Internal Energy Effects Research Articles

Internal energy effects on charge stripping spectra of [C 7H 8] [rad]+ and [C 5H 6] [rad]+ radical cations

MS/MS/MS experiments were carried out using a large-scale tandem mass spectrometer featuring a sector-quadrupole-sector geometry to probe the C 7 H 8 + and C 5 H 6 + radical cations. These ions ( m/ z 92 and 66) were produced from metastable ionized precursors or charge exchange reactions in the quadrupole cell; subsequent fragmentations and double ionization were performed after mass-selection and collisional activation with oxygen. Charge stripping spectra show significant variations in the relative intensities of the same doubly charged species generated in different ways. These variations are likely to be associated with the inherent differences in internal energy content.

The entropy based contribution to bulk modulus: A thermodynamic analysis

It is suggested that bulk modulus at any finite temperature can be split into two fundamental contributions, viz., the one arising from internal energy or enthalpy effects and the rest from the effect of entropy. A rigorous thermodynamic analysis of the latter quantity, namely the entropy-based contribution to bulk modulus is presented in this study. In particular, it is shown that this contribution governs the intrinsic or pure thermal sensitivity of bulk modulus and can be negative, positive or even zero depending upon the relative magnitudes of the pressure derivative of bulk modulus and the isothermal Anderson–Grüneisen parameter. It is also identified that this entropy-based contribution is related to the thermal pressure, and hence is expected to play a significant role in deciding the overall temperature sensitivity of bulk modulus at high temperature. A few simple approximations are suggested for estimating this quantity in terms of readily available thermal property data. In addition, an illustrative calculation is presented for MgO.

Thermodynamically consistent relations involving plasticity, internal energy and thermal effects

Experimental data associated with plastic deformations indicate that the temperature is less than that predicted from dissipation based on plastic work. To obtain reasonable correlation between theoretical and experimental results, the plastic work is often multiplied by a constant beta. This paper provides an alternative thermodynamic framework in which it is proposed that there is an additional internal energy associated with dislocation pile-up or increase in dislocation density. The form of this internal energy follows from experimental data that relates flow stress to dislocation density and to equivalent plastic strain. The result is that beta is not a constant but a derived function. Representative results for beta and temperature as functions of effective plastic strain are provided for both an uncoupled and a coupled thermoplastic theory. In addition to providing features that are believed to be representative of many metals, the formulation can be used as a basis for more advanced theories such as those needed for large deformations and general forms of internal energy.

Collisions of slow polyatomic ions with surfaces: the scattering method and results

Surface-induced dissociation (SID) and reactions following impact of well-defined ion beams of polyatomic cations C 2H 5OH +, CH 4 +, and CH 5 + (and its deuterated variants) at several incident angles and energies with self-assembled monolayers (SAM), carbon surfaces, and hydrocarbon covered stainless steel were investigated by the scattering method. Energy transfer and partitioning of the incident projectile energy into internal excitation of the projectile, translational energy of products, and energy transferred into the surface were deduced from the mass spectra and the translational energy and angular distributions of the product ions. Conversion of ion impact energy into internal energy of the recoiling ions peaked at about 17% of the incident energy for the perfluoro-hydrocarbon SAM, and at about 6% for the other surfaces investigated. Ion survival probability is about 30–50 times higher for closed-shell ions than for open-shell radical cations (e.g., 12% for CD 5 + versus 0.3% for CD 4 +, at the incident angle of 60° with respect to the surface normal). Contour velocity plots for inelastic scattering of CD 5 + from hydrocarbon-coated and hydrocarbon-free highly oriented pyrolytic graphite (HOPG) surfaces gave effective masses of the surface involved in the scattering event, approximately matching that of an ethyl group (or two methyl groups) and four to five carbon atoms, respectively. Internal energy effects in impacting ions on SID were investigated by comparing collision energy resolved mass spectra (CERMS) of methane ions generated in a low pressure Nier-type electron impact source versus those generated in a Colutron source in which ions undergo many collisions prior to extraction and are essentially vibrationally relaxed. This comparison supports the hypothesis that internal energy of incident projectile ions is fully available to drive their dissociation following surface impact.

