Mass spectral metastable transitions determined by electric sector variation

Kiser, Robert W.; Sullivan, Richard E.; Lupin, M. S.

doi:10.1021/ac50159a029

Cited by 58 publications

(13 citation statements)

References 18 publications

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“…Although the signal does not fall to zero at the peak center, the steeply sloping side of the peak owing to the short slit heights used enables an adjacent broad peak to be resolved easily. This is illustrated in Figure 7 (a), which shows the corresponding peaks owing to the reactions C 6 H 5 D ++ -> C 5 H 3 + + CH 2 D + (6) and C 6 H 5 D ++ -*-C 5 H,D + + CH ;i + (7) in di-benzene. These peaks corre spond to approximately 10 ~5 of the total ion current, and this figure il lustrates the sensitivity of the spec trometer.…”

Section: Performance Of Instrumentmentioning

confidence: 94%

Design and Performance of a Mass-analyzed Ion Kinetic Energy (MIKE) Spectrometer

Beynon¹,

Cooks²,

Amy³

et al. 1973

Anal. Chem.

274

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Section: Performance Of Instrumentmentioning

confidence: 94%

Design and Performance of a Mass-analyzed Ion Kinetic Energy (MIKE) Spectrometer

Beynon¹,

Cooks²,

Amy³

et al. 1973

Anal. Chem.

274

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“…From (1) and (3) daughter ions from the fragmentation of metastable ions in the first field free region (f.f.r.l) will be transmitted by the electric sector if 4) and from (1) and (2) It may be seen from (4) and ( 5 ) that when the ion current is represented as a function of ln(Ip1) and In (Ipl), transitions of metastable ions in f.f.r.1 give rise to peaks centred over the point ( p = (m/z)J(~/z)~, p = ( m / z ) d ) and elongated in the p-direction because of kinetic energy release. Main beam ions undergo no change in kinetic energy in f.f.r.1, and give rise to peaks at ( p = 1, p = m/z), while metastable ion transitions in f.f.r.2 give rise to peaks centred on p = (m/z)d'/(m/z)p at p = 1 and broadened in the pdirection by kinetic energy release.…”

Section: Discussion and Resultsmentioning

confidence: 99%

A three‐dimensional representation of metastable peaks from double focusing mass spectrometers

Lacey

Macdonald

1977

Org. Mass Spectrom.

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The ion current transmitted by the collector slit of a double focusing maw spectrometer is considered as a function of two variables which independently reflect the effects of the instrument's electric and magnetic sectors. The ionic products of reactions occurring in the source and in various regions of the llight tube give rise to peaks or ridges with distinctive shapes and positions in the surface so derived. Volumes under peaks are proportional to abundances of ions. The surface provides a unified view of the alternative methods of scanning and Eaditates understanding of the contrasting perspectives of metastable peaks which they reveal. The method, which may be applied with instruments of either conventional or reversed geometry, is illustrated for the former by reference to that part of the surface for toluene which relates to the loss of H from the molecular ion.Spontaneous and collision induced ion transitions in the flight tube of a mass spectrometer provide valuable information for establishing fragmentation sequences, ionic structures and molecular homogeneity. Further, the spontaneous reactions are representative of ion energies close to the reaction thresholds and can be more sensitive to molecular peculiarities than the faster processes occurring in the ion source at 70eV. Assessments of spontaneous and collision induced ion transitions are therefore of increasing importance in mass ~pectrornetry.'-~ In studies of the reactions of metastable ions in a double focusing mass spectrometer the ion current transmitted by the collector slit may be recorded as a function of a number of independently varied instrumental parameters, of which the accelerating voltage V, the electric sector voltage E, and the magnetic field B are usually the most important. Interpretation of data obtained in this way may be facilitated by constructing from them a three-dimensional surface in which the ion current: is considered as a function of two variables, each of which is derived from V, E and B. For example, data relating to reactions of metastable ions have been displayed by means of projections of three-dimensional plots of ion current against m* and P,"-~ and schematic contour maps of ion current against M, and mJy.8 Computer techniques for assisting the visualization of three-dimensional surfaces are well established and may be implemented readily on many general purpose computer installations with facilities for graphical output. METHODWe define symbols p and p such that p = ( Vo/V)(E/Eo) and p = (Eo/E)mB where Vo and Eo are t Author to whom correspondence should be addressed. @ Heyden 8 Son Ltd, 1977 reference values of V and E at which the main ion beam is transmitted by the electric sector, and mB, a convenient measure of B, is the mass of singly charged main beam ions transmitted by the magnetic sector when V = Vo and E = Eo. The definition of p is an extension of one used p r e v i~u s l y .~~We shall represent the ion current transmitted by the instrument's collector slit as a function of In (IpI) and In ([pi). ...

