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1.
Kiuchi M Matsumoto T Yoshikawa T Goto S Ensinger W 《Colloids and surfaces. B, Biointerfaces》2000,19(3):269-273
To investigate crystallization in the ion beam deposition process, titanium ions were deposited on silicon wafers at 105 and 55 eV. As titanium is an active metal, titanium compounds are formed by absorbing backfilled or residual gas. At energy levels of 105 or 55 eV, titanium crystallizes in a NaCl-type titanium compound with the backfilling of air. In all samples, (110)-oriented crystals grew with a rectangular lattice arrangement of titanium atoms. The open channel <110> of preferentially oriented crystal growth was parallel to the direction of incident ions normal to the substrate surface. 相似文献
2.
Cumulant functions are introduced to describe the statistical state of a radiation field. These functions are simply related
to the optical coherence functions but have some interesting features. It is shown that if the cumulant functions of all orders
greater than some numberN
0 vanish then they also vanish for all orders greater than 2. Thermal field is the only field having this property. This property
holds whether the field is described by a classical stochastic process or by a quantum density operator. Further the particular
operator ordering used in defining these cumulant functions for the quantized field affects only the second order cumulant
function. To describe the statistical state of a vector field such as partially polarized or unpolarized radiation, one would
need to introduce cumulant tensors. 相似文献
3.
Mass Spectra of Alkoxistibanes The mass spectra of the methoxistibanes Sb(OMe)3 ( 1 ), ClSb(OMe)2 ( 2 ) and Cl2SbOMe ( 3 ) and of d9-triethoxistibane ( 4 ) are measured at 20 and 70 eV. The fragmentation processes as well as the fragmentation mechanisms which explaines the formation of Sb? H fragments are discussed. 相似文献
4.
MA Freitas CL Hendrickson AG Marshall 《Rapid communications in mass spectrometry : RCM》1999,13(15):1639-1642
We present a novel approach for the determination of activation energy for the unimolecular dissociation of a large (>50 atoms) ion, based on measurement of the unimolecular dissociation rate constant as a function of continuous-wave CO(2) laser intensity. Following a short ( approximately 1 s) induction period, CO(2) laser irradiation produces an essentially blackbody internal energy distribution, whose 'temperature' varies inversely with laser intensity. The only currently available method for measuring such activation energies is blackbody infrared radiative dissociation (BIRD). Compared with BIRD, FRAGMENT: (a) eliminates the need to heat the surrounding ion trap and vacuum chamber to each of several temperatures (each requiring hours for temperature equilibration); (b) offers a three-fold wider range of effective blackbody temperature; and (c) extends the range of applications to include initially cold ions (e.g., gas-phase H/D exchange). Our FRAGMENT-determined activation energy for dissociation of protonated bradykinin, 1.2 +/- 0.1 eV, agrees within experimental error to the value, 1.3 +/- 0.1 eV, previously reported by Williams et al. from BIRD experiments. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
5.
Mass Spectra of Dialkylaminostibanes . The dialkylaminostibanes Cl2SbNMe2 (1), ClSb(NMe2)2 (2), Sb(NMe2)3 (3), Sb(NEt2)3 (4), and ClSbOMeNMe2 (5) were examined by mass spectrometry. The mass spectra were discussed and mechanisms and pathes of fragmentation proposed. 相似文献
6.
An LC-MS method for the determination of picric acid (2,4,6-trinitrophenol), its reductive transformation products picramic acid (2-amino-4,6-dinitrophenol) and iso-picramic acid (4-amino-2,6-dinitrophenol) and hexyl (2,2',4,4',6,6'-hexanitrodiphenylamine) has been developed. The analytes were separated using ion-pairing chromatography with a volatile ion-pairing reagent suitable for subsequent MS detection. The performance of an atmospheric pressure chemical ionisation (APCI) and an electrospray ionisation (ESI) interface was compared. ESI-MS is more sensitive for the analytes, especially for hexyl and picric acid, APCI-MS delivered more fragments necessary for unequivocal identification. With LC-ESI-MS limits of detection using single ion monitoring (SIM) mode are 4 ng (iso-picramic acid), 800 pg (picramic acid), 400 pg (picric acid) and 80 pg (hexyl). For quantification, 15N-picric acid was used as an internal standard. Using this new method, the degradation of picric acid in soil was monitored in a laboratory study. Furthermore, the presence of picramic acid was for the first time verified in soil samples from a former ammunition plant. 相似文献
7.
Baake O Hoffmann PS Flege S Ortner HM Gottschalk S Berky W Balogh AG Ensinger W Beckhoff B Kolbe M Gerlach M Pollakowski B Weser J Ulm G Haschke M Blokhina E Peter M Porta D Heck M 《Analytical and bioanalytical chemistry》2009,393(2):623-634
Multilayered samples consisting of Al, Co and Ni nanolayers were produced by MBE and characterized nondestructively by means
of SRXRF, μ-XRF, WDXRF, RBS, XRR, and destructively with SIMS. The main aims were to identify the elements, to determine their
purity and their sequence, and also to examine the roughness, density, homogeneity and thickness of each layer. Most of these
important properties could be determined by XRF methods, e.g., on commercial devices. For the thickness, it was found that
all of the results obtained via XRR, RBS, SIMS and various XRF methods (SRXRF, μ-XRF, WDXRF) agreed with each other within
the limits of uncertainty, and a constant deviation from the presets used in the MBE production method was observed. Some
serious preliminary discrepancies in the results from the XRF methods were examined, but all deviations could be explained
by introducing various corrections into the evaluation methods and/or redetermining some fundamental parameters. 相似文献
8.