Internal energy effects in the reactivity of CO 22+ doubly charged molecular ions with CO 2 and CO

Reactivity of the dication CO 2 2+ in dependence on its internal energy was studied in collision with CO 2 and CO. The dication was obtained by photoionization of the CO 2 molecule by synchrotron radiation and the guided beam apparatus CERISES was used in these studies. Spontaneous dissociation of CO 2 2+ to CO + and O + was observed without any target gas in the reaction cell. With CO 2 or CO as a target gas, CO + and O + fragment ions were formed as products of dissociative charge transfer, while the contribution of collision-induced dissociation of the reactant CO 2 2+ to their formation was found negligible. The CO + yield showed a considerable dependence on the internal energy of the reactant dication CO 2 2+: the branching ratio CO +/O + increased gradually with photon energy between 38.7 and 39.4 eV. We interpret this observation as being due to the increase in the instantaneous distances at the extrema of vibrational motion of the dication with increasing internal energy. This modifies the Franck-Condon factors in the charge transfer process and leads to a preferential population of the vibrationally excited states of the product cation CO 2 +(C) known to lead exclusively to the dissociation products CO ++O. An indirect mechanism that requires the coupling of the first excited (a) state of the dication with the higher vibrational states of the CO 2 2+ (X) state is proposed to explain the threshold behaviour observed in our results.

Successive reactions of iron carbonyl cations with methanol

The reactivity of Fe(CO) n + cations with methanol has been investigated using a triple-cell Fourier transform ion cyclotron resonance apparatus. Successive substitutions of the CO ligands by methanol occur rapidly with similar rates. For n = 3–5 the last CO ligand is not replaced, and the terminal substitution products are FeCO(CH 3OH) n−1 +. A second reaction pathway is observed for n = 3–5, in which two CO ligands are replaced by one methanol molecule. This pathway occurs even if the Fe(CO) n + ions have been radiatively relaxed before reaction, providing information on the bond energies in the product ions. Strong internal energy effects are observed on the reaction rates and branching ratios for further substitution of the intermediate products. The substitution product Fe(CH 3OH) + from FeCO + reacts further, with C–O bond cleavage followed by substitution. The resulting Fe[C 2, H 7, O 2] + ion undergoes either isomerization or collisional deactivation, then slow association with methanol. The reaction of Fe +, due to excited states only, begins with formation of FeOH + and involves the same final steps as in the preceding case.

Intermolecular energy transfer probabilities from trajectory calculations: A new approach

A new method to calculate intermolecular energy transfer probability density function P(E′,E) from trajectory calculations is proposed. The method distinguishes between effective trajectories that contribute to P(E′,E) and those with very large impact parameter which do not. The P(E′,E) thus found obeys conservation of probability and detailed balance and is independent of the impact parameter. The method is demonstrated for benzene–Ar collisions at various temperatures and internal energies. With this method it is possible to combine ab initio inter and intramolecular potentials with trajectory calculations, obtain P(E′,E) and use that in master equation calculations to obtain rate coefficients and populations distributions without resorting to any a priori assumptions and energy transfer models. In addition, the effects of internal energy, temperature and rotations on the average energy transferred are discussed. Global potentials in center-of-mass and minimal distance coordinates which are obtained by averaging 20 000 and 50 000 trajectories are reported. It is shown that Lennard-Jones or ab initio pairwise potentials yield a Buckingham-type global potentials.

Total cross sections for low energy collisions of H3+ with molecular hydrogen and rare gases

Measurements of total cross sections for collision induced dissociation (CID) and proton abstraction have been made for the reactants H3++H2, Ar, and He. The laboratory collision energies range from a few up to 400 eV and D3+ has been substituted to investigate possible isotope effects. The CID cross sections of H3+→H++H2 or H2++H maximize at a value of a few Å2. Proton abstraction is the dominant process for relative collision energies below 5 eV and is observed to lead to a highly excited H3+ product which often autodissociates. Dissociative charge transfer at higher collision energies is responsible for producing H2+ product ions. The role of internal energy contained within the H3+ primaries in previous experiments and the effects of internal energy on the cross section measurements presented here are also discussed.

Internal Energy Effects in Mass Spectrometry

The internal energy of an ion has a very large effect on the appearance of the mass spectrum. The first part of this paper gives the theoretical background: (i) dependence of the reaction rate on internal energy; (ii) correspondence between the reaction rate and fragment ion abundances; (iii) role of the residence time of an ion in various parts of the instrument; (iv) the breakdown curve; and (v) the degrees of freedom or number of oscillators affected. In the second part internal energy distributions are discussed: those of molecular ions produced by various ionization techniques and of precursor ions in tandem mass spectrometry. The latter topic is closely connected with secondary excitation, and the particular case of collisional activation is discussed in some detail. In the final part, practical examples of internal energy effects in mass spectrometry are given, including high- and low-energy electron impact, chemical ionization using various reagent gases, metastable and collision-induced dissociation, keV and low-energy collision induced dissociation and matrix-assisted laser desorption/ionization.

