Series Of Cluster Ions Research Articles

Mass distribution of sulfide cluster ions, X nS m± (XC, Si, Ge)

A series of binary cluster ions composed of sulfur and group IVA elements, X n S m ± (XC, Si, Ge), were generated by direct laser vaporization. Their mass distribution was recorded by a time-of-flight mass spectrometer. The relative abundance of most carbon-sulfur and silicon-sulfur cluster ions can be described by the statistical distribution rule. The carbon-sulfur cluster ions containing a single sulfur atom have a strong affinity for trapping an extra hydrogen atom and their signal intensity exhibits a dramatic even/odd alternation. Parity of the alternation effect depends on the positive or negative charge carried by the cluster ions. The cluster ions containing two sulfur atoms show higher signal intensity and their alternation effect is not affected by the polarity. Most silicon-sulfur cluster anions can be described by two log-normal curves. One series of cluster ions can be represented as (Si 2S 8)(SiS 2) n −, and the other as (Si 2S 7)(SiS 2) −. Both series of cluster ions take SiS 2 as the growing unit. Analysis of the mass distribution suggests that both carbon-sulfur and silicon-sulfur cluster ions adopt a low-dimensional geometry. However, for the former, sulfur atoms are located at the end of the C-C chain; for the latter, sulfur atoms bridge the clustering silicon atoms. Germanium and sulfur can only form small cluster anions. The signal intensity of germanium-sulfur cluster anions, Ge n S m −, drops rapidly with the increase in n. Generally, the bonding nature of the cluster ions X n S m ± changes from covalent to ionic as X changes from carbon to germanium.

Formation of Sodium Cluster Ions in Electrospray Mass Spectrometry

A series of sodium cluster ions, such as Na+(NaCl)n, Na+(HCOONa)n and Na+(HCOONa)n1(CH3COONa)n2, were observed in electrospray mass spectrometry. These results support the electrophoretic separation mechanism for excess ions at droplet surface, and the charged residue model for gas phase ion formation from highly-charged droplets.

MeV atomic ion sputtering of fullerenes: a radial velocity distribution study

We report swift heavy-ion-induced sputtering of carbon cluster ions from fullerene-containing and polymer thin films (pure C 60, fluorinated C 60(C 60F m , 24 < m < 48), blends of pure C 60 with polystyrene (PS/C 60), and poly(vinylidene fluoride) (PVDF)). Intact C 60 molecular ions and their fragments (C 60-2 n , 1 < n < 5), together with a series of higher mass carbon cluster ions (C 60+2 n , n from 1 to at least 100) are ejected as a result of the interaction of an individual MeV ion with the various targets. The intensity patterns of the higher mass carbon cluster ion series depend on the type of bombarded target. For pure C 60 targets the high mass clusters have higher yields around multiples of 60 (C 120 and C 180). In the case of PS/C 60, C 60F m and PVDF targets, the cluster intensity decreases continuously with increasing cluster size. Measurements of the initial radial velocity distributions of such cluster ions have been performed in a reflectron time-of-flight mass spectrometer, using 72.3 MeV 127I 13+ as primary ions. The radial velocity distributions of the sputtered ions are indicative of the processes of their formation: condensation of hot carbon atom “gas” in the core of the ion tracks versus coalescence of C 60 molecules, most probably in the gas phase.

Ammonium Nitrate Cluster Ions

Sputtering of condensed-phase ammonium nitrate yields many positive and negative cluster ion series derived from different ionic cores. The cluster cores are surrounded by varying numbers of ammoni...

Mass distribution of cluster ions produced from laser ablation of metal-composite-oxides Y-M-Cu-O (M=Ba, Sr, Ca, Mg)

Laser ablation of YMCuO metal-composite-oxides (M=Ba, Sr, Ca, Mg) in high vacuum produced cluster ions with various sizes and compositions. Mass spectra of the cluster ions were recorded by a home-built time-of-flight (TOF) mass spectrometer and the mass distributions were analyzed by a statistical model. For YBa2Cu3O7−x (YBCO) high-Tc superconducting samples, six series of cluster ions were observed. Replacement of barium in the metal-composite-oxide sample with other alkaline earth metal, such as strontium, calcium, or magnesium, not only removed the superconductivity, but also changed the compositions and distributions of the laser generated cluster ions. For instance, copper was only found in the compositions of cluster ions generated from YBCO sample. From comparison of the experimental results, interactions among components of the metal-composite-oxides and the function of alkaline earth metal in superconducting material were discussed.

