Macroscopic jumps of the axial angular momentum variance of a bidimensionally trapped ion

Abstract

The time evolution of the axial angular momentum [Lcirc] _z of an ion confined in a bidimensional trap is investigated. We find that, under suitable initial conditions, the interaction of the ion with two properly configured classical laser beams induces a peculiar dynamical behaviour of the axial angular momentum fluctuations. We show, in fact, that there exists an instant of time at which the variance of [Lcirc] _z undergoes variations proportional to N ² further to a change of one quantum only in the initial total number N ? 1 of vibrational quanta. The non-classical origin of these macroscopic jumps is brought to the light and carefully discussed.     

Positive ion transmission mode ion/ion reactions in a hybrid linear ion trap

A triple quadrupole mass spectrometer capable of ion trapping experiments has been adapted for ion/ion reaction studies. The instrument is based on a commercially available linear ion trap (LIT) tandem mass spectrometer (i.e., an MDS SCIEX 2000 Q TRAP) that has been modified by mounting an atmospheric sampling glow discharge ionization (ASGDI) source to the side of the vacuum manifold for production of singly charged anions. The ASGDI source is located line of sight to the side of the third quadrupole of the triple quadrupole assembly (Q3). Anions are focused into the side of the rod array (i.e., anion injection occurs orthogonal to the normal ion flight path). A transmission mode method to perform ion/ion reactions has been developed whereby positive ions are transmitted through the pressurized collision quadrupole (Q2) while anions are stored in Q2. The Q2 LIT is used to trap negative ions whereas the Q3 LIT is used to accumulate positive ions transmitted from Q2. Anions are injected to Q3 and transferred to Q2, where they are stored and collisionally cooled. Multiply charged protein/peptide ions, formed by electrospray, are then mass selected by the first quadrupole assembly (Q1) operated in the rf/dc mode and injected into Q2. The positive ions, including the residual precursor ions and the product ions arising from ion/ion proton-transfer reactions, are accumulated in Q3 until they are analyzed via mass-selective axial ejection for mass analysis. The parameters that affect ion/ion reactions are discussed, including pressure, nature of the gas in Q2, and operation of Q2 as a linear accelerator. Ion/ion reactions in this mode can be readily utilized to separate ions with the same m/z but largely different mass and charge, e.g., +1 bradykinin and +16 myoglobin, in the gas phase.     

Experimental preparation and measurement of quantum states of motion of a trapped atom

Abstract

We report the creation and full determination of several quantum states of motion of a ⁹Be⁺ ion bound in a RF (Paul) trap. The states are coherently prepared from an ion which has been initially laser cooled to the zero-point of motion. We create states having both classical and non-classical character including thermal, number, coherent, squeezed, and ?Schrödinger cat‘ states. The motional quantum state is fully reconstructed using two novel schemes that determine the density matrix in the number state basis or the Wigner function. Our techniques allow well controlled experiments decoherence and related phenomena on the quantum-classical borderline.     

A family of exact eigenstates for a single trapped ion interacting with a laser field

Abstract

We show that, under certain combinations of the parameters governing the interaction of a harmonically trapped ion with a laser beam, it is possible to find one or more exact eigenstates of the Hamiltonian, with no approximations except the optical rotating-wave approximation. These are related via a unitary equivalence to exact eigenstates of the full Jaynes-Cummings model (including counter-rotating terms) supplemented by a static driving term.     

Physical properties of a trapped two-level ion decaying by thermal and squeezed vacuum reservoirs

In this paper, we first study the interaction between a trapped two-level ion with a field reservoir in a general form. Then, we use thermal and squeezed vacuum reservoirs to continue our investigation. We try to find the equation of motion for the whole system density operator by applying the Weisskopf theory. Next, we evaluate the explicit form of the density matrix elements analytically. In the obtained density matrix elements, we arrive at some physical parameters of the trapped ion system as well as the applied field reservoirs by which one can control the transition probabilities between the trapped ionic states. We also introduce some hermitian operators for the trapped ion system and calculate the expectation values of their time evolution by considering the mentioned two reservoirs. In the continuation, we design a system for measuring the hermitian trapped ion’s operators theoretically. Finally, we find a way to transport the information of the trapped ion system by our proposed quantum processor.     

