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1.
The effects of varying the sampler-skimmer spacing in an inductively coupled plasma-mass spectrometer are illustrated. The signals for a number of species were monitored including background ions (ArN +, ArO +, ArOH +, Ar 2+, Ar 2H +), background continuum, analyte ions (Cu +, Ce +, La +), analyte oxide ions (CeO +, LaO +), and matrix induced ions (ArNa +). As the sampler-skimmer spacing is increased over that normally used, the signal for some species decreases in intensity while the signal for others increases in intensity. There is a wide range of differential behavior and in some cases the signal changes are quite dramatic. In addition to presenting results for an Ar plasma, measurements are also presented for a N2-Ar mixed gas plasma. For some species, the signal changes observed when the sampler-skimmer spacing is increased are quite different with the N2-Ar mixed gas plasma than with the Ar plasma and are, in some cases, opposite to signal changes observed with the Ar plasma. It appears that a larger sampler-skimmer spacing is more appropriate for a N2 mixed gas plasma than the spacing normally used for a pure Ar plasma. Finally the effect of sampler-skimmer spacing on matrix effects is presented and it appears that matrix effects are not induced in the zone between the sampler and the skimmer. 相似文献
2.
The effects of adding N 2 to the outer gas flow of an Ar plasma in inductively coupled plasma mass spectrometry (ICP-MS) are illustrated. With 5% N 2 added to the outer gas flow and provided the central (nebulizer) gas flow is increased, modest signal enhancements (up to a factor of 4) are observed. The degree of enhancement depends on the extent to which an element forms a strong metal oxide bond and also, to some extent, on ionization potential. An important feature of N 2 mixed gas plasmas for ICP-MS is that the signals for analyte oxide species (MO +) and certain background species (ArO +, ArOH +, Ar 2+, ClO +, and ArCl +) are significantly reduced (an order of magnitude) by the addition of N 2 to the outer gas flow. In addition to these observations, some results are also presented for O 2 and air (outer gas) mixed gas plasmas and N 2 (central gas) mixed gas plasmas. 相似文献
3.
The six A′ potential energy surfaces were computed by a DIM-like method involving a valence-bond quasidiabatic basis. Transition dipole moments were also determined using a similar method. The 4D dynamics of this system (restricted to a molecular plane fixed in space) was obtained with the HWD method (hemiquantal dynamics with the whole DIM basis) and the visible photoabsorption spectrum was determined with the help of a 1D full quantum mechanical program applied to each normal mode. The photoabsorption spectrum of Ar 3+ was calculated in the range 440–710 nm. It corresponds to photodissociation since the excited Ar 3+ ions almost all dissociate into the Ar + +Ar+Ar channel by a rapid explosion of the cluster, and only very few into Ar 2+ +Ar. It is dominated by a transition to the second excited state along with a symmetric stretching motion. We found a prominent 80 nm wide peak centered at 530 nm, with a maximum cross section of 4.2 × 10 −16cm 2. The Ar 2+ formation results from a transition to the first excited state under low-energy laser excitation and is controlled by non-adiabatic transitions. 相似文献
4.
Rovibrational spectra of H 3+, HN 2+, and H 3O + generated in discharge jet-expansion have been studied using a difference-frequency infrared source. The rotational temperatures were determined to be 120 ± 20, 273 ± 20 and 150 ± 20 K for H 3+, HN 2+, and H 3O +, respectively. Some dynamic phenomena of the jet-discharges are also discussed. 相似文献
5.
采用分子动力学方法研究了铀酰在叶腊石表面的吸附和扩散。在碳酸根离子存在的情况下,探究了温度对铀酰吸附和扩散的影响。碳酸根离子与铀酰存在较强的作用力,不同数目的碳酸根离子与铀酰结合会形成多种铀酰种态。在不同温度的模拟中,得到了UO_2~(2+)、UO_2CO_3、UO_2(CO_3)_2~(2-)、UO_2(CO_3)_3~(4-)四种铀酰种态和铀酰聚合物。通过原子密度图,观察了粒子在溶液中的分布情况。发现UO_2~(2+)+和UO_2CO_3容易吸附在叶腊石上,而UO_2(CO_3)_2~(2-)和UO_2(CO_3)_3~(4-)主要存在于扩散层中。随着时间的推移,越来越多的碳酸根离子与铀酰配位,使得铀酰在叶腊石上的吸附逐渐减少。本文计算了不同温度下,各铀酰种态的扩散系数。在扩散层中,各种态的扩散系数随温度的变化较为一致,而在吸附层中,UO_2~(2+)和UO_2CO_3的扩散速率随温度的变化较UO_2(CO_3)_2~(2-)和UO_2(CO_3)_3~(4-)慢。但是在同一温度下,同一个吸附层或扩散层中,铀酰种态的扩散系数大小顺序始终保持不变:UO_2~(2+)UO_2CO_3UO_2(CO_3)_2~(2-)UO_2(CO_3)_3~(4-)。说明在碳酸根存在的情况下,UO_2~(2+)可能是主要的扩散形式。 相似文献
6.