Formation and coalescence of fullerene ions from direct laser vaporization

A series of carbon cluster ions have been created by direct laser vaporization of elementary carbons and organic compounds with different structures and compositions. The mass spectra of the carbon cluster ions were recorded in situ by a time-of-flight mass spectrometer and the experimental results showed that the formation of fullerenes and their relative abundances are closely related to the surface structure of the sample. Under direct laser vaporization, the products from a perfect (0001) surface of graphite were mainly C60 and C70. The surface perpendicular to the (0001) plane of graphite could not produce C60, other fullerene ions or compounds containing six-membered aromatic carbon rings. The products of amorphous carbon and aromatic compounds included C60 and other fullerenes, among which those with a mass twice that of C60 were most abundant. Furthermore, C60 and C70 could also be aggregated from direct laser vaporization. Based on these experimental results, mechanism for formation of C60 and other fullerenes is suggested.

Pulsed laser deposition of carbon films: Dependence of film properties on laser wavelength

We have grown thin carbon films by pulsed laser deposition and have investigated the extent to which the properties of such films, as well as the processes responsible for these properties, are laser wavelength dependent. Films were grown by ablating material from a graphite target onto room temperature Si(100) substrates with 1064 and 248 nm laser radiation. The films were analyzed by in situ electron energy loss spectroscopy and by ex situ Raman spectroscopy. The results indicated that films grown with 1064 nm ablation were graphitic, while those grown with 248 nm radiation were diamond-like. We have also examined the mass and kinetic energy distributions of the particles ejected from graphite by the two laser wavelengths. The results indicated that irradiation of graphite with 1064 nm laser radiation results in the ejection of a series of carbon cluster ions C{sub n}{sup +}(1=30) with mean kinetic energies less than 5 eV. Ablation of graphite with 248 nm radiation results in the ejection of primarily C{sub 2}{sup +} and C{sub 3}{sup +} with mean kinetic energies of 60 and 18 eV, respectively. These results suggest that large, low energy clusters produce graphite films, while small, high energy clusters produce films of diamond-likemore » carbon. 17 refs., 5 figs., 1 tab.« less

Mass Spectrometric Investigation of Dimethoxyethane Clusters: Complete Solvation of a Protonated Cation

We present mass spectrometric results for van der Waals clusters composed of dimethoxyethane molecules (CH 3 OCH 2 CH 2 OCH 3 ≡DMEt). The protonated dimethoxyethane cluster ions (DMEt) n H + were observed to form the most intense cluster ion series. A number of other cluster ion sequences including (DMEt) n (CH 3 -OH)H + and (DMEt) n (H 2 O)H + were also observed. In a separate tandem mass spectrometric study, we observe that the collision-induced dissociation spectra of (DMEt) n H + (n=1, 2) yield CH 3 OH 2 + and H 3 O + cations

Mass Analysis of Silver-Carbon Mixed Cluster Ions Produced by Fast Atom Bombardment

A regular series of silver-carbon mixed cluster ions: AgmC2n(m=3, 5, 7, 9; n=1, 2, 3) has been found by mass spectrometry. This regularity is not destroyed by the energetic collisions of the cluster ions with argon atoms. Remarkable differences are observed in the chemical species produced between the cluster ions containing odd numbers of silver atoms and those containing even numbers of silver atoms. Size-selected reactions of the cluster ions with argon clearly show the magic numbers effect, in addition to the even-odd difference. The mechanism of formation of silver-carbon mixed cluster ions is studied. The authors propose that the mixed cluster ions are produced on a silver surface through decomposition and dehydrogenation of hydrocarbon molecules contained in the background gas of the ionization chamber. This picture is consistent with observations from scanning tunneling microscopy.

The Formation and Photodissociation of Copper-Sulfur Cluster Ions

Copper suffer cluster ions were produced by laser ablation on solid samples: (1) a mixture of copper and sulfur powder, (2) cuprous sulfide compound, (3) cupric sulfide compound, respectively. Two main series of cluster ions were found: (a) [Cu(Cu2S)(n)](+) (n = 0 - 22), (b) [(Cu2S)(n)](+) (n = 1 - 18). The main photodissociation channels of the cluster ions were neutral losses of Cu2S, Cu or CuS. It is obvious that the Cu2S unit plays an important role in the formation and structure of the Cu/S cluster ions, and furthermore, the filled d(10) shell eletronic configuration of copper element might be critical to the characteristic of the cluster ions.

Application of 252Cf plasma desorption mass spectrometry in dental research

Topically applied fluorides introduced in dental hygiene products elevate the concentration levels of fluoride in oral fluids and thus also affect chemical reactions of enamel de- and remineralisation. The chemical reactions on the surface of tooth enamel still are a subject of controversy. Here 252Cf-plasma desorption mass spectrometry and argon ion etching are used to analyse the molecular structure of the upper layes of enamel. The mass spectrum of untreated enamel is characterised by a series of cluster ions containing phosphate. It is evident that under certain conditions the molecular structure of the surface enamel is completely transformed by treatment with fluorides. The result of the degradation and precipitation processes is reflected by a total replacement of the phosphate by fluoride in the measured cluster ion distribution. Stepwise etching of the upper layers by Ar + ions reveals the transition from a nearly pure CaF 2 structure to the unchanged composition of the enamel mineral.

