Ion Cyclotron Resonance Spectrometer Research Articles

Ion cyclotron resonance spectrometry - a review

INTRODUCTION This review covers the period from 1980, when a review on ICR instrumentat ion and theory by the same author appeared { I } , u n t i l ear ly 1984. A comprehensive account is given of the fo l lowing topics: p r inc ip le of the method, ion motion and detect ion, instrumentat ion, unimolecular processes and photon in te rac t ion , some fundamental aspects of ion-molecule react ions: theory, thermochemistry, equ i l ib r ium studies and reactions involv ing metal ions, ana ly t ica l appl icat ions. Several review a r t i c les and books dealing with more general topics related to the f i e l d have appeared in the past years {2-12} which also contain ICR mater ia l . A two volume book on gas phase ion chemistry, edited by Bowers {2} , contains among others several chapters dealing with ICR spectrometry, on the s t a b i l i t y of gas phase ions from equ i l ib r ium gas phase bas ic i ty measurements by Aue and Bowers, on electron a f f i n i t i e s by Janousek and Brauman, on the gas phase ac id i t y scale by Bartmess and Mclver, and on ion d issoc ia t ion by Dunbar. There are two books on Fourier transform and related techniques { 3,4 } containing material on FT ICR (Fourier transform ion cyclotron resonance) spectromet r y . The Spec ia l is t Periodical Report on Mass Spectrometry { 5 } also covers ICR spectrometry. Spectroscopy, chemistry and structure of ions in the gas phase are discussed in two recent books {6 ,7 } . FT ICR spectrometers can be operated in a mass mode and are therefore included in the recent volume on tandem mass spectrometry { 8 } . Two papers by Morton deal with neutral products from cation-molecule reactions in the gas phase { 10 } and gas phase analogues of so lvo lys is reactions { 11 } . F ina l l y a paper on bimolecular react ions of nucleophiles in the gas phase {12} , which discusses mass spectromet r i c methods suited fo r study of such react ions, should be mentioned. In 1982 a progress report on ICR spectrometry covering the whole f i e l d was published

The heats of formation of some protonated olefinic carbonyl compounds: [C5H9O]+ and [C4H7O2]+ ions

AbstractThe proton transfer equilibrium reactions involving 3‐penten‐2‐one, 3‐methyl‐3‐buten‐2‐one, crotonic acid and methacrylic acid were carried out in an ion cyclotron resonance (ICR) spectrometer. The semiempirical method MNDO, used to estimate the heats of formation for 14 protonated [C5H9O]+ and [C4H7O2]+ ions and the energetic aspect of the fragmentations of metastable [C6H12O]+. and [C6H12O2]+. ions, leads to the conclusion that the ions corresponding to protonation at the carbonyl oxygen are the most stable. Thus the experimentally determined heats of formation of protonated olefinic carbonyl compounds can be attributed to the following structures: [CH3COHCHCHCH3]+ (δHf = 490 KJ mol−1), [CH3COHC(CH3)CH2]+ (δHf = 502 KJ mol−1), [HOCOHCHCHCH3]+ (δHf = 330 KJ mol−1) and [HOCOHC(CH3)CH2]+ (δHf = 336 KJ mol−1).

Array-processor-based Fourier-transform ion cyclotron resonance mass spectrometer

A Fourier-transform ion cyclotron resonance spectrometer (Fourier-transform mass spectrometer) is described which takes advantage of the speed and flexibility of a substantial array processor. Using this array processor, a preprogrammed instruction stack is read sequentially to generate the sequence of rf excitation waveforms applied to the transmitter plates, and the ion response signal is accumulated, processed, and transformed. Control, programming, storage, output, and display functions are handled by the host minicomputer system. Broadband capability allows data acquisition up to 3.5 MHz, giving the ability to acquire extended mass spectra in one pass. The rapid transforming capability of the processor makes it convenient to acquire frequency-domain spectra in real time.

