eV Collision Energy Research Articles

Application of gas chromatography-tandem mass spectrometry (GC/MS/MS) for the analysis of deuterium enrichment of water.

Incorporation of deuterium from deuterium oxide ((2) H2 O) into biological components is a commonly used approach in metabolic studies. Determining the dilution of deuterium in the body water (BW) pool can be used to estimate body composition. We describe three sensitive GC/MS/MS methods to measure water enrichment in BW. Samples were reacted with NaOH and U-(13) C3 -acetone in an autosampler vial to promote deuterium exchange with U-(13) C3 -acetone hydrogens. Headspace injections were made of U-(13) C3 -acetone-saturated air onto a 30-m DB-1MS column in electron impact-mode. Subjects ingested 30 ml (2) H2 O, and plasma samples were collected. BW was determined by standard equation. Dual-energy X-ray absorptiometry scans were performed to calculate body mass, body volume and bone mineral content. A four-compartmental model was used to estimate body composition (fat and fat free mass). Full-scan experiments generated an m/z 45 peak and to a lesser extent an m/z 61 peak. Product fragment ions further monitored included 45 and 46 using selected ion monitoring (Method1), the 61 > 45 and 62 > 46 transition using multiple reaction monitoring (MRM; Method2) and the neutral loss, 62 > 45, transition (Method3). MRM methods were optimized for collision energy (CE) and collision-induced dissociation (CID) argon gas pressure with 6 eV CE and 1.5 mTorr CID gas being optimal. Method2 was used for final determination of (2) H2 O enrichment of subjects because of lower natural background. We have developed a sensitive method to determine (2) H2 O enrichment in BW to enable measurement of FM and FFM.

Quasi-classical trajectory study of collision energy effect on the stereodynamics of H + BrO → O + HBr reaction**Project supported by the Science Fund from Jilin University, China (Grant No. 419080106440), the Chinese National Fusion Project for ITER (Grant No. 2010GB104003), and the National Natural Science Foundation of China (Grant No. 10974069).

Quasi-classical trajectory (QCT) studies on the stereodynamics of H + BrO → O + HBr reaction have been performed on the X1A' state of ab initio potential energy surface by Peterson [Peterson K A 2000 J. Chem. Phys. 113 4598] in a collision energy range from 0 kcal/mol to 6 kcal/mol. Two of the polarization-dependent generalized differential cross sections (PDDCSs), (2π/σ)(dσ00/dωt) (PDDCS00) and (2π/σ)(dσ20/dωt) (PDDCS20) are considered. The rotational polarizations of these products show sensitive behaviors to the calculated collision energy range. Furthermore, in order to gain more knowledge about vector correlations, the product angular distribution, P(θr), and the dihedral angle, P(ϕr), are calculated, and the results indicate that both the rotational alignment and orientation of the product are enhanced as collision energy increases.

The Effects of Collision Energy and Isotope on Stereodynamics for the Reactions $O^++H_2/D_2/T_2$

The Effects of Collision Energy and Isotope on Stereodynamics for the Reactions $O^++H_2/D_2/T_2$

109 砥石の鋼板貫通に及ぼす衝突エネルギーの影響

109 砥石の鋼板貫通に及ぼす衝突エネルギーの影響

Multi-drug and metabolite quantification in postmortem blood by liquid chromatography-high-resolution mass spectrometry: comparison with nominal mass technology.

High-resolution mass spectrometry (HRMS) is being applied in postmortem drug screening as an alternative to nominal mass spectrometry, and additional evaluation in quantitative casework is needed. We report quantitative analysis of benzoylecgonine, citalopram, cocaethylene, cocaine, codeine, dextromethorphan, dihydrocodeine, diphenhydramine, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine, hydrocodone, hydromorphone, meperidine, methadone, morphine, oxycodone and oxymorphone in postmortem blood by ultra-performance liquid chromatography (UPLC)-MS(E)/time-of-flight (TOF). The method employs analyte-matched deuterated internal standardization and MS(E) acquisition of precursor and product ions at low (6 eV) and ramped (10-40 eV) collision energies, respectively. Quantification was performed using precursor ion data obtained with a mass extraction window of ± 5 ppm. Fragment and residual precursor ion acquisitions at ramped collision energies were evaluated as additional analyte identifiers. Extraction recovery of >60% and matrix effect of <20% were determined for all analytes and internal standards. Defined limits of detection (10 ng/mL) and quantification (25 ng/mL) were validated along with a linearity analytical range of 25-3,000 ng/mL (R(2) > 0.99) for all analytes. Parallel UPLC-MS(E)/TOF and UPLC-MS/MS analysis showed comparable precision and bias along with concordance of 253 positive (y = 1.002x + 1.523; R(2) = 0.993) and 2,269 negative analyte findings in 159 postmortem cases. Analytical performance and correlation studies demonstrate accurate quantification by UPLC-MS(E)/TOF and extended application of HRMS in postmortem casework.