V. P. Perelygin I. G. Abdullaev G. P. Knyazeva L. I. Kravets R. I. Petrova R. Brandt W. Ensinger P. Vater R. L. Fleischer Yu. V. Bondar M. Rebetez 《Radiation measurements》2003,36(1-6):271-279
The unique approach for search and unambiguous identification of short-lived (T1/2=103–107 years) superheavy nuclei in cosmic-ray products of the recent nucleosynthesis in our Galaxy are discussed.It is based on: (a) the ability of non-conducting crystals to register and to store for many million years the tracks due to fast nuclei with atomic number Z20 (“fossil” tracks);(b) calibrations of the said crystals with accelerated heavy ions (20Z92) and on revealing the volume etchable track length (VETL) of the fast nuclei coming to rest inside crystals—both of fossil and “fresh” tracks—to determine the charge distribution of cosmic-ray nuclei tracks and(c) the so-called “four-zone” model of tracks in crystals (and also glasses) which provides not only the VETL track length dependence for 20Z92 nuclei but also demonstrates the regular annealing behavior of VETL of 20Z92 nuclei in a broad temperature interval.This approach was first applied in the early 1980s to investigate the “fossil” tracks due to 22Z92 cosmic-ray nuclei in olivine crystals from meteorites-pallasite Marjalahti and Eagle Station.The discovery of Th–U cosmic-ray nuclei tracks in 1980 was unambiguously confirmed by calibrations of the same crystals with 238U, 197Au and 208Pb accelerated ions in the late 1980s. More than 1600 tracks due to cosmic-ray actinide nuclei were measured during the last two decades of the 20th century.Also, 11 anomalously long tracks (track length exceeds by a factor (1.6±0.1) the track length due to Th–U nuclei were measured. The detailed analysis shows that at least 5 of these tracks could not be attributed to the Th–U nuclei. It means that now we have a preliminary proof on the existence Z110 nuclei in cosmic-rays. The abundance is Z110/Th–U=(1–3)×10−3 in Z110 freshly formed cosmic-rays (time interval 103–107 years).The method proposed can provide the necessary and sufficient conditions for the discovery of Z110 nuclei in nature. 相似文献
9.
Chemical interactions in the layered system BC
x
N
y
/Ni(Cu)/Si, produced by CVD at high temperature
Hoffmann PS Kosinova MI Flege S Baake O Pollakowski B Trunova VA Klein A Beckhoff B Kuznetsov FA Ensinger W 《Analytical and bioanalytical chemistry》2012,404(2):479-487
Layered samples Si(100)/C/Ni/BC(x)N(y) and Si(100)/C/Cu/BC(x)N(y) were produced by physical vapor deposition of a metal (Ni, Cu, resp.) and low-pressure chemical vapor deposition of the boron carbonitride on a Si(100) substrate. Between the Si and the Ni (Cu) and on the surface of the Ni (Cu) layer, thin carbon layers were deposited, as a diffusion barrier or as a protection against oxidation, respectively. Afterwards, the surface carbon layer was removed. As precursor, trimethylamine borane and, as an auxiliary gas, H(2) and NH(3) were used, respectively. The chemical compositions of the layers and of the interfaces in between were characterized by total-reflection X-ray fluorescence spectrometry combined with near-edge X-ray absorption fine-structure spectroscopy, X-ray photoelectron spectroscopy, and secondary ion mass spectrometry. The application of H(2) yielded the BC(x)N(y) compound whereas the use of NH(3) led to a mixture of h-BN and graphitic carbon. At the BC(x)N(y)/metal interface, metal borides could be identified. At the relatively high synthesis temperature of 700 °C, broad regions of Cu or Ni and Si were observed between the metal layer and the substrate Si. 相似文献
10.
Kuehne ME Bornmann WG Markó I Qin Y LeBoulluec KL Frasier DA Xu F Mulamba T Ensinger CL Borman LS Huot AE Exon C Bizzarro FT Cheung JB Bane SL 《Organic & biomolecular chemistry》2003,1(12):2120-2136
Sixty-two congeners of vinblastine (VLB), primarily with modifications of the piperidine ring in the carbomethoxycleavamine moiety of the binary alkaloid, were synthesized and evaluated for cytotoxicity against murine L1210 leukemia and RCC-2 rat colon cancer cells, and for their ability to inhibit polymerization of microtubular protein at < 10(-6) M, and for induction of spiralization of microtubular protein, and for microtubular disassembly at 10(-4) M concentrations. An ID50 range of >10(7) M concentrations was found for L1210 inhibition by these compounds, with the most active 1000x as potent as vinblastine. 相似文献