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“…A given ratio V,/V, = m21m1 measured from the IKE spectrum combined with the m* value recorded on the magnetic scan of the spectrum provides the needed variables to compute the metastable transitions unambiguously. 8 In this study, IKE spectra were recorded for various compounds to determine their value in providing useful information on molecular structure. The measured electrostatic sector voltage is shown over each IKE peak in the spectra reported.…”

Section: R E S U L T S a N D Discussionmentioning

confidence: 99%

Ion kinetic energy spectroscopy

Chait

Askew

1971

Org. Mass Spectrom.

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Abstract-Preliminary results indicate the value of ion kinetic energy (IKE) spectra in adding a new dimension to structural information obtained by mass spectrometry. These spectra are especially useful in the distinction of some isomer pairs. Energy spectra provide a summary of gaseous ion chemistry occurring as metastable transitions in the first-field free-drift region of the double-focusing (Mattauch-Herzog geometry) mass spectrometer and are produced by scanning the electrostatic sector voltage while recording the ion? transmitted by the sector with the beam monitor electrometer. I N T R O D U C T I O NTHE TECHNiQuE of defocusing the double-focusing mass spectrometer for the sensitive observation of metastable ions and assignment of metastable transitions is well established1,2 and has been discussed specifically for mass spectrometers of the Mattauch-Herzog A variation of this technique produces a unique spectrum for the metastable transitions observed for a particular compound. Production of these ion kinetic energy (IKE) spectra was first demonstrated by Beynon5s7 using double-focusing instruments of the Nier-Johnson geometry. In this report, results obtained using an instrument of the Mattauch-Herzog geometry are sunimarized.In defocused metastable experiments described previously, the daughter ions from the precursor decompositions are observed by variation of the magnetic field to focus the mass in2 or m t as allowed by the appropriate accelerating or electrostatic sector voltage. If, however, only kinetic energy of the daughter ions is considered, a spectrum of the metastable transitions of a particular sample may be recorded without consideration of the mass. R E S U L T S A N D DISCUSSIONIf the electrostatic sector of the mass spectrometer is scanned, the individual ion beams of varying kinetic energy resulting from the daughter ions of metastable decompositions may be scanned across the electrodes of the beam monitor. The resultant IKE spectrum plots the kinetic energy 1's. abundance of daughter ions allowing a summary of all metastable transitions in a single experiment. A typical IKE spectrum for decane is shown in Fig. I .The main or normally focused beam of the mass Spectrometer with an ion accelerating voltage (kinetic energy) of 8 kV is observed at an electrostatic sector voltage of 400 Vr producing an intense ion signal at the left hand side of the spectrum.

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Mass spectral metastable transitions determined by electric sector variation

Cited by 58 publications

References 18 publications

Design and Performance of a Mass-analyzed Ion Kinetic Energy (MIKE) Spectrometer

Design and Performance of a Mass-analyzed Ion Kinetic Energy (MIKE) Spectrometer

A three‐dimensional representation of metastable peaks from double focusing mass spectrometers

Ion kinetic energy spectroscopy

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