Ion Source Of Mass Spectrometer Research Articles

Ion source of quadrupole type mass spectrometer for isotope measurement of UF6.

Ion source of quadrupole type mass spectrometer for isotope measurement of UF6.

Isotope ratios in photosynthetic oxygen

Axenic suspensions of the fresh water green alga Ankistrodesmus braunii were illuminated under aerobic conditions. The released gas mixture was introduced into the ion source of an isotope mass spectrometer, which recorded the 18 O 16 O ratio. The 18O content of the photosynthetic oxygen (≈0.199%) exceeded that of the cell water (≈0.197%) significantly.

Fast radical reactions in a mass spectrometer ion source: radical addition to 7,7,8,8-tetracyanoquinodimethane

Fast radical reactions in a mass spectrometer ion source: radical addition to 7,7,8,8-tetracyanoquinodimethane

Calibration of mass spectrometers for van der Waals dimers

A stream tube from a small supersonic free jet in vacuo is passed successively through the ion source of a quadrupole mass spectrometer and into an enclosed ionization gauge which indicates total mass flux. By simultaneous measurements of dimer and monomer ion currents as well as total mass flux we are able to arrive at absolute values of the relative concentration of neutral monomer and dimer in the free jet. Results obtained with argon, carbon dioxide, and oxygen indicate substantial fragmentation of dimers in the ion source. Consequently, populations of neutral dimers in supersonic free jets of the kind widely used as beam sources may be much larger than previous studies have indicated.

Chemical ionization mass spectrometry as a tool for the elimination of surface related phenomena in the spectra of unstable compounds

The occurrence of surface related reactions in mass spectrometer ion sources has long been recognized. The products of gas--surface reactions, involving surface ionization on the filament and pyrolysis on hot surfaces, often contribute minor peaks to electron impact (EI) mass spectra, and complications can be severe in the analysis of reactive or thermally unstable compounds. The resulting mass spectra may lead to an assumption of the presence of impurities not actually in the sample, or even cause errors in the identification of unknown compounds and mixtures. The purpose of this correspondence is to present an example of such surface related phenomena and to point out how these problems may be avoided utilizing chemical ionization (CI) mass spectrometry. The compound used to illustrate this problem is the brominated derivative of polymeric, sulfur nitride, (SN)/sub x/. (SN)/sub x/ has been previously found to produce a noncyclic (SN)/sub 4/ species upon sublimation. The brominated derivative, of empirical formula SNBr/sub 0/./sub 4/, was expected to yield (SN)/sub 4/ plus an unknown brominated species upon sublimation; hence, identification of the bromine containing species was of particular interest. Results show that argon (in the absence of a large water impurity) offers a distinct advantage for themore » analysis of mixtures over more commonly used methane, isobutane, and ammonia as a CI reagent. The latter involve relatively low energy proton transfer processes; hence, molecular species such as Br/sub 2/ and S/sub 8/ are not ionized by isobutane and NH/sub 3/ CI. Charge transfer from argon ions (Ar/sup +/ and Ar/sub 2//sup +/ are the major reagent ions in this work) is a much higher energy process and is capable of ionizing most molecules. (JRD)« less

Molecular velocity distribution effects in kinetic studies by time-resolved mass spectrometry

Mathematical models were developed to describe the sampling of a rapidly reacting gas by time-resolved mass spectrometry. The flow of reaction mixture from a sampling orifice in the reactor wall to the mass spectrometer ion source was treated by application of the Boltzmann equation. The calculations demonstrate that for sufficiently rapid reactions the molecular velocity distribution of the detected species causes a distribution of arrival times at the ion source which complicates the kinetic analysis. The time-dependent signal is composed of two parts; one due to the rate of chemical reaction and the other due to the ion source arrival time distribution. Calculations done on the basis of both first and second order kinetics indicate the upper limit to the reaction rate which can be measured without causing substantial errors in rate constant determinations when conventional types of concentration time plots are used. These limits hold for effusive flow through the orifice, and at least to a first approximation also hold for convective and transition flow.

Cleaning of mass spectrometer ion sources by electropolishing

Cleaning of mass spectrometer ion sources by electropolishing

Polymerization of lactams—XVI: Cyclic oligomers in copolymers of 6-caprolactam with 8-octanelactam and their determination by mass spectroscopy

The methanolic extract of a copolymer of 6-caprolactam with 8-octanelactam was analyzed; cyclic oligomers were identified by mass spectroscopy. The cyclic homodimers and codimer were separated by thin-layer chromatography. The quantitative analysis of methanolic extract involved direct evaporation into the ion source of mass spectrometer.