The reaction of NH+⋅3 with H2S: Dependence on the translational and internal energy of NH+⋅3

The reactions of vibrationally and of kinetically excited NH+⋅3 ions with H2S were investigated using a tandem ion cyclotron resonance spectrometer. NH+⋅3 ions with internal energies ranging from 1–5 eV were generated by charge transfer reactions, whose energy partioning is known. The charge transfer reagents used included Ar+⋅, Kr+⋅, Xe+⋅, N2+⋅, CO+⋅2 , CO+⋅, and O+⋅2 . The ionic products formed in the reaction of excited NH+⋅3 with H2S were NH+4 , H2S+⋅ and H3S+. It is shown that the product distribution is sensitive to the NH+⋅3 internal energy. At low internal energies, NH+4 is the dominant product, while at 5 eV all three reaction products are of comparable intensity. Competition between formation of H2S+⋅ and H3S+ is effective only at NH+⋅3 internal energies above 2 eV. The total rate constant was found to be 6±2×10−10 cm3/s and appeared to be independent of the internal energy of NH+⋅3 . Kinetically excited NH+⋅3 ions were formed using ICR double resonance and the effect on product distribution and total rate constant in the reaction with H2S was studied. It is shown that kinetic energy exclusively drives the charge transfer channel. The total rate was independent of the NH+⋅3 kinetic energy in the energy range of the experiment.

Radiation-induced ionization and excitation in liquid p-dioxane

The fluorescence of neat liquid p-dioxane and p-dioxane-water mixtures has been studied as a function of wavelength in the range 200–110 nm, and in the system under beta irradiation. It is seen that the quantum yield of fluorescence declines from the absorption threshold to the ionization onset (∼ 160–170 nm), because of the increasing importance of the competing decomposition processes. Above the ionization onset, there is a slight increase in the quantum yield of fluorescence as a result of the occurrence of “recombination fluorescence”. However, it is estimated that in this region, neutralization does not always lead to a vibrationally equilibrated excited state. This explains in part why the G-value of thermally equilibrated S 1 states is considerably lower than G(ion)(∼5), under conditions that fluorescence originates mainly from charge recombination. Auxiliary experiments carried out in the gas phase, in an ion cyclotron resonance spectrometer, elucidated the reaction of p-C 4H 8O 2+ ions with p-dioxane molecules. The results indicate that in the gas phase, proton transfer between these reactants is thermoneutral, and occurs with a lowered efficiency (i.e. does not occur at every collision) in contrast with m-dioxane for which the corresponding proton transfer reaction is highly exothermic and k Rn = k Collision . In the liquid phase, proton transfer is unimportant in the p-dioxane system, but probably is the predominant fate of the m-C 4H 8O 2+ ion in m-dioxane. The well known shift of emission to lower energies in p-dioxane-water mixtures has been examined; the shift depends only on the concentration of water, and not on the type or energy of the radiation. In the presence of added 1-methylnaphthalene, it is seen that there is no change in the quantum yield of emission from methylnaphthalene at energies below the ionization onset, but that there is a decrease in the fluorescence yield with increasing water concentration above the ionization threshold. In p-dioxane: H 2O: toluene mixtures, on the other hand, the toluene fluorescence diminishes with increasing water concentration at all energies. These observations are interpreted in terms of changes in the energy level of the electronically-excited p-dioxane-water aggregate and on proton transfer reactions involving dioxane-water aggregates.

Infrared Multiple Photon Photochemistry of Gas Phase Ions

AbstractAn ion cyclotron resonance (ICR) spectrometer can be used to generate, trap, and detect gas phase ions which are irradiated with an infrared laser. Infrared multiple photon (IRMP) photochemistry can be conveniently studied under these conditions. Results of several recent studies are discussed.

