0000000000075720
AUTHOR
A. J. Bell
Fragmentations and reactions of protonated O,O-dimethyl ethylphosphonate and some isotopomers produced by electrospray ionisation in an ion trap mass spectrometer
Abstract The fragmentation behaviour of protonated O , O -dimethyl ethylphosphonate and its isotopomers deuterated in the α- and β-positions of the ethyl group and their fragment ions, particulary EtP(O)OMe + ( IV ), have been investigated both experimentally in an ion trap mass spectrometer and theoretically by electronic structure calculations at the B3LYP level. Of particular interest is the finding that the phosphonium ion IV eliminates ethene with hydrogen/deuterium loss from both the α-and β-positions. The initial step for both routes involves ethyl migration from P to O to form the ion MeOP + OEt which then loses ethene by two mechanisms, both of which lead to the same products. That…
Search forBs0→μ+μ−andB0→μ+μ−Decays with CDF II
A search has been performed for B{sub s}{sup 0} {yields} {mu}{sup +}{mu}{sup -} and B{sup 0} {yields} {mu}{sup +}{mu}{sup -} decays using 7 fb{sup -1} of integrated luminosity collected by the CDF II detector at the Fermilab Tevatron collider. The observed number of B{sup 0} candidates is consistent with background-only expectations and yields an upper limit on the branching fraction of {Beta}(B{sup 0} {yields} {mu}{sup +}{mu}{sup -}) < 6.0 x 10{sup -9} at 95% confidence level. We observe an excess of B{sub s}{sup 0} candidates. The probability that the background processes alone could produce such an excess or larger is 0.27%. The probability that the combination of background and the expe…
Measurement of thett¯production cross section inpp¯collisions ats=1.96 TeVusing soft electronb-tagging
The authors present a measurement of the t{bar t} production cross section using events with one charged lepton and jets from p{bar p} collisions at a center-of-mass energy of 1.96 TeV. A b-tagging algorithm based on the probability of displaced tracks coming from the event interaction vertex is applied to identify b quarks from top decay. Using 318 pb{sup -1} of data collected with the CDF II detector, they measure the t{bar t} production cross section in events with at least one restrictive (tight) b-tagged jet and obtain 8.9{sub -1.0}{sup +1.0}(stat.){sub -1.0}{sup +1.1}(syst.) pb. The cross section value assumes a top quark mass of m{sub t} is presented in the paper. This result is cons…
Fragmentations and reactions of some isotopically labelled dimethyl methyl phosphono and trimethyl phosphoro thiolates and thionates studied by electrospray ionisation ion trap mass spectrometry
In this paper, studies on electrospray ionisation ion trap mass spectrometry of organophosphates are extended to a series of dimethyl methylphosphono and trimethyl phosphoro thionates and thiolates and some deuterated isotopomers. Of particular, interest is the comparison of the collision-induced fragmentation of ions from these compounds with those of the non-sulphur containing analogues reported previously. The thiono and thiolo isomeric structures of the sulphur containing ions analogous to I and II (see below) have very similar energies and undergo a ready interconversion. In the case of the phosphono compounds, the electronic structure calculations show that the methyl migration implic…
Fragmentations and reactions of the organophosphate insecticide Diazinon and its oxygen analog Diazoxon studied by electrospray ionization ion trap mass spectrometry
The fragmentations and reactions of Diazinon and related compounds have been studied by electrospray ionization ion trap mass spectrometry. Several novel fragmentation and rearrangements have been observed, including an intramolecular thiono-thiolo rearrangement. The stability, in the gas-phase, of the protomers of 2-isopropyl-4-methyl-6-pyrimidinol has been demonstrated. The complexity of the gas phase ion processes observed suggest that, at present, caution Should be exercised in using this approach for the analysis of environmental and other samples until our understanding of these processes increases considerably. (J Am Soc Mass Spectrom 2005, 16, 515-523) (c) 2005 American Society for …
An ab initio and DFT study of the fragmentation and isomerisation of MeP(O)(OMe)+
The fragmentation behaviour of the ion MeP(O)OMe+ has been investigated using quantum mechanical calculations at the B3LYP and MP2 levels to support experiments made with an Ion Trap Mass Spectrometer. Two mechanisms for the loss of CH2O are found, one involving a 1,3-H migration to phosphorus and the other a 1,2-methyl migration to give P(OMe)2+ followed by a 1,3-H migration. In each case an ion-dipole complex is formed that rapidly dissociates to yield CH2O. The relative importance of each route has been previously determined experimentally via isotopic labelling experiments, and the theoretical results are found to be consistent with these experimental results. The mechanisms suggested i…