共查询到20条相似文献,搜索用时 31 毫秒
1.
Cheng J Kozole J Hengstebeck R Winograd N 《Journal of the American Society for Mass Spectrometry》2007,18(3):406-412
The sputtering properties of two representative cluster ion beams in secondary ion mass spectrometry (SIMS), C(60)(+) and Au(3)(+), have been directly compared. Organic thin films consisting of trehalose and dipalmitoylphosphatidylcholine (DPPC) are employed as prototypical targets. The strategy is to make direct comparison of the response of a molecular solid to each type of the bombarding cluster by overlapping the two ion beams onto the same area of the sample surface. The ion beams alternately erode the sample while keeping the same projectile for spectral acquisition. The results from these experiments are important to further optimize the use of cluster projectiles for SIMS molecular depth profiling experiments. For example, Au(3)(+) bombardment is found to induce more chemical damage as well as Au implantation when compared with C(60)(+). Moreover, C(60)(+) is found to be able to remove the damage and the implanted Au effectively. Discussions are also presented on strategies of enhancing sensitivity for imaging applications with cluster SIMS. 相似文献
2.
Kéki S Nagy L Deák G Zsuga M Somogyi L Lévai A 《Journal of the American Society for Mass Spectrometry》2004,15(6):879-883
It was found earlier that under matrix-assisted laser desorption/ionization (MALDI) conditions several organic compounds which produce adduct with silver ions, are also capable of forming adducts with Ag(3)(+) cluster ions under appropriate conditions. The Ag(3)(+) cluster ion can be in situ generated under the MALDI analysis conditions from silver trifluoroacetate cationization agent in the presence of organic MALDI matrices. In this article the fragmentation of a commercial plasticizer, a peracetylated isoflavone glycoside and a pyrazolylphenyl disulfide derivative cationized with silver ions and Ag(3)(+) cluster ions are compared. It was observed that the complexes of Ag(3)(+) are less fragmented than the corresponding adduct ions with Ag(+). The presumable fragmentation channel of [M + Ag(3)(+)] is the elimination of Ag(2) units from these complexes. No significant dissociation of [M + Ag(3)(+)], into M and Ag(3)(+) takes place, indicating a tight connection between the corresponding molecule and Ag(3)(+) cluster ion. However, with a compound carrying very labile groups, such as the pyrazolylphenyl disulfide derivative, intramolecular cleavages can occur prior to significant dissociation of the Ag(3)(+) cluster ion. 相似文献
3.
Postawa Z Czerwinski B Winograd N Garrison BJ 《The journal of physical chemistry. B》2005,109(24):11973-11979
Molecular dynamics computer simulations have been employed to model the bombardment of Ag{111} covered with three layers of C6H6 by 15 keV Ga and C60 projectiles. The study is aimed toward examining the mechanism by which molecules are desorbed from surfaces by energetic cluster ion beams and toward elucidating the differences between cluster bombardment and atom bombardment. The results show that the impact of the cluster on the benzene-covered surface leads to molecular desorption during the formation of a mesoscopic scale impact crater via a catapulting mechanism. Because of the high yield of C6H6 with both Ga and C60, the yield enhancement is observed to be consistent with related experimental observations. Specific energy and angle distributions are shown to be associated with the catapult mechanism. 相似文献
4.
Conlan XA Lockyer NP Vickerman JC 《Rapid communications in mass spectrometry : RCM》2006,20(8):1327-1334
Ion bombardment of pure water ice by Au+ monoatomic and Au3 + and C60 + polyatomic projectiles results in the emission of two series of water cluster ions-(H2O)n + and (H2O)nH+-with n ranging from 1 to >40. The cluster ion yields are very significantly higher under polyatomic ion bombardment than when using an Au+ primary ion. The yield of the protonated water species (H2O)nH+ is found to be enhanced by increasing ion fluence. C60 + bombardment results in a very dramatic increase in the (H2O)nH+ yield and decrease in the yield of (H2O)n +. Au3 + also significantly increased the yield of protonated species relative to the non-protonated but to a lesser extent than C60 +. Bombardment by Au+ also increased the yield of protonated species but to a very much smaller extent. The hypothesis that the protonated species may enhance the yield of [M+H]+ from solute molecules in solution has been investigated using two amino acids, alanine and arginine, and a nucleic base, adenine. The data suggest that the protons produced by the sputtering of water ice are depleted in the presence of these solutes and concurrently the yields of solute-related [M+H]+ and immonium secondary ions are greatly enhanced. These yield enhancements are analysed in the light of other possible contributors such as increased rates of sputtering under polyatomic beams and increased secondary ion yields as a consequence of solute dispersion. It is concluded that enhanced proton attachment is occurring in polyatomic sputtered frozen aqueous solutions. 相似文献
5.