C 4H 5N +· ions studied by ion/molecule reactions and photodissociation

C 4H 5N +· ions, generated from five different isobaric neutral precursors, have been studied and characterized by ion molecule reactions and their behaviour upon photodissociation, using an ion cyclotron resonance (ICR) spectrometer. It is found that ions derived from methacrylonitrile and pyrrole retain the structures of their parent neutral molecules. Cyclopropyl cyanide and crotonitrile ions partly isomerize to an unreactive C 4H 5N +· ion, presumably pyrrole, to the extent of 15% and 6%, respectively. Allyl cyanide gives rise to three ionic species: the original structure (25%), crotonitrile (45%) and pyrrole (30%).

Unimolecular decomposition and vibrationally induced electron autodetachment of acetone enolate ion

Acetone enolate ion trapped in a pulsed ion cyclotron resonance spectrometer cell was irradiated with a pulsed CO2 laser. Both unimolecular decomposition to give HC2O− and CH4, and vibrationally induced electron autodetachment were observed. The data are consistent with a scheme in which a vibrationally excited enolate ion decomposes through an adiabatic (decomposition) pathway and a nonadiabatic (autodetachment) pathway. From an analysis of the branching using statistical reaction rate theory the autodetachment rate constant ka is estimated to be ∼107 s−1 at ∼1 eV above the electron detachment threshold.

Infrared-enhanced multiphoton dissociation of iodobenzene cations

When gas-phase iodobenzene cations in an ion cyclotron resonance spectrometer are irradiated simultaneously with visible 610 nm and IR 977 cm −1 photons, the visible two-photon process is enhanced by a factor of up to three. The experimental pressure and intensity dependences can be modeled using a set of rate equations for the evolution of the populations of different internal energy levels. Modeling suggests that the major mechanism for the mixed visible/IR process is the absorption of several IR photons, followed by the absorption of one visible photon which brings about dissociation: that the visible photoexcitation cross section decreases with increasing ion internal energy: that IR pumping does not compete successfully with relaxation processes near dissociation threshold: and that the IR radiative relaxation time is constant ≈ 500 ms.

Reactions of carbonyl compounds and group 1b metals in a plasma in the wake of a spark

The reaction of the model system of C 3H 6 and Cu to produce cationized species C n,H m,Cu + in the spark source mass spectrometer proceeds through neutral organic species and Cu +. On this basis reactions of Cu +, Ag + and Au + with neutral methyl, ethyl and propyl ethanoate, butanone, butanal, 2,4-pentanedione, ethanoic acid and ethanoic anhydride are compared with reactions of similar compounds with laser-generated Cu + in an ion cyclotron resonance spectrometer. In the wake of the spark more fragmentation of the cationized organic species is observed. The simple cationized molecule is not observed if the metal ion has low-lying excited states.

Pyrolysis effects on the reactions of alkoxide anions

The distribution of products in negative chemical-ionization spectra of alcohols are shown to remain unaffected (<1%) by pyrolytic reactions. On the other hand, it is shown that slow ion/molecule reactions can be obscured by fast processes implying impurities formed by pyrolysis. The importance of pumping speed in ion cyclotron resonance (ICR) spectrometers is also discussed.

Energy disposal in charge transfer reactions producing NH+.3: Dependence of the NH+.3+H2O reaction on NH+.3 internal energy

The division of available energy between translational and internal modes has been determined for seven charge transfer reactions which produce NH+.3. The charge transfer reagent ions studied were Ar+., Kr+., Xe+., N+.2, O+.2, CO+., and CO+.2. The average kinetic energy released in the reaction was measured directly using an ion cyclotron resonance (ICR) technique. The internal energy deposited in the NH+.3 product was determined by further reacting the NH+.3 product with H2O in a tandem ICR spectrometer. The product distribution of this subsequent reaction is shown to depend strongly on the NH+.3 internal energy; and this dependence is quantitatively determined. The energy deposited in the neutral charge transfer product is calculated using energy balance. Comparisons are made between charge transfer reagent ions of similar recombination energies to show the effects of reagent ion internal modes on the division of available reaction energy.