Mass spectrometric investigation of 2-methoxyethanol and 2-ethoxyethanol clusters: magic numbers and structural implications

Abstract : In this paper we present the results of our mass spectrometric investigations for van der Waals clusters of 2-methoxyethanol and 2- ethoxyethanol. The cluster mass spectra were acquired for a variety of expansion conditions and electron energies. The protonated alkoxyethanol cluster ions (AE)nH(+) form the dominant cluster ion series. A number of fragment ions, that may arise from an unprotonated and/or a protonated alkoxyethanol molecular ion, were solvated by additional alkoxyethanol molecules. The (AE)n(H20)mH(+) ions were observed with significant intensities only for n >/= 5 in neat as well as mixed alkoxyethanol/water expansions. It was also found that (AE) n (H20)m H(+) cluster ions which satisfy the condition n = 2 (m + 2), for m = 1 and 2, have enhanced ion intensities. The various models that may explain the behavior of (AE)n(H20)mH(+) are discussed.

Substitution reactions in the secondary ion mass spectrometry of N‐methylpyridinium halides

AbstractSecondary ion mass spectra of N‐methylpyridinium halides (C+X−, where C+ is a pyridinium cation and X− is a halogen anion) exhibit the C+ ions, a series of cluster ions ((C+)n(X−)n–1) and, furthermore, remarkable [CX – R]+ ions (R = H or Me). The mechanism of the formation of [CX – R]+ ions was investigated by the use of deuterated compounds and B/E and B2/E constant linked‐scan measurements. A possible explanation is proposed in which the ions are produced through substitution reactions between species constituting the C2X+ cluster ions in the gas phase.

The decay dynamics of photoexcited argon cluster ions

Following the photoexcitation of argon cluster ions, Ar+n for n in the range 4–25, kinetic energy release measurements have been undertaken on the fragments using two quite separate techniques. For Ar+4–Ar+6, fragment ion kinetic energy spectra were recorded at 532 nm in a crossed beam apparatus as a function of the angle of polarization of the laser radiation with respect to the incident ion beam. Only Ar+ from Ar+4 was observed to exhibit a polarization dependence together with a comparatively high kinetic energy release. The principal fragment ion Ar+2 was found both to emerge with a low kinetic energy release and to display no dependence on the angle of polarization of the radiation. In a second series of experiments, mass and kinetic energy resolved cluster ions were photodissociated in the entrance to a time-of-flight (TOF) device of variable length. The subsequent deflection of all ions allowed for time resolved measurements to be undertaken on the neutral photofragments. Following the absorption of a photon, all cluster ions up to Ar+25 were found to eject one/two neutral atoms with comparatively high kinetic energies. Any remaining internal energy appears to be dissipated through the loss of further neutral atoms with low kinetic energies. An analysis of the laser polarization dependence of these events, shows that those atoms identified as having high kinetic energies are ejected on a time scale which is short compared with the rotation period of a cluster (≂10 ps). These experimental observations are consistent with the results of recent molecular dynamics simulations of excited states in rare gas clusters by Landman, Jortner, and co-workers [J. Phys. Chem. 91, 4890 (1987); J. Chem. Phys. 88, 4273 (1988)]. Kinetic energy releases calculated from the TOF spectra exhibit marked fluctuations as a function of cluster size, with Ar+15 showing a minimum and Ar+19 a maximum. It is suggested that such behavior is part of a dynamic response to changes in structure as the cluster ions increase in size. A qualitative explanation is provided through the assumption that the cluster ions take the form of solvated Ar+2 structures. Considerations of the energy available from the photon and the relative contribution each TOF feature makes to the total signal, places an upper limit of two as the number of high kinetic energy atoms ejected by the larger cluster ions.

Metastable transitions and isotope distribution identification program for use in mass spectrometry involving spectra with multiple coincidences

We have developed a user program—written in JPI Top Speed Modula2 for IBM-AT compatible computers—which allows one to predict and identify, for a given cluster ion series, possible coincidences in (i) the ordinary mass spectrum and (ii) for metastable and collision-induced decay reactions in the first and second field-free regions of a double focussing sector field instrument. The capability of this program will be demonstrated by discussing several selected examples. The program may be obtained free of charge from the authors.