Correction of precursor and product ion relative abundances in order to standardize CID spectra and improve Ecom50 accuracy for non-targeted metabolomics

Quantitative biases in the abundance of precursor and product ions due to mass discrimination in RF-only ion guides results in inaccurate collision induced dissociation (CID) spectra. We evaluated the effects of collision cell RF voltage and collision energy on CID spectra using ten singly protonated compounds (46-854 Da) in an orthogonal acceleration time-of-flight mass spectrometer. The relative ion transfer efficiency, i.e. the relative amount of ions transferred through the ion guide at any particular RF voltage was shown to be dependent on the ion's m/z. We developed an algorithm to correct for the mass discriminating effects of RF voltage on CID spectra. The algorithm was tested for both precursor and product ions at multiple RF voltages and collision energies in order to ensure reliability. Our results suggest that compounds that generate major product ions with m/z values <150 have peak intensities that deviate substantially from their actual abundance. This has implications for small molecule metabolomics research, particularly for studies that rely on CID spectra matching methods for structure identification.

Experimental studies of H13CO+ recombining with electrons at energies between 2-50,000 meV.

An investigation into the dissociative recombination process for H(13)CO(+) using merged ion-electron beam methods has been performed at the heavy ion storage ring CRYRING, Stockholm, Sweden. We have measured the branching fractions of the different product channels at ∼ 0 eV collision energy to be the following: CO + H 87 ± 2%, OH + C 9 ± 2%, and O + CH 4 ± 2%. The formation of electronically excited CO in the dominant reaction channel has also been studied, and we report the following tentative branching fractions for the different CO product electronic states: CO(X (1)Σ(+)) + H, 54 ± 10%; CO(a (3)Π) + H, 23 ± 4%; and CO(a' (3)Σ(+)) + H, 23 ± 4%. The absolute cross section between ∼ 2-50 000 meV was measured and showed resonance structures between 3 and 15 eV. The cross section was fitted in the energy range relevant to astrophysics, i.e., between 1 and 300 meV, and was found to follow the expression σ = 1.3 ± 0.3 × 10(-16) E(-1.29 ± 0.05) cm(2) and the corresponding thermal rate constant was determined to be k(T) = 2.0 ± 0.4 × 10(-7)(T/300)(-0.79 ± 0.05) cm(3) s(-1). Radioastronomical observations with the IRAM 30 m telescope of HCO(+) toward the Red Rectangle yielded an upper column density limit of 4 × 10(11) cm(-2) of HCO(+) at the 1σ level in that object, indicating that previous claims that the dissociative recombination of HCO(+) plays an important role in the production of excited CO molecules emitting the observed Cameron bands in that object are not supported.

Effects of collision energy on stereodynamics of N(2D) + D2(X1Σg+) → ND(X3Σ−) + D(2S) reaction

The stereodynamics of N(2D)+D2(X1Σg+)→ND(X3Σ−)+D(2S) reaction has been analyzed using quasi-classical trajectory calculations with new potential energy surface (Yang et al., 2013). In the present research, four generalized polarization-dependent differential cross-sections [(2π/σ)(dσ00/dωt), (2π/σ)(dσ20/dωt), (2π/σ)(dσ22+/dωt), and (2π/σ)(dσ21−/dωt)] and distributions P(θr) and P(ϕr) were calculated. Effects of collision energy on the cross-sections and distributions were analyzed. Results show that the collision energy markedly influences the alignment effect of rotational angular momentum j′ of the product ND, but insignificantly affects the orientation effect. The tendency of forward scattering is enhanced, and backward scattering decreases with increasing collision energy.

Influence of Surface Symmetry on the Onset of Nitrogen Eley–Rideal Recombination on Tungsten

Classical trajectory simulations, using potential energy surfaces of ab initio quality, are performed to investigate the influence of crystal symmetry on the Eley–Rideal abstraction dynamics of N atoms colliding, under normal incidence, N-preadsorbed tungsten (100) and (110) surfaces. Low-energy reactivity (<0.5 eV collision energy) results much higher for the (110) crystallographic plane. Such a feature stems from the topology of the interactions upon approach of the N-gas atom toward the N adsorbate: the strong lateral corrugation responsible for a significant threshold for recombination on the (100) surface is much smoother on the (110) plane, allowing low-energy incident atoms to react. Temperature is found to only slightly affect reactivity.