High magnetic field fourier transform ion cyclotron resonance spectroscopy

A Fourier transform ion cyclotron resonance spectrometer (FT ICR) utilizing a superconducting magnet is described. A narrow-band ultrahigh resolution and a wide-band medium resolution mode can be used. For large mass ranges also correlation spectroscopy can be applied. In the high resolution mode a resolution of m/Δm >10 8 at m/q = 18, H 2O + and of m/Δm >550,000 at m/q = 866 are obtained. Due to the high magnetic field (4.7 Tesla) trapping times of more than twelve hours have been observed. The spectrometer is equipped with a direct insertion probe. The ions are formed by electron impact or by low pressure chemical ionization directly in the cell. Masses higher than m/q = 2,000 can be measured with high resolution.

Measurement of hydrogen/deuterium ratios in ethanol/ethanol-O-d mixtures by chemical ionization mass spectrometry with tetramethylsilane as reagent gas

Chemical ionization reactions of the trimethylsilyl cation with mixtures of ethanol and ethanol-O-d have been studied in an ion cyclotron resonance spectrometer in order to explore the potential of this reagent for in situ isotope ratio measurements. The trimethylsilyl cation forms an adduct with the alcohol giving a large peak in the mass spectrum at mass P + 73. The H/D ratios measured by the presence of a novel isotope exchange reaction. This isotope exchange reaction involves the transfer of H and D between H/sub 2/O and EtOH mediated by the presence of the silyl cation. The difficulties and advantages of employing the trimethylsilyl cation as a chemical ionization reagent are discussed. If no ..beta.. hydrogens are present, the trimethylsilyl cation will be a useful reagent for determining OH/OD ratios. Scrambling occurs if ..beta.. hydrogens are present.

ChemInform Abstract: PHOTODISSOCIATION STUDY OF C6H6O+.CNTDOT. IONS IN AN ION CYCLOTRON RESONANCE SPECTROMETER

Chemischer InformationsdienstVolume 13, Issue 25 Preparative Organic Chemistry ChemInform Abstract: PHOTODISSOCIATION STUDY OF C6H6O+.CNTDOT. IONS IN AN ION CYCLOTRON RESONANCE SPECTROMETER P. N. T. VAN VELZEN, P. N. T. VAN VELZENSearch for more papers by this authorW. J. VAN DER HART, W. J. VAN DER HARTSearch for more papers by this authorJ. VAN DER GREEF, J. VAN DER GREEFSearch for more papers by this authorN. M. M. NIBBERING, N. M. M. NIBBERINGSearch for more papers by this authorM. L. GROSS, M. L. GROSSSearch for more papers by this author P. N. T. VAN VELZEN, P. N. T. VAN VELZENSearch for more papers by this authorW. J. VAN DER HART, W. J. VAN DER HARTSearch for more papers by this authorJ. VAN DER GREEF, J. VAN DER GREEFSearch for more papers by this authorN. M. M. NIBBERING, N. M. M. NIBBERINGSearch for more papers by this authorM. L. GROSS, M. L. GROSSSearch for more papers by this author First published: June 22, 1982 https://doi.org/10.1002/chin.198225098Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume13, Issue25June 22, 1982 RelatedInformation

A fourier transform ion cyclotron resonance study of the mechanism of formation of protonated dimethyl ether from methanol by use of naturally occurring 18O

AbstractIt is shown that ejection of mass selected ions of high abundance from the cell of a Fourier transform ion cyclotron resonance spectrometer permits the study of ion/molecule reactions of ions of very low abundance. Methanol is used as an illustration. Ejection of all ions with the exception of the 18O labelled protonated methanol molecules, present at natural abundance, shows that the protonated dimethyl ether molecules in this system are formed mainly by an SN2 displacement reaction.

Bimolecular production of proton bound dimers in the gas phase. A low pressure ion cyclotron resonance technique for examination of solvent exchange equilibria and determination of single molecule solvation energetics

A scheme is presented whereby sequences of fast bimolecular gas phase ion molecule reactions in mixtures containing (CHF2)2O may be used to generate proton bound dimer species at low pressures in an ion cyclotron resonance spectrometer. Using competitive solvent switching reactions it is demonstrated that solvent exchange equilibria may be readily established and from the thermochemical data derived from such equilibria accurate relative single molecule solvation energetics obtained.