E. S. Zakaria 《Journal of Radioanalytical and Nuclear Chemistry》2005,264(3):629-635
Summary This paper reports the radiochemical study of the ion-exchange of Cs+, Na+, Sr2+ and Eu3+ ions with H+ by chromium hexacyanoferrate(II) which was prepared in a granular form using a gel method. The slow steps which determine the rate of exchange of these ions are directly proportional to the particle diameter and this is confirmed from the linearity test of Bt vs. t plots at different particle diameters. Boyed’s equation and Reichenberg’s tables were used for evaluating all the kinetic parameters. The results reveal that the effective particle radii are unchanged for both chromium hexacyanoferrate(II) dried at 60 and 120 °C. The obtained data were analyzed using McKay plots and Arrhenius equation and the kinetic and thermodynamic parameters, e.g., effective diffusion coefficient, activation energies and entropies of activation have been evaluated. The mobility of these ions inside the particles of chromium hexacyanoferrate(II) decrease in the order of Eu3+>Sr2+>Na+⊃Cs+. 相似文献
6.
《Surface and interface analysis : SIA》2004,36(10):1367-1372
We have investigated the merits of fullerene cluster ions as projectiles in time‐of‐flight secondary neutral mass spectrometry (ToF‐SNMS) sputter depth profiling of an Ni:Cr multilayer sample similar to the corresponding NIST depth profiling standard. It is shown that sputter erosion under bombardment with C60+ ions of kinetic energies between 10 and 20 keV provides good depth resolution corresponding to interface widths of several nanometres. This depth resolution is maintained during the complete removal of the multilayer stack with a total thickness of 500 nm. This finding is in contrast to the case where atomic Ga+ projectile ions of comparable kinetic energy are used, demonstrating the unique features of cluster projectiles in sputter depth profiling. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
7.
S. V. Shevkunov 《Colloid Journal》2010,72(1):93-106
Charge separation in “soft” nanoparticles composed of water molecules, as well as sodium and chlorine ions, is studied by computer simulation. The detailed model of intermolecular interactions that includes, in addition to Coulomb, exchange, and dispersion forces, many-particle polarization and covalent interactions, as well as the effect due to the transfer of excess ion charges and influence of ion field on molecular interactions, is constructed. Model potentials are calibrated using experimental data on the free energy and enthalpy of the addition of vapor molecules to the hydration shells of ions, as well as the data of quantum-chemical calculations for stable cluster configurations and the vibration frequency of interionic bonds. The allowance for many-particle interactions makes it possible to improve the agreement between experimental and quantum-chemical data by more than an order of magnitude. The disregard for many-particle interactions leads to the significant overestimation of cluster stability. 相似文献
8.
S. V. Shevkunov 《Colloid Journal》2010,72(1):107-124
Charge separation in “soft” nanoparticles composed of water molecules, as well as sodium and chlorine ions, is studied by
computer simulation. The detailed model of intermolecular interactions that includes, in addition to Coulomb, exchange, and
dispersion forces, many-particle polarization and covalent interactions, as well as the effect due to the transfer of excess
ion charges and influence of ion field on molecular interactions, is constructed. Model potentials are calibrated using experimental
data on the free energy and enthalpy of the addition of vapor molecules to the hydration shells of ions, as well as the data
of quantum-chemical calculations for stable cluster configurations and the vibration frequency of interionic bonds. The allowance
for many-particle interactions makes it possible to improve the agreement between experimental and quantum-chemical data by
more than an order of magnitude. The disregard for many-particle interactions leads to the significant overestimation of cluster
stability. 相似文献
9.