The ionization and dissociative ionization of NF 3 by electron impact has been measured by Fourier transform mass spectrometry (FTMS). The total ionization cross-section rises to a maximum value of 2.4±0.4×10 −16 cm 2 at 140 eV. Estimates of the total single ionization cross-section using ab initio energies with the binary encounter Bethe (BEB) [Y.K. Kim, M.E. Rudd, Phys. Rev. A 50 (1994) 3594] or Deutsch–Märk [Int. J. Mass Spec. 197 (2000) 37] models are roughly twice the measured values. The partial cross-sections creating NF x+ ( x=0, 1, 2, 3), F +, and NF x2+ ( x=1, 2, 3) are reported. Differences between the FTMS results and quadrupole data and fast atom beam results of Tarnovsky et al. [Int. J. Mass Spectrom. Ion Processes 133 (1994) 175] are discussed. 相似文献
7.
将无机盐K 3PO 4、K 2HPO 4和KH 2PO 4作为活化剂,分别添加于氨基乙酸盐溶液中,形成CO 2活化吸收剂,采用膜接触器 再生循环装置,评价和比较了氨基乙酸盐和活化吸收剂捕集CO 2的性能,研究了活化剂的浓度、气液流速等因素对总体积传质系数、传质通量和捕集率的影响。结果表明,磷酸盐活化剂在氨基乙酸盐吸收剂中,对CO 2的捕集均产生影响,活化效应存在PO 43->HPO 42->H 2PO 4-的规律;添加少量活化剂的作用比添加较多量的活化作用大;活化吸收剂的捕集率明显大于非活化吸收剂;膜吸收流体力学状态的改变,能够改善膜接触器传质性能,增大传质通量,但增大的程度有限。 相似文献
8.
A method which couples a model Hamiltonian to hemiquantal dynamics is proposed as a general theoretical treatment of multistate molecular processes. A test application to the Ar 3+ system is performed which involves four nuclear degrees of freedom and six quasidiabatic states. The method proves efficient for dealing with non-adiabatic transitions occurring at singularities like conical intersections and avoided crossings between potential surfaces. 相似文献
9.
近年来,对金属簇的研究已成为化学与物理学中最活跃的研究领域之一[1].金属簇被认为是介于单个原子与固体之间的中间相[2].深入地研究其结构、形成机理及物理与化学行为,对于寻找新的催化剂[3],重新认识气相化学与凝聚相化学的关系[4],都有非常重要的意... 相似文献
10.
采用催化加氢的方式将CO 2转化为甲醇,既可以减少CO 2排放,又制备了化学品,该反应具有重要的研究意义.氧化铟(In 2O 3)作为CO2加氢制甲醇催化剂,由于其较高的CO 2活化能力和甲醇选择性,被科研工作者广泛研究.其中,将具有良好解离H2能力的过渡金属元素引入In 2O 3(M/In 2O 3)是有效提高催化剂性能的策略之一,然而,M/In 2O 3体系催化CO 2加氢反应机理及活性位点仍不清楚.本文引入Co制备了In-Co二元金属氧化物催化剂应用于CO2加氢制甲醇,结果表明,相较于In 2O 3,In-Co催化剂性能有很大提升,其中In1-Co 4催化剂上甲醇时空产率(9.7 mmol·g cat-1 h -1)是In 2O 3(2.2 mmol·g cat-1 h -1)的近5倍(反应条件:P=4.0 MPa,T=300℃,GHSV=24000 cm 3 STP g cat-1 h -1,H2/CO 2=3).值得注意的是,尽管Co是金属元素的主体,In-Co催化剂中Co催化CO 2甲烷化的活性受到明显抑制.本文还通过多种技术系统研究了催化剂结构与反应选择性转变间的关系.采用电感耦合等离子体发射光谱、粉末X射线衍射、拉曼光谱、X射线光电子能谱和透射电子显微镜等对催化剂结构以及表面性质进行了表征.