Time and internal energy dependent fluorescence spectra of naphthol⋅water clusters

Time-resolved fluorescence spectra of 1-naphthol⋅(H2O)n clusters formed in a supersonic jet were measured under conditions of strong and weak cooling. Wavelength selectivity was used to excite very similar size distributions in both cases, thereby allowing controlled study of temperaturelike effects of internal energy in clusters. In both warm and cold clusters, long wavelength fluorescence from 1-naphtholate formed via an intermolecular excited state proton transfer (ESPT) reaction is observed, but this emission was significantly more red-shifted in warmer clusters. The fluorescence spectra of warmer clusters also shift strongly to the red after excitation, on a time scale of about 10 ns. Colder clusters showed no spectral shifts on this time scale. A weak solvent isotope effect was also observed. Similar clusters of 2-naphthol with water were not observed to undergo ESPT under any conditions. The time-dependent spectra indicate that ESPT in warm 1-naphthol⋅water clusters is not prompt, but continues on a ∼10 ns time scale, as does dynamic stabilization of previously reacted clusters. The ESPT rate is believed to be controlled by the rate at which the water relaxes around the naphthol, via interaction with two electronic excited states. The 10 ns and the two faster [R. Knochenmuss, G. R. Holtom, and D. Ray, Chem. Phys. Lett. 215, 188 (1993)] time scales now known in the spectral dynamics are discussed in terms of water solvation relaxation, and connected to the bulk by means of molecular dynamics simulations.

Efficiency of collision‐induced ionization of fast neutrals: Effects of neutral internal energy and neutral translational energy

AbstractThe ionization efficiencies of fast beams of CO and C2H4, with oxygen as target gas were shown to increase with increasing translational energy and to decrease with increase in internal energy. The latter may arise from a greater probability of homolysis in the neutral projectile species; it is not likely to arise from increased ionization of the target. Experimental parameters (and their validity) relating to the measurement of collision‐induced dissociative ionization mass spectra and which are also applicable to the reionization step in neutralization—reionization mass spectra were investigated.

Dynamics of ion/molecule reactions

This review is devoted to the main advances in the investigation of ion/molecule reaction dynamics since the last International Mass Spectrometry Conference. Developments of the experimental techniques to prepare the reactants in selected internal states and well-defined collision energies and to analyse the internal state, the kinetic energy and angular distribution of the products are described. Examples of kinetic and internal energy effects on reaction dynamics are presented for simple systems such as (Ar, N 2) + and (Ar, O 2) + as well as for polyatomics: Ar + + H 2O, He + + N 2O, MH + + MH and (COS, C 2H 2) +, for which state-selected or state-to-state studies have been performed. Complementarity of the various techniques is shown. Recent advances in very low temperature studies are also presented. Theoretical interpretations of the experimental results are described but no detail on the theoretical investigations is given. The need for further developments in the experimental and theoretical methods is underlined and some of the possible trends are mentioned.

Internal and translational energy effects on the charge- transfer reaction of CO +2 with O 2

We have investigated the reaction of CO + 2 with 0 2 over a range of kinetic energies with a guided ion beam apparatus and over a range of temperatures and kinetic energies with a variable-temperature selected-ion flow drift tube. The rate constants decrease with increasing kinetic energy at low energy and increase at higher energy. Below about 10 eV, reaction proceeds by charge transfer only. Above 10eV, O + and CO + product ions are observed in addition to the charge-transfer channel. At low energy, i.e. below 0.1eV, the rate constants at a particular center-of-mass kinetic energy, 〈KE cm〉, do not depend on the temperature of the buffer gas. This indicates that energy in rotations and in the bending vibrational modes does not play a major role in determining reactivity. Above 0.1 eV, the rate constants at a particular 〈KE cm〉 do depend on temperature, such that the higher the buffer gas temperature the larger the rate constants. Analysis of the data suggests that the enhancement observed with temperature is primarily due to excitation of the CO + 2 stretching vibrational modes. The analysis indicates that excitation of the CO + 2 stretching modes increases the rate constant by approximately an order of magnitude. Excitation of bending vibrations may also enhance the efficiency of charge transfer above 0.2 eV. Translational energy causes a small increase in the charge-transfer rate constant above 0.3 eV.

Translational and internal energy effects in reactions of O + and O +2 with SiF 4

Guided ion beam techniques are used to measure the cross sections as a function of kinetic energy for reaction of SiF 4 with O +( 4S) and O + 2 ( 2Π g, ν = O). Reactions of excited O + 2 ions are also examined and are found to react more efficiently than ground state ions. The major reactions are dissociative charge transfer processes, although O + also reacts to form OF + SiF + 3 efficiently and O + 2 reacts to form minor amounts of SiOF + x ( x = 1−3).