Yu. V. Larichev B. L. Moroz E. M. Moroz V. I. Zaikovskii S. M. Yunusov E. S. Kalyuzhnaya V. B. Shur V. I. Bukhtiyarov 《Kinetics and Catalysis》2005,46(6):891-899
The Ru-Cs+/MgO and Ru-Cs+/γ-Al2O3 catalysts, which were prepared by an impregnation method using RuOHCl3 and Cs2CO3 as precursor compounds and reduced with H2 at 450°C, are characterized by X-ray diffraction, high-resolution transmission electron microscopy (with X-ray microanalysis), and X-ray photoelectron spectroscopy (XPS). The Cs+/MgO(Al2O3) systems, Ru-Cs+ black, and model systems prepared by cesium sputtering onto polycrystalline ruthenium foil are studied as reference samples. It is found that, in the Ru-Cs+/MgO sample, cesium is present as a Cs2 + xO cesium suboxide, which weakly interacts with the support, localized on the surface of Ru particles or near them. In the case of Ru-Cs+/γ-Al2O3, cesium occurs as a species that is tightly bound to the support; this is likely surface cesium aluminate, which prevents promoter migration to Ru particles. The Ru-Cs+/MgO sample exhibits a considerable shift of the Ru3d line in the XPS spectra toward lower binding energies, as compared to the bulk metal. It is hypothesized that this shift is due to a decrease in the electron work function from the surface of ruthenium because of the polarizing effect of Cs+ ions in contact with Ru particles. Based on the experimental results, the great difference between the catalytic activities of the Ru-Cs+/MgO and Ru-Cs+/γ-Al2O3 systems in ammonia synthesis at 250–400°C and atmospheric pressure is explained. 相似文献
10.
Van Royen P Taranu A Van Vaeck L 《Rapid communications in mass spectrometry : RCM》2005,19(4):552-560
Static secondary ion mass spectrometry (S-SIMS) emerges as one of the most adequate methods for the surface characterisation of polymers with an information depth of essentially one monolayer. The continuing search for increased analytical sensitivity and specificity has led to exploring the use of polyatomic primary ions as an alternative to the traditionally applied monoatomic projectiles. As part of a systematic investigation on polyatomic bombardment of organic and inorganic solids, this paper focuses on selected polyesters. Mass spectra and ion yields are compared for layers deposited on silicon wafers by spincoating solutions with different concentrations of poly(epsilon-caprolactone) (PCL), poly(butylene adipate) (PBA) and poly(ethylene adipate) (PEA). Accurate mass measurements have been used to support the assignment of the ions and link the composition of the detected ions to the analyte structure. Use of polyatomic projectiles increases the yield of structural ions with a factor of +/-15, +/-30 and +/-10 for PCL, PBA and PEA, respectively, in comparison to bombardment with Ga+ primary ions, while the molecular specificity is improved by the detection of additional high m/z ions. 相似文献
11.
Boschmans B Van Royen P Van Vaeck L 《Rapid communications in mass spectrometry : RCM》2005,19(18):2517-2527
The application of polyatomic primary ions is a strongly developing branch of static secondary ion mass spectrometry (S-SIMS), since these projectiles allow a significant increase in the secondary ion yields to be achieved. However, the different limitations and possibilities of certain polyatomic primary ions for use on specific functional classes of samples are still not completely known. This paper compares the use of monoatomic and polyatomic primary ions in S-SIMS for thin layers of polylactic acid (PLA), obtained by spin-coating solutions on silicon wafers. Bombardment with Ga+, Xe+ and SF5+ primary ions allowed the contribution of the projectile mass and number of atoms in the gain in ion yield and molecular specificity (relative importance of high m/z and low m/z signals) to be assessed. Samples obtained by spin-coating solutions with increasing concentration showed that optimal layer thickness depended on the primary ion used. In comparison with the use of Ga+ projectiles, the yield of structural ions increased by a factor of about 1.5 to 2 and by about 7 to 12 when Xe+ and SF5+ primary ion bombardment were applied, respectively. A detailed fragmentation pattern was elaborated to interpret ion signal intensity changes for different projectiles in terms of energy deposition and collective processes in the subsurface, and the internal energy of radical and even-electron precursor ions. 相似文献
12.
De Mondt R Van Vaeck L Heile A Arlinghaus HF Nieuwjaer N Delcorte A Bertrand P Lenaerts J Vangaever F 《Rapid communications in mass spectrometry : RCM》2008,22(10):1481-1496
Static secondary ion mass spectrometry (S-SIMS) is one of the potentially most powerful and versatile tools for the analysis of surface components at the monolayer level. Current improvements in detection limit (LOD) and molecular specificity rely on the optimisation of the desorption-ionisation (DI) process. As an alternative to monoatomic projectiles, polyatomic primary ion (P.I.) bombardment increases ion yields non-linearly. Common P.I. sources are Ga+ (liquid metal ion gun (LMIG), SF5+ (electron ionisation) and the newer Au(n)+, Bi(n)q+ (both LMIG) and C60+ (electron ionisation) sources. In this study the ion yield improvement obtained by using the newly developed ion sources is assessed. Two dyes (zwitterionic and/or thermolabile polar functionalities on a largely conjugated backbone) were analysed as a thin layer using Ga+, SF5+, C60+, Bi+, Bi3(2+) and Bi5(2+) projectiles under static conditions. The study aims at evaluating the improvement in LOD, useful and characteristic yield and molecular specificity. The corrected total ion count values for the different P.I. sources are compared for different instruments to obtain a rough estimate of the improvements. Furthermore, tentative ionisation and fragmentation schemes are provided to describe the generation of radical and adduct ions. Characteristic ion yields are discussed for the different P.I. sources. An overview of the general appearances of the mass spectra obtained with the different P.I. sources is given to stress the major improvement provided by polyatomic P.I.s in yielding information at higher m/z values. 相似文献
13.