A revisit of high collision energy effects on collision-induced dissociation spectra using matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry (MALDI-LIFT-TOF/TOF): application to the sequencing of RNA/DNA chimeras.

High-energy collision-induced dissociation (CID) spectra of isomeric RNA/DNA chimeras using matrix-assisted laser desorption/ionization time-of-flight LIFT mass spectrometry (MALDI-LIFT-TOF/TOF) can potentially be applied for an exhaustive fragment characterization in a nucleic acid sequencing scheme. These chimeras contain deoxynucleotides and at the 3'-end a ribonucleotide with a 3'-phosphate group. Deprotonated RNA/DNA chimeras of 4-, 5-, 7- and 10-mers are analyzed by CID. This enhances consecutive dissociations from both the precursor and prompt product anions generated by MALDI and metastable fragmentations prior to entering the LIFT cell. Gas-phase fragmentations of 4- and 5-mers produced many fragment ions, from base release prior to consecutive cleavage of the nucleotide phosphate bond linkage phosphate. The unusual a4(-) product ion is a specific and diagnostic dissociation of the 4-mer if the ribonucleotide contains cytosine. As the size of RNA/DNA chimeras increase, several abundant product ions are generated mainly from zwitterionic forms (deprotonated phosphate ester and protonated base sites): [(M-H)-BiH](-), [ai-BiH](-), wj(-), [wj, (ai-BiH)](-) (if Bi ≠ T) as internal product ion, and more rarely [wj-BiH](-). The absence of the majority of the [ai-BiH](-) series although the wj (-) series suggested that the higher critical energy processes with a loose transition state are favored yielding the wj(-) series. A large number of abundant fragment ions are detected which enable each isomer to be sequenced. This sequencing method is high-throughput, accurate and could be used to sequence isomers of up to 10-mers and also oligonucleotides of unknown sequence. However, RNA/DNA chimeras without thymine must be sufficiently concentrated to reach desorption of deprotonated molecular species to be selected in LIFT to produce all fragment ions within measurable abundances.

STATE-TO-STATE QUANTUM WAVE PACKET DYNAMICS OF THE LiH + H REACTION ON TWO AB INITIO POTENTIAL ENERGY SURFACES

The dynamics and kinetics of the LiH + H reaction have been studied by using an accurate quantum reactive time-dependent wave packet method on the ab initio ground electronic state potential energy surfaces (PES) developed earlier. Reaction probabilities for the two possible reaction channels, the LiH?+?H? H2?+?Li depletion process and the LiH + H?H + LiH hydrogen exchange reaction, have been calculated from 1?meV up to 1.0?eV collision energies for total angular momenta J from 0 to 80. State-to-state and total integral cross sections for the LiH-depletion and H-exchange channels of the reaction have been calculated over this collision energy range. It is found that the LiH-depletion channel is dominant in the whole range of collision energies for both PESs. Accurate total rate coefficients have been calculated on both surfaces from 100?K to 2000?K and are significantly larger than previous empirical estimates and previous J-shifting results. In addition, the present accurate calculations present noticeable differences with previous calculations using the centrifugal sudden approximation.

Trajectory surface hopping study of the O((3)P) + C2H2 reaction dynamics: effect of collision energy on the extent of intersystem crossing.

Intersystem crossing (ISC) dynamics plays an important role in determining the product branching in the O((3)P) + C2H2 reaction despite the necessarily small spin-orbit coupling constant values. In this study we investigate the effect of collision energy on the extent of the contribution of a spin non-conserving route through ISC dynamics to the product distributions at the initial collision energies 8.2, 9.5, and 13.1 kcal/mol. A direct dynamics trajectory surface hopping method is employed with potential energy surfaces generated at the unrestricted B3LYP/6-31G(d,p) level of theory to perform nonadiabatic dynamics. To make our calculation simpler, nonadibatic transitions were only considered at the triplet-singlet intersections. At the crossing points, Landau-Zener transition probabilities were calculated using spin-orbit coupling constant values computed at the same geometry. The Landau-Zener model for the title reaction is validated against a more rigorous Tully's fewest switches method and found to be working reasonably well as expected because of weak spin-orbit coupling. We have compared our results with the recent crossed molecular beam experiments and observed a very good agreement with respect to the primary product branching ratios. Our calculation revealed that there is no noticeable effect of the initial collision energy on the overall product distributions that corroborates the recent experimental findings. Our calculation indicates, however, that the extent of intersystem crossing contributions varies significantly with collision energy, needed to be verified, experimentally.