Characterization of the Rotation of Cometary Nuclei

Abstract.I review the primary methods used to determine the spin state of cometary nuclei and the pitfalls and successes experienced in their use. There are in excess of 60 reported determinations of rotational periodicities, but only a few (~4) appear to be reliable, and even these do not necessarily fully describe the true rotational state. An adequate rotational ephemeris is not, at present, available for a single cometary nucleus.Because recent studies indicate that active cometary nuclei could be in excited spin states, I also review the theory of rigid body rotation from the point of view of remote (astronomical) observers, covering what is known of the effects of nutation on lightcurves, the influence of torques induced by jet activity, and the effects of internal energy and mass dissipation, and nuclear splitting.The available knowledge on rotation for 8 comets, including P/Halley, is reviewed. Outstanding questions that need early resolution are: (1) Can a consensus be achieved on the rotational state of P/Halley? (2) Is it possible to accurately determine the amplitude of the transverse non-gravitational force associated with rotation? (3) Are the orientations of fan-like comas a valid indicator of the orientation of the spin vector – can definitive observational checks be made in a few cases?Improved observational and interpretational techniques are needed to advance this field. Improved time-series and zero-date analyses are needed to connect existing and future data sets and to search for multiple periodicities in cometary lightcurves; improved sampling and extension of time-series observations with moderate- and large-aperture telescopes at good sites is needed; near-simultaneous photometric and radiometric observations made when cometary activity is low are particularly significant; well-sampled time-series imaging of near-nuclear phenomena (together with adequate software to analyze them) is essential to diagnose rotational states if nutation is present.

A Theoretical Analysis of the Unimolecular Decomposition of Ethanol: Internal Energy Effects and Pressure Dependence

A Theoretical Analysis of the Unimolecular Decomposition of Ethanol: Internal Energy Effects and Pressure Dependence

Internal energy effects in the collision‐induced dissociation of large biopolymer molecular ions produced by electrospray ionization tandem mass spectrometry of cytochrome c

AbstractThe effects of internal energy upon metastable and collision‐induced dissociation (CID) processes observed in the tandem mass spectrometry of multiply protonated molecules of horse‐heart cytochrome c (Mr 12360) are described. The internal energy of the multiply protonated (15H+) molecules (at m/z 825) formed by electrospray ionization (ESI) was manipulated using electric fields in the atmospheric pressure/vacuum interface region. Highly efficient CID is obtained for molecular ions collisionally activated in the ESI interface. The dissociation efficiency at 3.8 eV to 5.8 eV (center of mass) collision energies for internally “hot” molecular ions under multiple collision conditions in a triple quadrupole mass spectrometer is shown to be much greater than for “cold” ions. The CID spectra show dramatic effects due to internal energy, with charge stripping dominating for cold ions (where CID efficiency is very low) and extensive fragmentation observed for hot ions.

Internal energy effects on ion-neutral complexes from unimolecular dissociation of n-propyl phenyl ether radical cations

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTInternal energy effects on ion-neutral complexes from unimolecular dissociation of n-propyl phenyl ether radical cationsEric L. Chronister and Thomas Hellman MortonCite this: J. Am. Chem. Soc. 1990, 112, 1, 133–139Publication Date (Print):January 1, 1990Publication History Published online1 May 2002Published inissue 1 January 1990https://doi.org/10.1021/ja00157a021RIGHTS & PERMISSIONSArticle Views83Altmetric-Citations49LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (989 KB) Get e-Alerts Get e-Alerts

Internal energy effects on mass spectrometric fragmentation

Etudes experimentale et theorique de l'effet de l'energie thermique vibrationnelle-rotationnelle interne sur la dissociation induite par electron observee dans des spectres de masse

Internal energy effects in photodissociation: relaxation of excited thiophenol ions formed by electron-impact ionization

The internal energy of thiophenol ions formed by moderate energy electron-impact ionization was measured as a function of the time after ionization using a visible laser probe. Immediately after ionization, it was found that about 60% of the ions had internal energies greater than 0.8 eV. At collisionless pressures, the ions were found to relax below 0.8 eV at a rate of 3 s −1. At higher pressure, where the collision rate is approximately 1 s −1, the relaxation rate was measured at 4.5 s −1. The results are compared with the energy deposition function inferred from the PES spectrum, and it is suggested that electron impact at 17 eV gives a somewhat smaller fraction of ions above 0.8 eV than does photoionization at 21 eV.