D. V. Vrazhnov T. A. Kochina A. A. Alferova I. S. Ignat’ev 《Russian Journal of General Chemistry》2011,81(6):1131-1136
B3LYP method with the LANL2DZ basis for tin and aug-cc-pVDZ basis for carbon and hydrogen were used to obtain the equilibrium
geometry of the main (with a positive charge on the tin) isomers in the C4H11Sn+ system and the transition states at their interconversion. As in the case of silicon and germanium, the cations of lighter
elements of the 14th group, the most stable isomer is shown to be the tertiary ion, however, the energy of its complexes with
ethane and propane is higher only by several kJ mol−1. Nevertheless, the formation of these complexes from the tertiary ion requires overcoming a rather high barrier (293 and
272 kJ mol−1, respectively). The barrier for isomerization of the secondary ion in the ethane complex is somewhat lower (222 kJ mol−1), but still is significantly greater than the energy gained at the appearance of the nucleogenic ion. The most probable transformation
pathways of the nucleogenic stannylium ions are the formation of complexes with ethylene, which requires overcoming barriers
of 130 and 117 kJ mol−1 for the tertiary and secondary ions, respectively. 相似文献
14.
B. V. Slobodin L. L. Surat B. V. Shulgin A. N. Cherepanov A. V. Ishchenko R. F. Samigullina F. G. Neshov 《Russian Journal of Inorganic Chemistry》2009,54(10):1543-1550
Rhombohedral hexametavanadates K4Sr(VO3)6, K4Ba(VO3)6, Rb4 Ba(VO3)6, and Cs4Ba(VO3)6 melt incongruently in the temperature range of 491 to 600°C. Cooling of peritectic melts yields mixtures of compounds typical
of M2+O-M2+O-V2O5 systems, far from equilibrium and depending on the cooling kinetics. The vanadate Cs4Ba(VO3)6 undergoes reversible polymorphic transformation at 360°C. All compounds show broad-band luminescence with a maximum of the
luminescence spectrum at 490–590 nm with three types of excitation. The vanadates K4Sr(VO3)6 and Rb4Ba(VO3)6 show the highest luminescence intensity at room temperature. The latter is also most efficient at liquid nitrogen temperatures.
The luminescence spectra depend on the excitation of vanadates. Three hypotheses were put forward to interpret this finding.
The nature of luminescence is attributed to the relaxation of electronic excitation in [VO4]3− structural tetrahedra present in the vanadates. The performance characteristics of luminophores were determined. These luminophores
may be promising as X-ray luminescent screens, radioluminescence indicators, and light-emitting diode devices. 相似文献
15.
E. Yu. Safronova V. I. Volkov A. A. Pavlov A. V. Chernyak E. V. Volkov A. B. Yaroslavtsev 《Russian Journal of Inorganic Chemistry》2011,56(2):156-162
The hydration, state, and mobility of protons and Li+, Na+, and Cs+ ions in MF-4SK perfluorinated sulfonic acid cation-exchange membranes doped with silicon dioxide and phosphotungstic acid
have been investigated by NMR and impedance spectroscopy. The dopants increase the moisture content of the membrane and change
the system of pores and channels in which ion transport takes place. At low humidities, the dopant particles are involved
in ion transport. The greatest effect is observed for the membranes doped with both SiO2 and phosphotungstic acid. The water molecules sorbed by dopant particles as a material participate in the hydration of alkali
metal cations in the membrane. 相似文献
16.