结果表明,在H 2还原气氛诱导下,In-Co催化剂表面发生重构,形成以CoO为核,以In 2O 3为壳的核壳结构,其在高压反应后仍能保持稳定;更重要的是,该核壳结构可以显著增强In-Co催化剂吸附及活化CO 2的能力.CO 2加氢反应动力学研究表明,Co催化剂上H 2分压对CO 2加氢为零级反应,而H 2分压在In-Co上的反应级数为正数;In-Co催化剂上,CO 2分压的反应级数接近于零,表明CO 2及其衍生物在In-Co的表面吸附饱和,但在纯Co上,则不会发生这种饱和吸附.通过原位DRIFTS研究了催化反应路径和关键中间物种的吸附及反应行为,发现CO 2加氢在纯Co和In-Co上的催化机理均遵循甲酸盐路径.在该催化路径中,CO 2首先加氢为甲酸盐(*HCOO)物种,随后加氢为甲氧基(*CH 3O).*CH 3O在Co催化剂上进一步加氢生成CH 4,而*CH 3O在In-Co催化剂上则会脱附生成CH 3OH.根据表征结果,本文认为,在还原性气氛下,In-Co发生了重构并生成表面富In 2O 3的核壳状结构,显著提高了催化剂对CO 2和含碳物种的吸附能力.Co和In-Co催化剂对CO 2加氢反应选择性的差异归因于催化剂对CO 2和对*HCOO等含碳中间物种的吸附稳定性不同.CO 2及其衍生的含碳中间物种在In-Co催化剂上的吸附能力比在Co催化剂上强,形成了较合适的催化剂表面C/H比,从而使*CH 3O能够脱附为CH 3OH,而不是进一步加氢为CH 4.综上,本文研究为高活性In-Co催化剂体系在CO 2加氢反应中的催化机理及行为提供了解释,为金属-氧化铟(M-In 2O 3)催化剂体系的设计提供了参考. 相似文献
11.
The laser excitation spectrum of the Br 2+ molecular ion was observed at rotational resolution for the first time, with the ions being generated by Penning ionization. In contrast to Cl 2+ and F 2+ but in agreement with recent theoretical work, no vibrational or rotational perturbations are observed. The data from a number of vibrational bands are fitted simultaneously to give reliable estimates of the Dunham rotational and vibrational constants. This fit indicates that the vibrational numbering used in previous studies should be increased by 1 in the upper state. 相似文献
12.
采用高温固相法制备了系列Zn改性的层状K-Fe-Zn-Ti催化剂,用于CO 2加氢经费托合成直接制烯烃反应。采用SEM、TEM、XRD、H 2-TPR、CO 2-TPD、XPS、N 2吸附-脱附和TG等手段对反应前后的催化剂进行了表征,对K-Fe-Zn-Ti催化剂的组成-结构-性能关系进行了关联研究。结果表明,所制备的催化剂均出现K 2.3Fe 2.3Ti 5.7O 16物相,为典型的层状金属氧化物(Layered Metal Oxides,LMO)结构;Zn改性后生成了ZnFe 2O 4物相,降低了催化剂样品结晶度,增强了表面碱性,促进了CO 2表面吸附。在CO 2加氢反应中,K-Fe-Zn-Ti系列催化剂均具有较高的烯烃选择性(O/P>6.5),Zn改性促进了C 5+的生成,显著提高了C 4+线性α-烯烃(linear α-olefins,LAOs)的选择性,C 4+烃中LAOs含量由Zn改性前的54.6%提高至75.2%。在所考察的范围内,随Zn/Fe比的增加,烯/烷比(C 2-4=/C 2-40,O/P)先增加后降低,但对重烃含量以及LAOs选择性影响不明显。K-Fe-Zn-Ti催化剂具有较好的稳定性,经100 h在线反应后,仍保持LMO结构。 相似文献
13.
利用同步辐射真空紫外光电离结合飞行时间质谱对五氟乙烷(CHF 2CF 3)进行了光电离光解离的研究,测定了CHF 2CF 3的电离势及该分子主要碎片离子的出现势. 结果表明: CHF 2CF 3的绝热电离势为(12.25±0.10) eV, 主要碎片离子有CF 2CF 3+、CHFCF3+、CF2CF2+、CF3+、CHF2+、CHF+和CF+,其出现势分别为 (13.93±0.10) eV, (15.25±0.10) eV, (15.12±0.10) eV, (13.30±0.05) eV, (13.05±0.08) eV, (19.17±0.10) eV和 (19.56±0.15) eV. 另外,用从头算分子轨道理论计算了解离电离过程中所有碎片的总能量,并给出了电子态及对称性. 根据实验结果和理论计算,分析了可能的解离通道,并得到了分子及母体离子的键解离能等重要的热力学数据. 相似文献
14.
