 eV was seen in all neutral channels and assigned to dissociative electron attachment (DEA), unimolecular decay of excited products produced via autodetachment and direct dissociation. These processes yield Cl((2)P(32)) and Cl((2)P(12)) with nonthermal kinetic energies of 425 and 608 meV, respectively. The Cl((2)P(12)) is produced solely at the vacuum surface interface, whereas the formation of Cl((2)P(32)) likely involves subsurface dissociation, off-normal trajectories, and collisions with neighbors. Structure in the Cl((2)P(32)) yield near 14 and 25 eV can originate from excitation of electrons in the 2e, 7t(2) and 6t(2), 6a(1) levels, respectively. Although the 14 eV feature was not present in the Cl((2)P(12)) yield, the broad 25 eV feature, which involves complex Auger filling of holes in the 6t(2) and 6a(1) levels of SiCl(4), is observed. Direct ionization, exciton decay, and DEA from secondary electron scattering all occur at E(i)>14 eV. Si and SiCl were detected via nonresonant ionization of SiCl(x) precursors that are produced via the same states and mechanisms that yield Cl. The Si retains the kinetic energy profile of the desorbed precursors. 相似文献
132.
A.O. Evans E.S. Paul A.J. Boston H.J. Chantler C.J. Chiara M. Devlin A.M. Fletcher D.B. Fossan D.R. LaFosse G.J. Lane I.Y. Lee A.O. Macchiavelli P.J. Nolan D.G. Sarantites J.M. Sears A.T. Semple J.F. Smith K. Starosta C. Vaman A.V. Afanasjev I. Ragnarsson 《Physics letters. [Part B]》2006
Three strongly coupled sequences have been established in 110,112Te up to high spins. They are interpreted in terms of deformed structures built on proton 1-particle–1-hole excitations that reach termination at I∼40?. This is the first observation of smooth terminating dipole structures in this mass region. Lifetime measurements have allowed the extraction of experimental B(M1;I→I−1) and B(E2;I→I−2) reduced transition rates for one of the dipole bands in 110Te. The results support the deformed interpretation. 相似文献
133.
Ultrafast laser pulses on Ir{111} cause a highly temperature-dependent redshift of the intramolecular stretch frequency of adsorbed NO. The time-resolved spectral changes are driven by charge transfer of hot electrons to the NO 2pi*d antibonding orbital, which leads to bending of NO and internal bond weakening. The nonadiabatic change in the NO adsorption geometry follows the charge transfer within a time scale of 700 femtoseconds. This geometrical change is the same as the mechanism predicted for thermally induced dissociation. 相似文献
134.
Ambrosio M Antolini R Auriemma G Baker R Baldini A Bam B Barbarino GC Barish BC Battistoni G Bellotti R Bemporad C Bernardini P Bilokon H Bisi V Bloise C Bower C Bussino S Cafagna F Calicchio M Campana D Carboni M Corona A Cecchini S Cei F Chiarella V Cormack R Coutu S DeCataldo G Dekhissi H DeMarzo C De Vincenzi M Di Credico A Diehl E Erriquez O Favuzzi C Forti C Fusco P Giacomelli G Giannini G Giglietto N Grassi M Green P Grillo A Guarino F Guarnaccia P Gustavino C Habig A Heinz R Hong JT 《Physical review D: Particles and fields》1994,50(5):3046-3058
135.
Leitch MJ Boissevain J Carey TA Jansen DM Jeppesen RG Kapustinsky JS Lane DW Lillberg JW McGaughey PL Moss JM Peng JC Isenhower LD Sadler ME Schnathorst R Gidal G Ho PM Kowitt MS Luk KB Pripstein D Lederman LM Schub MH Brown CN Cooper WE Glass HD Gounder KN Mishra CS Kaplan DM Luebke WR Martin VM Preston RS Sa J Tanikella V Childers R Darden CW Wilson JR Chen YC Kiang GC Teng PK 《Physical review letters》1994,72(16):2542-2545
136.
Interest in hair analysis as an alternative or complementary approach to urinalysis for drug abuse detection has grown in recent years. Hair analysis can be particularly advantageous for drugs such as amphetamine and methamphetamine that are rapidly excreted. Confirmation of abuse of these stimulants is complicated by the fact that some forms are found in legitimate medications. Examination of the enantiomeric composition of amphetamine and methamphetamine in hair samples can provide valuable assistance in interpreting drug testing results. In this work, we developed a liquid chromatographic method for the separation of amphetamine and methamphetamine enantiomers isolated from human hair samples. The drug enantiomers were separated on a chiral stationary phase after derivatization with an achiral fluorescent agent. The methodology was evaluated with a Standard Reference Material that contained several drugs of abuse including amphetamine and methamphetamine.Contribution of the National Institute of Standards and Technology. Not subject to copyright. 相似文献
137.
[formula: see text] A highly diastereoselective synthesis of 3, corresponding to the C(5)-C(21) segment of tedanolide, has been accomplished by a route utilizing the aldol reaction of aldehyde 4 and the beta,gamma-unsaturated methyl ketone 5. 相似文献
138.
139.
Stephen?A.?WiseEmail author Katherine?E.?Sharpless Lane?C.?Sander Willie?E.?May 《Accreditation and quality assurance》2004,9(9):543-550
To address the measurement and standard needs of the food and nutrition communities, the National Institute of Standards and Technology (NIST) has developed a suite of food-matrix Standard Reference Materials (SRMs) characterized for nutrient concentrations. These food-matrix SRMs include infant formula, baby food, and typical diet composites; meat homogenate, oyster, mussel, and fish tissues; baking chocolate; peanut butter; and spinach. Many of these materials were developed based on recommendations of the food industry to populate a nine-sectored triangle, developed by the Association of Analytical Communities (AOAC) International, in which foods are positioned based on their fat, protein, and carbohydrate contents. Value assignment of proximates, vitamins, and elements of nutritional interest in these food-matrix SRMs has been based primarily on the combination of results from measurements at NIST and from a group of collaborating laboratories involved in food measurements. Food-matrix SRMs are now available that are representative of all nine sectors of the AOAC International food-matrix triangle. Current activities are focused on the development of SRMs for dietary supplements including botanical and multivitamin/multielement materials.Presented at the CCQM Workshop on Comparability and Traceability in Food Analysis, 18–19 November 2003, BIPM, Sèvres, France. 相似文献
140.
The kinetics of the reactions O(3P) + CF2CCl2 and O(3P) + CF3CFCF2 were studied at room temperature in a discharge flow tube system. The overall rate constants based on the measured afterglow reactions were (3.10 ± 0.40) × 10−13 and (3.00 ± 0.60) × 10−14 cm3 molecule−1 s−1, respectively. The experiments were carried out under pseudo‐first‐order conditions with [O(3P)]0 ≪ [alkene]0. These results are compared with previous relative measurements using different experimental techniques. The effect of substituent atoms or groups on the overall rate constants is analyzed in comparison with other alkenes in the literature. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 867–872, 1999 相似文献