Hudson CE Bowen RD McAdoo DJ 《Journal of the American Society for Mass Spectrometry》2008,19(1):27-32
Most H2 eliminations from cations in the gas phase are formally 1,1- or 1,2- processes. Larger ring size H2 eliminations are rare and little studied. Thus, whether the 6-center, 1,4- elimination CH3CH=N+HCH3-->CH2=CHN+H=CH2+H2 is concerted and synchronous, as indicated by isotope effects and predicted by conservation of orbital symmetry, is a significant question. This reaction is characterized here by application of QCI and B3LYP theories. CH bond-breaking and H-H bond-making in this reaction are found by theory to be highly synchronized, consistent with previously established isotope effects and in contrast to "forbidden" 1,2-eliminations from organic cations in the gas phase. This reaction is made feasible by its conservation of orbital symmetry, the energy supplied by formation of the H-H bond, and a favorable geometry of the ion for eliminating H2. 相似文献
17.
Ranjini Raghunandan Fabio J. Mazzotti John P. Maier 《Journal of the American Society for Mass Spectrometry》2010,21(5):694-697
Measurement of the 3Π-3Π transition of C6H+ in the gas phase near 19486 cm−1 is reported. The experiment was carried out with a supersonic slit-jet expansion discharge using cavity ringdown absorption
spectroscopy. Partly resolved P lines and observation of band heads permitted a rotational contour fit. Spectroscopic constants
in the ground and excited-state were determined. The density of ions being sampled is merely 2×108 cm−3. Broadening of the spectral lines indicates the excited-state lifetime to be ≈100 ps. The electronic transition of HC6H2+ at 26402 cm−1 assumed to be 1A1-X1A1 in C2v symmetry could not be rotationally resolved. 相似文献
18.
Han-Bai Quan Liang-Bing Sheng Hua-Hong Zou Zi-Yuan Liu Dong-Cheng Liu Bo Li Man-Sheng Chen Fu-Pei Liang 《Journal of Cluster Science》2018,29(1):75-81
A series of twist linear tetranuclear 3d–4f Co 2 III Ln 2 III [Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5)] complexes have been prepared under solvothermal conditions and structurally characterized with Schiff-base ligand 2-(((2-hydroxy-3-methoxyphenyl)methylene)amino)-2-(hydroxymethyl)-1,3-propanediol (H4L). The two central Co ions are linked by two alkoxyl oxygen atoms, and one Ln ion lying above and the other below the Co–Co dimer, form a twist linear array. The magnetic susceptibility studies reveal antiferromagnetic or ferromagnetic behaviour, whilst dynamic magnetic studies indicate no slow magnetic relaxation for these complexes. 相似文献
19.
S. V. Shevkunov 《Colloid Journal》2011,73(2):275-286
The Gibbs energy and equilibrium work of the formation of nuclei of the condensed phase on sodium ions are calculated on the
molecular level by a Monte Carlo simulation using a detailed interaction model. The stationary rate of nucleation is estimated
based on the data obtained. The presence of ionic impurities only substantially affects the rate of nucleation at strong vapor
supersaturation. The nucleus losses its thermodynamic stability with an increase in the size of the nucleus and the barrier
is formed depending on the work of formation on the size of the nucleus. An abrupt loss of stability is accompanied by pushing
the ion off of the microdroplet surface and the restoration of the network of hydrogen bonds. The effect of pushing an ion
to the surface of a cluster greatly depends on many-particle polarization interactions. 相似文献
20.
Moon HK Wells DD Gardella JA 《Journal of the American Society for Mass Spectrometry》2012,23(1):23-29
This study reports the characteristic fragmentation patterns from two polysiloxane polymers that form ordered overlayer on
silver substrates. Results are compared for the bombardment of various monatomic and polyatomic projectiles of Cs+, C60+ (10 keV), Bi1+, and Bi3+ (25 keV) in the high mass range time-of-flight secondary ion mass spectrometry (TOF-SIMS) spectra. Results are reported from
sub-monolayer (solution cast) coverages of poly(dimethylsiloxane)s with the number average molecular weights (Mn) of 2200 and 6140 Da, respectively, and Langmuir-Blodgett monolayers of poly(methylphenylsiloxane) with molecular weights
(MW) from 600 and 1000 Da. For each film, Bi projectiles resulted in the emission of positive silver cluster ions from the
substrate under the polymer overlayer and peaks corresponding to silver cluster ions with larger mass were observed by impact
of polyatomic 25 keV Bi3+ projectiles. In addition, depending on the change of energy of Bi3+, a different pattern of fragments was observed. With Cs+ and C60+ impact, however, the emission of silver cluster ions was not detected. In the case of C60+ impact for PDMS-6140, peaks corresponding to silver-cationized intact oligomers were not observed. In this paper, these results
are explained by the possible bombardment mechanism for each projectile, based on its mass, energy, and split trajectories
of the component atoms under the polyatomic impact. 相似文献