采用催化加氢的方式将CO 2转化为甲醇,既可以减少CO 2排放,又制备了化学品,该反应具有重要的研究意义.氧化铟(In 2O 3)作为CO2加氢制甲醇催化剂,由于其较高的CO 2活化能力和甲醇选择性,被科研工作者广泛研究.其中,将具有良好解离H2能力的过渡金属元素引入In 2O 3(M/In 2O 3)是有效提高催化剂性能的策略之一,然而,M/In 2O 3体系催化CO 2加氢反应机理及活性位点仍不清楚.本文引入Co制备了In-Co二元金属氧化物催化剂应用于CO2加氢制甲醇,结果表明,相较于In 2O 3,In-Co催化剂性能有很大提升,其中In1-Co 4催化剂上甲醇时空产率(9.7 mmol·g cat-1 h -1)是In 2O 3(2.2 mmol·g cat-1 h -1)的近5倍(反应条件:P=4.0 MPa,T=300℃,GHSV=24000 cm 3 STP g cat-1 h -1,H2/CO 2=3).值得注意的是,尽管Co是金属元素的主体,In-Co催化剂中Co催化CO 2甲烷化的活性受到明显抑制.本文还通过多种技术系统研究了催化剂结构与反应选择性转变间的关系.采用电感耦合等离子体发射光谱、粉末X射线衍射、拉曼光谱、X射线光电子能谱和透射电子显微镜等对催化剂结构以及表面性质进行了表征.结果表明,在H 2还原气氛诱导下,In-Co催化剂表面发生重构,形成以CoO为核,以In 2O 3为壳的核壳结构,其在高压反应后仍能保持稳定;更重要的是,该核壳结构可以显著增强In-Co催化剂吸附及活化CO 2的能力.CO 2加氢反应动力学研究表明,Co催化剂上H 2分压对CO 2加氢为零级反应,而H 2分压在In-Co上的反应级数为正数;In-Co催化剂上,CO 2分压的反应级数接近于零,表明CO 2及其衍生物在In-Co的表面吸附饱和,但在纯Co上,则不会发生这种饱和吸附.通过原位DRIFTS研究了催化反应路径和关键中间物种的吸附及反应行为,发现CO 2加氢在纯Co和In-Co上的催化机理均遵循甲酸盐路径.在该催化路径中,CO 2首先加氢为甲酸盐(*HCOO)物种,随后加氢为甲氧基(*CH 3O).*CH 3O在Co催化剂上进一步加氢生成CH 4,而*CH 3O在In-Co催化剂上则会脱附生成CH 3OH.根据表征结果,本文认为,在还原性气氛下,In-Co发生了重构并生成表面富In 2O 3的核壳状结构,显著提高了催化剂对CO 2和含碳物种的吸附能力.Co和In-Co催化剂对CO 2加氢反应选择性的差异归因于催化剂对CO 2和对*HCOO等含碳中间物种的吸附稳定性不同.CO 2及其衍生的含碳中间物种在In-Co催化剂上的吸附能力比在Co催化剂上强,形成了较合适的催化剂表面C/H比,从而使*CH 3O能够脱附为CH 3OH,而不是进一步加氢为CH 4.综上,本文研究为高活性In-Co催化剂体系在CO 2加氢反应中的催化机理及行为提供了解释,为金属-氧化铟(M-In 2O 3)催化剂体系的设计提供了参考. 相似文献
15.
Photocatalytic reduction of CO2(CO2PR)to valuable solar fuels is considered as a promising route to the amelioration of fossil fuel conundrum and the mitigation of greenhouse gases.Although progress has been made to enhance CO2PR performance,the available method that can promote the selectivity of CO2PR products remains to be a challenge.In this work,we synthesized NO3-or CO32-intercalated NiAl-layered double hydroxide(NiAl-LDH)photocatalysts and investigated the performance of CO2PR in the presence of an electron donor and a photosensitizer.Compared with Ni2Al-CO32-,Ni2Al-NO3-exhibited superior catalytic performance in the CO2PR,and the resulted selectivity of CH4 in Ni2Al-NO3-(6.1%)was 12.2 times that of Ni2Al-CO32-(0.5%)under visible light irradiation.X-Ray absorption fine structure(XAFS)result reveals a relative abundance of defects in Ni2Al-NO3-,which played as active sites and promoted charge transfer in CO2PR for the efficient CH4 evolution. 相似文献
16.