An ion cyclotron resonance spectrometer as a gas chromatographic detector: Measurement of momentum transfer collision frequencies

The momentum transfer collision frequencies (ξ/ n) of 39K + with the three isomers of difluorobenzene are reported. The measurements have been done using ion cyclotron resonance techniques. Conventional linewidth measurements gave (ξ/ n) para = 1.71 ± 0.08 × 10 −9, (ξ/ n) meta = 2.18 ± 0.11 × 10 −9, and (ξ/ n) ortho = 2.79 ± 0.14 × 10 −9 cm 3 molecule −1 s −1. A method for measuring relative momentum transfer collision frequencies at resonance is described. The method involves coupling a gas chromatograph to the ion cyclotron resonance (ICR) spectrometer. Using this method it was found that (ξ/ n) ortho /(ξ/ n) para = 1.63±0.08, (ξ/ n) ortho /(ξ/ n) meta = 1.24±0.02, and (ξ/ n) meta /(ξ/ n) para = 1.32±0.07. The significance of the good agreement between the linewidth measurements and the measurements at resonance is discussed. The measurements are compared with those of Su and Bowers for the momentum transfer collision frequencies of 35Cl − with the difluorobenzene isomers. It is concluded that the momentum transfer rate constants are not affected significantly by a change in the sign of the ionic charge. The measurements are also compared with theory and found to agree with momentum transfer collision frequencies determined from a potential of the form Ar −8 - Br −6 - α e 2/2 r 4 + E ψ where the third term is the ion-induced dipole term and the fourth term is a statistically averaged ion-dipole term. The effect of ion/molecule reactions on the GC-ICR method and possible analytical applications of the method are discussed.

ChemInform Abstract: THRESHOLD RESONANCES IN THE ELECTRON PHOTODETACHMENT SPECTRUM OF ACETALDEHYDE ENOLATE ANION. EVIDENCE FOR A LOW‐LYING, DIPOLE‐SUPPORTED STATE

The electron photodetachment spectra for the enolate anions of acetaldehyde and acetaldehyde‐d3 have been measured using an ion cyclotron resonance spectrometer in conjunction with a tunable dye laser. Sharp resonances at threshold are observed for both anions, and are attributed to a low‐lying excited electronic state of the anion, which we relate to postulated ’’dipole‐supported’’ states of electron–polar molecule systems. The electron affinity of the neutral enolate radicals CH2CHO and CD2CDO are found to be 1.824±0.005 and 1.819±0.005 eV, respectively.

Dissociative excitation of gas-phase ions. A comparison of techniques utilizing ion cyclotron resonance spectroscopy and angle-resolved mass spectrometry

A comparison is made between electron-impact dissociation of ions in an ion cyclotron resonance (ICR) spectrometer and collision-induced dissociation performed in a mass spectrometer capable of selecting scattering-angles. These experiments both probe ion structure by monitoring unimolecular dissociation following excitation. The techniques have been applied to the molecular ions of trifluorotoluene, phenetole, aniline, n-propyl-benzene, and perfluoropropylene. Plots of relative fragment-ion abundance versus electron energy (in the range 2–9 eV) are compared to similar plots in which the abscissa is the scattering angle (known to be related in some systems to internal energy). The plots are found to be qualitatively similar for the two techniques for several of the molecular ions, but significantly different for two. For one of these, perfluoropropylene, a lack of dependence of fragment-ion abundance upon scattering angle was observed, implying that the ion internal energy does not vary with scattering angle. The differences between the electron- and particle-impact behavior may stem from the fact that fluorescence or rotational excitation are implicated. Although both methods suffer from some uncertainty in defining precisely the internal energy deposition they are simple to effect yet yield important fundamental information about ion dissociation chemistry.