Studies of reactions of importance in the stratosphere. I. Reaction of nitric oxide with ozone

The rate constant for the reaction NO+O3→NO2+O2 has been measured by the fast flow method over the temperature range 203–361 K. Loss of ozone in a large excess of nitric oxide was detected by molecular beam sampling into the electron impact ion source of a quadrupole mass spectrometer. The resulting Arrhenius expression is k=2.34±0.23×10−12 exp(−1450±50/T) cm3 molecule−1 s−1 which predicts k298=1.80×10−14 cm3 molecule−1 s in excellent agreement with previous determinations. Our results suggest a slight curvature in the Arrhenius plot, the activation energy increasing with increasing temperature.

Display device for ion beam profile

A display device for ion beam profiles which permits the study of mass spectrometer ion source performance is presented. In this device the ion beam from the source is deflected by two pairs of plate electrodes, and a small portion of the beam’s cross section is directed through a 50-μm aperture. Thus, the sampling spot of the beam’s cross section is scanned as in a TV. The analog signal of the detected ion current is fed into an equistrength signal generator and converted into pulses, which are used to modify the brightness of a CRT. At the same time, the flying spot on the CRT is synchronized with the ion beam scanning. Thus, the intensity distribution of the beam’s cross section is displayed as equistrength lines on the CRT.

Atomic oxygen-metal surface studies as applied to mass spectrometer measurements of upper planetary atmospheres

The problem of atomic oxygen loss in mass spectrometer ion sources can be reduced to an understanding of the possible surface interactions between oxygen atoms and the metal surface of the ion source. Results are presented for an experimental study in which an atomic oxygen beam apparatus and a mass spectrometer were used to measure the oxygen atom reflection, recombination, general surface reaction, and occlusion probabilities on six different engineering surfaces as a function of atomic oxygen exposure. The materials studied are gold, Nichrome V, aluminum, titanium, silver, and platinum. The variation in measured reflection probability seems to occur with metals that form oxides, Nichrome V being stable in terms of reflection stability. Recombination is observed an all surfaces except aluminum and platinum. Variation in the complete set of measurements in a single experiment is the result of varying surface conditions.

ChemInform Abstract: STABILITY AND STRUCTURE OF H3CO(+) FORMED FROM COH(+) + H2 AT LOW TEMPERATURE

Chemischer InformationsdienstVolume 6, Issue 44 Physical Organic Chemistry ChemInform Abstract: STABILITY AND STRUCTURE OF H3CO(+) FORMED FROM COH(+) + H2 AT LOW TEMPERATURE KENZO HIRAOKA, KENZO HIRAOKASearch for more papers by this authorPAUL KEBARLE, PAUL KEBARLESearch for more papers by this author KENZO HIRAOKA, KENZO HIRAOKASearch for more papers by this authorPAUL KEBARLE, PAUL KEBARLESearch for more papers by this author First published: November 4, 1975 https://doi.org/10.1002/chin.197544060AboutPDF 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. Volume6, Issue44November 4, 1975 RelatedInformation

THE PHOTOLYSIS OF VINYL IODIDE AND THE MASS SPECTRUM OF VINYL RADICAL

Abstract The photolysis of vinyl iodide has been studied using UV light beam of high intensity and a collision-free photochemical reactor incorporated in the ion-source of mass spectrometer. The primary process C2H3I + hν → C2H3 + I was found predominant and the process C2H3I + hν → C2H2 + HI minor, and the mass spectrum of vinyl radical was obtained.

Stability and structure of H3CO+ formed from COH++H2 at low temperature

The gas phase equilibrium (1) HCO++H2 = H3CO+ was studied in the temperature range −100 to −165 °C with a pulsed electron beam high pressure ion source mass spectrometer. Van’t Hoff plots of K1 led to ΔH °1 = −3.9 kcal/mole and ΔS °1 = −20.5 e.u. (stand. state 1 atm). This ΔH1 and standard thermochemical data lead to ΔHf(H3CO+) = 196.8 kcal/mole. Thus the H3CO+ formed by (1) is not protonated formaldehyde H2COH+ whose ΔHf = 169.8 kcal/mole. The reactivity of H3CO+ observed in ion molecule reactions and the theoretically predicted charge distribution in HCO+ suggest that the structure of H3CO+ is an HCO+ in which the partially positive hydrogen forms a weak three center bond with an H2. This bond is similar to, but weaker than the bond occurring between H3+ and H2 in the H5+ molecule.