用共沉淀法合成了以钴为主的水滑石型化合物(HTLc),用XRD、IR等对其及热分解产物进行了表征。结果表明,水滑石经过焙烧,逐渐失去层间的H 2O、OH -和CO 32-,转化成尖晶石结构。比表面积测定和CO 2-TPD结果表明,焙烧温度和产物的Co:Cu比对表面积和碱性均有明显的影响。 相似文献
17.
The distribution behavior of ion associates (Q +) 2. TeBr 62− of TeBr 62− with quaternary ammonium cations (Q +) between aqueous phase and two organic phases (1,2-dichloroethane (DCE) and chloroform (CF)) was examined, and the extraction constants (log K ex) were determined. The extractability with long-chain alkyltrimethylammonium cations (group I) is greater than that with symmetrical tetraalkylammonium cations (group II) in the 1,2-dichloroethane extraction system and the difference in log K ex for two cations (one of each type) with the same number of carbon atoms was about 3 on the average. The contributions of a methylene group in the cations of groups I and II to log K ex were found to be 0.431.10 and about 0.74 on the average. Among the ion associates examined, the extractability of the extracting solvent was in the DCE>CF; the difference in log K ex was about 5 on the average. 相似文献
18.
Under the public spotlight, uranyl (UO 22+) ions has attracted considerable attention for the extreme radioactive and chemical toxicity to ourselves and our environment. Herein, we present a simple and effective ratiometric fluorescence imaging method for the visualizing and quantitative detection UO 22+ ions by cellphone-based optical platform. The sensing solution was prepared by mixing label-free red carbon dots (r-CDs) and blue carbon dots (b-CDs) together with a fixed photoluminescence intensity ratio of 4:1. When UO 22+ ions were added, the fluorescence of r-CDs can be selectively quenched, while the fluorescence of b-CDs remains stable without spectral changes. With the gradually increase the amounts of UO 22+ ions, the different response of dual-color CDs resulted in a signification color evolution from deep red to dark purple under the ultraviolet (UV) light illumination. Then, a cellphone-based optical platform was constructed for directly imaging the color change of the samples, and the built-in Colorpicker APP quickly output the red, green and blue (RGB) channel values of these images within one second. Interesting, there was a linear relationship between the ratio of red and blue (R/B) channel values and UO 22+ ions concentration from 0 μmol/L to 30.0 μmol/L ( R2 = 0.92804) with the detection limit of ~8.15 μmol/L (signal-to-noise ratio of 3). In addition, the optical platform has also been applied to the quantification of UO 22+ ions in tap water and river water sample. With the advantage of low-cost, portable, easy to operation, we anticipate that this method would greatly improve the accessibility of UO 22+ ions detection even in resource-limited areas. 相似文献
19.
A tandem quadrupole mass spectrometer is used to study the charge transfer reactions NH 3+ + NO and NO + + NH 3 over a collision energy range 1.5–13 eV. The vibrational state of the reagent ions is selected by resonance-enhanced multiphoton ionization. For the 0.9 eV exothermic process NH 3+ + NO → NH 3 + NO + excitation of the v2 umbrella bending mode ( v2 = 0–12) causes no marked change in the charge transfer cross section, while in the reverse process NO + + NH 3 → NO + NH 3+ excitation of the NO + vibration ( v = 0–6) strongly enhanced the charge transfer cross section. 相似文献
20.
The influence of charge on the thermal dissociation of gaseous, protonated, homodimeric, protein ecotin ions produced by nanoflow electrospray ionization (nanoES) was investigated using the blackbody infrared radiative dissociation technique. Dissociation of the protonated dimer, (E 2 + nH) n+ E 2n+ where n = 14–17, into pairs of monomer ions is the dominant reaction at temperatures from 126 to 175 °C. The monomer pair corresponding to the most symmetric charge distribution is preferred, although 50–60% of the monomer product ions correspond to an asymmetric partitioning of charge. The relative abundance of the different monomer ion pairs produced from E 214+, E 215+, and E 216+ depends on reaction time, with the more symmetric charge distribution pair dominating at longer times. The relative yield of monomer ions observed late in the reaction is independent of temperature indicating that proton transfer between the monomers does not occur during dissociation and that the different monomer ion pairs are formed from dimer ions which differ in the distribution of charge between the monomers. For E 217+, the yield of monomer ions is independent of reaction time but does exhibit slight temperature dependence, with higher temperatures favoring the monomers corresponding to most symmetric charge distribution. The charge distribution in the E 215+ and E 216+ dimer ions influences the dissociation kinetics, with the more asymmetric distribution resulting in greater reactivity. In contrast, the charge distribution has no measurable effect on the dissociation kinetics and energetics of the E 217+ dimer. 相似文献
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