State-to-state resolved differential cross sections for rotationally inelastic scattering of ND3with He

State-to-state differential cross sections are reported for rotationally inelastic scattering of fully state-selected ND3 (j(k)(±) = 1(1)(-)) with He. Experimental measurements are compared with full close-coupling quantum-mechanical scattering calculations that used an ab initio potential energy surface. Results are presented for final states up to j'(k')(±) = 7(7)(-) at a mean collision energy of 430 cm(-1). For selected final quantum states, the effect of collision energy on the differential cross sections is also explored in the range 230-720 cm(-1). For the experimental studies, a hexapole electrostatic lens was used for the j(k)(±) state-selection of ND3 molecules in their electronic and vibrational ground states in a molecular beam. This state-selected molecular beam was then crossed with a beam of He atoms. The velocities of inelastically scattered ND3 molecules in single j'(k')(±) states were obtained by velocity map imaging, and converted to differential cross sections in the centre-of-mass frame by density-to-flux transformation. The close-coupling calculations reproduce well the measured angular distributions. For small changes in the rotational angular momentum quantum number (j), the ND3 is predominantly forward scattered, but the scattering shifts to the sideways and backward directions as Δj increases. For scattering into a given j'(k')(±) state, cross-sections for collisions that conserve the ± symmetry associated with the ND3 inversion vibration are larger and generally more forward scattered than the corresponding symmetry-changing processes.

Collision energy effect on stereodynamics for Sr+CH3I→SrI+CH3

Based on semiemperical London-Eyring-Polanyi-Sato (LEPS) potential energy surface (PES), stereodynamic properties of the reaction Sr+CH3I→SrI+CH3 in different initial reagent collision energies are studied theoretically by using the quasiclassical trajectory method. The results indicate that the collision energy of reagent has considerable influences on the orientations and alignments of angular momentum of products for the title reaction.

Trajectory-based nonadiabatic molecular dynamics without calculating nonadiabatic coupling in the avoided crossing case: trans↔cis photoisomerization in azobenzene.

We develop a novel method to simulate analytical nonadiabatic switching probability based on effective coupling and effective collision energy by using only electronic adiabatic potential energy surfaces and its gradients in the case of avoided crossing types of nonadiabatic transitions. In addition, the present method can keep the same time step for computing both on-the-fly trajectory and nonadiabatic transitions accurately. The present method is most useful for localized nonadiabatic transitions induced by conical intersection. We employ the on-the-fly surface hopping algorithm with an ab initio quantum chemistry calculation to demonstrate a dynamic simulation for photoisomerization in azobenzene. Simulated quantum yield and lifetime converge to 0.39 and 53 femtosecond, respectively (0.33 and 0.81 picosecond) for cis-to-trans (trans-to-cis) photoisomerization with up to 800 (600) sampling trajectories. The present results agree well with those of the experiment, as well as results simulated with use of nonadiabatic coupling within Tully's fewest switching method. The present trajectory-based nonadiabatic molecular dynamics free from nonadiabatic coupling greatly enhances the simulation power of molecular dynamics for large complex chemical systems.

Effects of the collision energy on the stereodynamics of the reaction: S(3P) + H2 (v = 0, j = 0) → SH + H

Quasi-classical trajectory calculations are firstly employed to study the stereodynamics of the title reaction on the lowest triplet state (3A″) potential energy surface constructed by Lv et al. (2012) [10]. The calculated reaction probabilities and cross sections are in good agreement with the previous quantum mechanics results. The effects of collision energy on the vector properties including the k–k′ distribution and product polarization are investigated for the v=0 and j=0 states of H2 at Ecol=1.2, 1.4, 1.8 and 2.2eV. The calculated results indicate that the collision energy plays an important role in the stereodynamics of the title reaction.