Thermal evolution of trapped gas from extended subsurface layers during a linear tempering schedule

Numerical computer calculations for the thermal evolution of gas trapped by defects in extended subsurface layers of solids or coatings under a linear tampering schedule have been carried out. The dependence of the shape and location of thermal evolution transients upon the extension (width) of the initially trapped gas distribution has been found in comparison with the case of an initial planar concentration of trapped gas some lattice units below the surface. A comparative study has been performed concerning the effect of the thermal release mechanism (for ‘tandem’ and pure diffuisve mechanism) upon the thermal evolution transients having a given initial extended distribution and specific ratios of the migration energy to detrapping energy.     

Performance of a linear ion trap-Orbitrap hybrid for peptide analysis

Proteomic analysis of digested complex protein mixtures has become a useful strategy to identify proteins involved in biological processes. We have evaluated the use of a new mass spectrometer that combines a linear ion trap and an Orbitrap to create a hybrid tandem mass spectrometer. A digested submandibular/sublingual saliva sample was used for the analysis. We find the instrument is capable of mass resolution in excess of 40,000 and mass measurement accuracies of less than 2 ppm for the analysis of complex peptide mixtures. Such high mass accuracy allowed the elimination of virtually any false positive peptide identifications, suggesting that peptides that do not match the specificity of the protease used in the digestion of the sample should not automatically be considered as false positives. Tandem mass spectra from the linear ion trap and from the Orbitrap have very similar ion abundance ratios. We conclude this instrument will be well suited for shotgun proteomic types of analyses.     

Dual electrospray ion source for electron-transfer dissociation on a hybrid linear ion trap-orbitrap mass spectrometer

A dual electrospray ionization source (ESI) has been modified to simultaneously produce cations and anions, one from each emitter, for performing rapid electron-transfer dissociation (ETD) ion/ion reactions on a hybrid linear ion trap-orbitrap mass spectrometer. Unlike the pulsed dual ESI sources that were used to generate ETD reagent ions, this source separates the emitters in space, rather than time, by physically switching which one is in front of the atmospheric inlet. The new arrangement allows for substantially enhanced spray stability and decreased switching times (相似文献   

展向剪切流作用下斜置圆柱气动特性研究

采用大涡模拟方法,研究斜置圆柱在展向剪切流作用下的气动性能。研究了不同剪切流强度对斜置圆柱的表面风压、Strouhal数、气动力时程及其功率谱、气动力展向相关性等气动性能的影响,并探讨了剪切流对斜圆柱气动性能的作用机理。结果表明:在均匀流作用下,斜置圆柱尾流区会产生强烈的轴向流,卡门涡脱强度大大减弱;展向剪切流对斜置圆柱的表面风压和气动力等气动性能有较大影响;展向剪切流会破坏轴向流在斜置圆柱尾流区的形成,并且当剪切流的剪切系数足够大时,可完全阻止轴向流的出现,从而减弱或消除了抑制卡门涡脱的因素,恢复了斜置圆柱的卡门涡脱强度。     

Implementation of electron-transfer dissociation on a hybrid linear ion trap-orbitrap mass spectrometer

We describe the adaptation of a hybrid quadrupole linear ion trap-orbitrap mass spectrometer to accommodate electron-transfer ion/ion reactions (ETD) for peptide and protein characterization. The method utilizes pulsed, dual electrospray ion sources and requires minimal instrument modification. Switching between cation and reagent anion injection schemes is automated and accomplished within a few hundred milliseconds. Ion/ion reactions are conducted within the linear ion trap, after which the c- and z-type product ions are passed to the orbitrap for high-resolution m/z analysis. With this arrangement, mass accuracies are typically measured to within 2 ppm at a resolving power of approximately 60 000. Using large peptides and intact proteins, we demonstrate such capabilities will accelerate our ability to interrogate high-mass species. To illustrate compatibility with automated data-dependent analysis and subsequent data processing, we couple the technique with an online chromatographic separation of a yeast whole-cell lysate followed by peptide identification using ProSight PC. Fairly long pulsing times and relatively low ET efficiency, as compared to conventional ETD instrumentation, are the main drawbacks of this approach. Still, our results suggest that the implementation of ETD on sensitive, high-resolution, and high-mass accuracy hybrid instrumentation, such as the orbitrap, will substantially propel the emergent fields of middle- and top-down proteomics.     