Temperature dependence of bimolecular ion molecule reactions. The reaction C2H5++CH4 = C3H7++H2

The reaction C2H5++CH4 = C3H7++H2 [Reaction (1)] was observed in pure methane in a pulsed electron beam high pressure ion source mass spectrometer. The rate constants k1 determined in the temperature range 250–650 °K were found to increase with temperature. An Arrhenius plot of k1 gave a straight line which yields 6×10−13 cm3 molecule−1⋅sec−1 for the preexponential factor and 2.5 kcal/mole for the activation energy E1. At temperatures below 250 °K, Reaction (1) was gradually replaced by (8): C2H5++2CH4 = C3H9++CH4. It is concluded that both (1) and (8) proceed by the excited intermediate (C3H9+) * which may back react to C2H5++CH4, decompose to C3H7++H2, or be stabilized to C3H9+. The positive temperature dependence of (1) arises from an internal energy barrier B between the three center bonded structures: x x x x The lowest energy structure IV is formed by the addition of C2H5+ to CH4. The H2 elimination from C3H9+ must proceed via structure III. The barrier B = ΔH8+Ea(1) = 6.6+2.5 kcal/mole is larger than the barrier A for back dissociation of C3H9+ to C2H5++CH4, where A = ΔH8 = 6.6 kcal/mole. Thus at low temperature back dissociation predominates, while at higher temperatures H2 elimination becomes competitive.

A new field ion emitter for field ion sources of quadrupole mass spectrometers

When compared with the wire emitters usually employed, a fivefold increase in sensitivity of the quadrupole mass spectrometer for the field ionization of gases is obtained.

Presence of the methylester of 5-carboxymethyl uridine in the wobble position of the anticodon of tRNA ArgIII from brewer's yeast

The methylester of 5-carboxymethyluridine (mcm5U), its degradation product 5-carboxymethyluridine (cm5U) and the corresponding nucleotide (cm5Up) were isolated from brewer's yeast tRNAIII Arg or from the dodecanucleotide containing the anticodon. Their chromatographic and electrophoretic properties and their UV absorbing spectra were identical to that of the corresponding synthetic compounds. The gas chromatographic behavior and the mass spectrum of mcm5U obtained from tRNAIII Arg and of a synthetic sample were also identical ; the rare occurence of a thermal reciprocal bimolecular methyl-hydrogen transfer in the mass spectrometer ion source was observed. A mild alkaline treatment of tRNAIII Arg leads to the saponification of mcm5U into cm5U (within the tRNA), which can be again esterified in the presence of a yeast homogenate and (methyl-14C) S adenosylmethionine. The radioactivity was found in the mcm5U located in the wobble position of the anticodon of tRNAIII Arg. The presence of this odd nucleotide in that position could possibly restrict the codon-anticodon interaction of tRNAIII Arg.

Isotopic Analysis of Molybdenum by Surface Ionization Mass Spectrometry and a Carbonization Technique

A technique to increase and stabilize the ion production of molybdenum and some other elements has been developed in their isotopic analysis by single-filament surface ionization mass spectrometry. A mixture of the element (5-100μg, dilute sulfuric acid solution)and five to ten as much glycerol(5v/v% aqueous solution purified by ion exchange)was mounted on a ribbon filament and was charred in air to slightly wet tar, and then heated in the mass spectrometer ion source under a vacuum of-5×10-7 Torr to appropriate temperatures by slowly increasing the filament current. As the filament material, rhenium ribbon was suitable for Mo and Hf, and tantalum ribbon for Cr samples. The sample coated in the form of oxo-compounds was reduced possibly through intermediate or direct carbonization during mass spectrometry and the sample pretreatment outside or inside the instrument was shortened. Stable ion currents of 10-13; to 10-11 A for Mo+, Hf+, and Cr+ ions were obtained and found to be usable in routine isotopic analysis.

Primary and chain carrier ions participating in the gas phase polymerization of ethylene oxide

The positive ion reactions leading to the initial steps in the polymerization of ethylene oxide have been investigated in the β ion source of a high pressure mass spectrometer. Primary and chain carrier ions up to C8H15O+4 have been identified in the spectra of the pure monomer. In mixtures of NH3 and C2H4O, polymeric ions C8H21O+4 have been detected. The observed proton transfer reactions between H+3, H3O+, CH+5, C2H+5 and C2H4O confirm that C2H5O+ is the initiator of the main polymerization chain.

Positive ion reactions of methyl chloride in the gas phase

The positive ion reactions of methyl chloride in the gas mixtures CH 3ClH 2 and CH 3ClN 2 have been examined in a high pressure ion-source mass spectrometer at pressures from 0.1 to 2 torr and at temperatures between 165 and 360 K. The formation of the CH 2Cl +(CH 3Cl) n, CH 3ClH +(CH 3Cl) n and [H 3CClCH 3] + (CH 3Cl) n clusters have been observed, and the solvation enthalpies for these clusters were derived from the appropriate van't Hoff plots. The calculations of potential energy of the [H 3CClCH 3] + ion and the charge distribution in the [H 3CClCH 3] +(CH 3Cl) 2 species are reported.