Quantum Dynamical Study of the He + NeH+ Reaction on a New Analytical Potential Energy Surface

An analytical potential energy surface (PES) for the ground state of the [HeHNe](+) system has been constructed from a set of 19,605 ab initio data points, obtained from coupled cluster singles and doubles with perturbative triples correction calculations and the aug-cc-pVQZ basis set. The PES is based on the many-body expansion form proposed by Aguado and Paniagua (J. Chem. Phys. 1992, 96, 1265), and it has a root-mean-square error of 0.03 kcal/mol. The minimum energy pathways (MEPs) for different Ne-H-He angles are calculated, and it is found that the MEP for 180° (linear) goes through the deepest potential energy well. Preliminary quantum dynamical studies are performed for the He + NeH(+) (v = 0-2, j = 0-3) → HeH(+) + Ne reaction in the 0.0-0.5 eV collision energy range. Quantum calculations are carried out using a time-dependent wave packet method within the centrifugal sudden approximation. Reaction probabilities exhibit strong oscillatory behavior arising because of the metastable [HeHNe](+). Vibrational excitation has been found to enhance the reaction cross sections.

Electrospray Ionization Mass Spectral Characteristics and Fragmentation Mechanisms of Tanshinones in &lt;i&gt;Radix Salvia miltiorrhiza&lt;/i&gt;

Cryptotanshinone, tanshinone I, and tanshinone IIA were analyzed by High-performance liquid chromatography /electrospray ionization-mass spectrometry. MSn spectra were obtained and optimized by energy collision induced dissociation (CID) from [M+H]+ ions, the effect of collision energy on production of fragmental ions were studied and optimal signals were achieved. With the collision energy of 35%, tanshinones have optimal signals of fragmental ions and maximal amounts of product fragment ions respectively. The fragmentation pathways for the compounds were studied, and this information would be helpful for the quantitative and pharmacokinetic analysis of tanshinones.

Drug Screening in Medical Examiner Casework by High-Resolution Mass Spectrometry (UPLC-MSE-TOF)

Postmortem drug findings yield important analytical evidence in medical examiner casework, and chromatography coupled with nominal mass spectrometry (MS) serves as the predominant general unknown screening approach. We report screening by ultra performance liquid chromatography (UPLC) coupled with hybrid quadrupole time-of-flight mass spectrometer (MS(E)-TOF), with comparison to previously validated nominal mass UPLC-MS and UPLC-MS-MS methods. UPLC-MS(E)-TOF screening for over 950 toxicologically relevant drugs and metabolites was performed in a full-spectrum (m/z 50-1,000) mode using an MS(E) acquisition of both molecular and fragment ion data at low (6 eV) and ramped (10-40 eV) collision energies. Mass error averaged 1.27 ppm for a large panel of reference drugs and metabolites. The limit of detection by UPLC-MS(E)-TOF ranges from 0.5 to 100 ng/mL and compares closely with UPLC-MS-MS. The influence of column recovery and matrix effect on the limit of detection was demonstrated with ion suppression by matrix components correlating closely with early and late eluting reference analytes. Drug and metabolite findings by UPLC-MS(E)-TOF were compared with UPLC-MS and UPLC-MS-MS analyses of postmortem blood in 300 medical examiner cases. Positive findings by all methods totaled 1,528, with a detection rate of 57% by UPLC-MS, 72% by UPLC-MS-MS and 80% by combined UPLC-MS and UPLC-MS-MS screening. Compared with nominal mass screening methods, UPLC-MS(E)-TOF screening resulted in a 99% detection rate and, in addition, offered the potential for the detection of nontargeted analytes via high-resolution acquisition of molecular and fragment ion data.

The effect of collision energy on the stereodynamics of the reaction H(2S) + NH (X3 Σ−, v = 0, j = 0) → N(4S) + H2

The quasi-classical trajectory (QCT) is calculated to study the stereodynamics properties of the title reaction H(2S) + NH(X3 Σ−) → N(4S) + H2 on the ground state 4A″ potential energy surface (PES) constructed by Zhai and Han [2011 J. Chem. Phys. 135 104314]. The calculated QCT reaction probabilities and cross sections are in good agreement with the previous theoretical results. The effects of the collision energy on the k—k′ distribution and the product polarization of H2 are studied in detail. It is found that the scattering direction of the product is strongly dependent on the collision energy. With the increase in the collision energy, the scattering directions of the products change from backward scattering to forward scattering. The distribution of P(θr) is strongly dependent on the collision energy below the lower collision energy (about 11.53 kcal/mol). In addition, the P(φr) distribution dramatically changes as the collision energy increases. The calculated QCT results indicate that the collision energy plays an important role in determining the stereodynamics of the title reaction.