Performance evaluation of a hybrid linear ion trap/orbitrap mass spectrometer

Design and performance of a novel hybrid mass spectrometer is described. It couples a linear ion trap mass spectrometer to an orbitrap mass analyzer via an rf-only trapping quadrupole with a curved axis. The latter injects pulsed ion beams into a rapidly changing electric field in the orbitrap wherein they are trapped at high kinetic energies around an inner electrode. Image current detection is subsequently performed after a stable electrostatic field is achieved. Fourier transformation of the acquired transient allows wide mass range detection with high resolving power, mass accuracy, and dynamic range. The entire instrument operates in LC/MS mode (1 spectrum/s) with nominal mass resolving power of 60,000 and uses automatic gain control to provide high-accuracy mass measurements, within 2 ppm using internal standards and within 5 ppm with external calibration. The maximum resolving power exceeds 100,000 (fwhm). Rapid, automated data-dependent capabilities enable real-time acquisition of up to three high-mass accuracy MS/MS spectra per second.     

一种新型离子交换纤维材料的制备及其应用

以在极端的环境中仍具有良好的稳定性和完整性的聚四氟乙烯纤维为基体，通过共辐照接枝苯乙烯单体，而后把接枝纤维氯甲基化、胺化，制备出一种高交换容量、高机械强度、高热稳定性、耐腐蚀、抗氧化的强碱型离子交换纤维材料。对辐照纤维、接枝纤维、氯甲基化纤维及最终产品纤维从化学结构、机械性能、热稳定性、吸附性能、吸附容量等方面进行了表征。材料的拉伸伸长率、拉伸强度保持良好；5％热失重温度高，可以在400℃左右的温度下长期工作；最大静态吸附容量达6．08mmol／g。新型材料对于酸性气体CO2有良好的吸附脱除作用。     

圆柱壳稳定性分析的一种新方法

针对圆柱壳在复杂栽荷作用下静力稳定性问题提出了一种新的求解方法．基于分离变量的方法，设定一组可涵盖任意边界条件的复数位移函数，将位移函数代入系统平衡方程后，圆柱壳的静力稳定性问题就可以转化为一个复系数八次多项式的求根问题．该特征方程的偶次幂系数项以及常数项为实数，而奇数次幂项均为纯虚数．研究表明，根的大小代表了圆柱壳端部作用力的强度，以及该作用力在离开这个边界一定距离上的衰减特性．分析了该新方法和经典方法的关系，并给出了一个各向同性圆柱壳在轴向压力作用下稳定性分析算例，得到了线弹性失稳解．和经典方法的结果比较表明，文中所提出的新方法适用可行，且和经典方法具有同样的精度．     

Polarimetric investigation of materials with both linear and circular anisotropy

Abstract

We investigate light propagation through materials with both linear and circular anisotropy and find the relation of the amplitude and polarization transfer functions to the four anisotropic characteristics: linear circular birefringence, and linear and circular dichroism. We determine these four characteristics of anisotropic samples by measuring the output intensity and polarization corresponding to different input polarization azimuths and fitting the theoretical and experimental results. In our experiments we have used films of side-chain azobenzene polyesters in which optical anisotropy had been previously induced on illumination with elliptically polarized light.     

■100mm金刚石小圆锯片的研制及应用

本文提出■100mm金刚石小圆锯片的最佳配方,最佳金刚石粒度和生产工艺,制成了锋利和耐磨的锯片,并应用于石头建材和陶瓷等的加工。     

φ100mm金刚石小圆锯片的研制及应用

本文提出φ100mm金刚石小圆锯片的最佳配方,最佳金刚石粒度和生产工艺,制成了锋利和耐磨的锯片,并应用于石头建材和陶瓷等的加工.     

Solutions of multiple crack problems of a circular plate or an infinite plate containing a circular hole by using Fredholm integral equation approach

Presented is an elementary solution, which is a particular solution of the circular plate containing one crack. The solution consists of two parts and satisfies the following conditions: (i) the first part corresponds to a pair of normal and tangential concentrated forces acting at a prescribed point on both edges of a single crack; (ii) the second part corresponds to some distributed tractions along both edges of the crack; (iii) the obtained elementary solution, i.e. the sum of the first and second parts, satisfies a traction free condition on the circular boundary. Using this elementary solution and taking some undetermined density of the elementary solution along each crack, a system of Fredholm integral equations of multiple crack problems can always be obtained. The multiple crack problems of an infinite plate containing a circular hole can be solved in a similar way. Several numerical examples are given in this paper.