Morphology and reactivity of ions and cluster ions produced by the laser ablation of yttrium barium copper oxide (YBa2Cu3O7-.delta.) superconductor

Laser ablation of YBa 2 Cu 3 O 7-δ (YBCO) superconducfor samples was investigated in a Fourier transform ion cyclotron resonance mass spectrometer (FTICR-MS) to determine the morphology of the cluster ions produced. Cluster ion series increase exclusively by addition of BaO and Y 2 O 3 neutral species. Collisionally induced dissociation (CID) of the clusters indicated that BaO was coordinated to the yttrium atoms, leading to preferential loss of BaO, but was coordinated to other BaO units in copper clusters, where Cu loss was observed

Study of protonated methanol cluster ions under thermal conditions

Size-dependent intracluster reactions within the methanol cluster system are studied using a fast flow reactor operated under thermal conditions. At low temperature, large protonated methanol cluster ions (CH 3OH) n H + ( n up to 24) are produced for the first time under thermal conditions. Two mixed cluster ion series of (CH 3OH)) n (CH 3OCH 3)H + and (CH 3OH) n (H 2O)H + are also observed. Interestingly, the cluster ion patterns are found to be greatly influenced by the degree of solvation, due to several size specific intracluster ion—molecule reactions. The mixed cluster ions (CH 3OH) n (CH 3OCH 3)H + are observed only for the small clusters ( n⩽5) while the mixed cluster ions (CH 3OH) n (H 2O)H + are seen only for the large ones ( n⩾7). The work reported herein is particularly significant in that it demonstrates under thermal conditions, the influence of the degree of solvation on the course of intracluster ion—molecule reactions. Moreover, these new findings further support what is becoming a general observation concerning the role of the number of bonding sites in affecting the chemical nature of the ion core in mixed clusters.

Cluster ions in the secondary ion mass spectrometry of choline and acetylcholine halides

AbstractLiquid secondary ion mass spectra of choline and acetylcholine halides exhibit several series of cluster ions whose origins were investigated using B/E and B2/E linked‐scan techniques. In the case of choline halides three series of cluster ions were identified as (Me3\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ + $\end{document}CH2CH2OH + nM), (Me3\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ + $\end{document}CH2CH2OMe + nM) and (Me3N\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ + $\end{document}CH2CH2OH · Me3\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ + $\end{document}CH2CH2O− + nM), while (CH3COOCH2CH2\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ + $\end{document}Me3 + nM), (Me3\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ + $\end{document}CH2CH2OH + nM) and (CH2 = CH\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ + $\end{document}Me3 + nM) were observed in the spectra of acetylcholine halides. For these cluster ions, bimolecular reactions induced on ion bombardment under secondary ion mass spectrometric conditions are discussed.

Transfer of vibrational energy in nitrogen clusters doped with O 2: New evidence for the origin of quantum effects in the metastable decay series of (N 2) n+*

The decomposition of metastable (N 2) n +*, ((N 2) nO 2) +* and (0 2) n +* ions ( n up to 10) has been studied quantit a double-focusing sector field mass spectrometer as a function of cluster size n, and the number of evaporated neutral monomers p (with p up to n-1 for each cluster ion series). Whereas (N 2) n +* cluster ions show the known oscillatory pattern in the evapor probability versus the number of evaporated monomers (attributed to radiationless relaxation of vibrationally excited N 2 molecules in clusters), nitrogen cluster ions doped with one O 2 molecule do not show this behavior. In accordance with observations in liquids, this finding is interpreted as being due to an increased relaxation rate in the presence of the O 2 dopant.

ChemInform Abstract: Ion‐Molecule Reactions Within Methane Clusters Initiated by Photoionization

ChemInformVolume 18, Issue 37 Physical Organic Chemistry ChemInform Abstract: Ion-Molecule Reactions Within Methane Clusters Initiated by Photoionization A. DING, A. DING Bereich Strahlenchem., Hahn-Meitner-Inst., D-1000 BerlinSearch for more papers by this authorR. A. CASSIDY, R. A. CASSIDY Bereich Strahlenchem., Hahn-Meitner-Inst., D-1000 BerlinSearch for more papers by this authorJ. H. FUTRELL, J. H. FUTRELL Bereich Strahlenchem., Hahn-Meitner-Inst., D-1000 BerlinSearch for more papers by this authorL. CORDIS, L. CORDIS Bereich Strahlenchem., Hahn-Meitner-Inst., D-1000 BerlinSearch for more papers by this author A. DING, A. DING Bereich Strahlenchem., Hahn-Meitner-Inst., D-1000 BerlinSearch for more papers by this authorR. A. CASSIDY, R. A. CASSIDY Bereich Strahlenchem., Hahn-Meitner-Inst., D-1000 BerlinSearch for more papers by this authorJ. H. FUTRELL, J. H. FUTRELL Bereich Strahlenchem., Hahn-Meitner-Inst., D-1000 BerlinSearch for more papers by this authorL. CORDIS, L. CORDIS Bereich Strahlenchem., Hahn-Meitner-Inst., D-1000 BerlinSearch for more papers by this author First published: September 15, 1987 https://doi.org/10.1002/chin.198737041Read 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 onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume18, Issue37September 15, 1987 RelatedInformation