@article {2691,
title = {Overcoming Field Imperfections of Quadrupole Mass Filters with Mass Analysis in Islands of Stability},
journal = {Analytical Chemistry},
volume = {81},
number = {14},
year = {2009},
note = {ISI Document Delivery No.: 472MFTimes Cited: 2Cited Reference Count: 24Zhao, XianZhen Xiao, Zilan Douglas, D. J.},
month = {Jul},
pages = {5806-5811},
type = {Article},
abstract = {We have constructed, and tested as mass filters, linear quadrupoles with added hexapole fields of 4\%, 8\%, and 12\%, with and without added octopole fields. A hexapole field can be added to the field of a linear quadrupole by rotating the two y rods toward an x rod. This also adds an octopole field which can be removed by making the x rods greater in diameter than the y rods. In comparison to conventional quadrupole mass filters these rod sets have severely distorted quadrupole fields, with a mix of both even and odd higher spatial harmonics. They allow evaluating the performance of rod sets with strong geometric and field distortions as mass filters. Conventional mass analysis at the tip of the stability diagram has been compared to mass analysis using islands of stability. The stability islands are produced by applying an auxiliary quadrupole excitation field to the quadrupole. We show that with normal mass analysis at the tip of the stability diagram, the transmission, resolution, and peak shapes are relatively poor in comparison to a conventional rod set. However, the use of islands of stability dramatically improves the resolution and peak shape, and in some cases ion transmission, suggesting that mass analysis with islands of stability may provide a method to overcome a wide range of field imperfections in linear quadrupole mass filters.},
keywords = {EXCITATION, FREQUENCIES, LINEAR ION-TRAP, OCTOPOLE FIELDS, SPECTROMETRY, TRANSMISSION},
isbn = {0003-2700},
url = {://000268135000029},
author = {Zhao, X. Z. and Xiao, Z. L. and Douglas, D. J.}
}
@article {2334,
title = {Quadrupole excitation of ions in linear quadrupole ion traps with added octopole fields},
journal = {Journal of the American Society for Mass Spectrometry},
volume = {19},
number = {4},
year = {2008},
note = {ISI Document Delivery No.: 289ZDTimes Cited: 2Cited Reference Count: 24Zhao, XianZhen Granot, Ori Douglas, D. J.},
month = {Apr},
pages = {510-519},
type = {Article},
abstract = {Modeling and experimental studies of quadrupole excitation of ions in linear quadrupole traps with added octopole fields are described. An approximate solution to the equations of motion of ions trapped in a quadrupole with added octopole and dodecapole fields, with quadrupole excitation and damping is given. The solutions give the steady-state or stationary amplitudes of oscillation with different excitation frequencies. Trajectory calculations of the oscillation amplitudes are also presented. The calculations show that there can be large changes in the amplitude of ion oscillation with small changes in excitation frequency, on both the low and high-frequency sides of a resonance. Results of experiments with quadrupole excitation of reserpine ions in linear quadrupole traps with 2.0\%, 2.6\%, and 4.0\% added octopole fields are given. It is found that as the excitation frequency is changed, two resonances are generally observed, which are attributed to the motion in the x and y directions. The two resonances can have quite different intensities. Sudden jumps or sharp sided resonances are not observed, although in some cases asymmetric resonances are seen. The calculated frequency differences between the two resonances are in approximate agreement with the experiments.},
keywords = {CLOUD, fragmentation, FREQUENCIES, MASS-SPECTROMETRY, OF-FLIGHT SYSTEM, PAUL TRAP, PENNING TRAP, RESONANCES},
isbn = {1044-0305},
url = {://000255091500006},
author = {Zhao, X. Z. and Granot, O. and Douglas, D. J.}
}
@article {1386,
title = {Prediction of spectroscopic constants for diatomic molecules in the ground and excited states using time-dependent density functional theory},
journal = {Journal of Computational Chemistry},
volume = {27},
number = {2},
year = {2006},
note = {ISI Document Delivery No.: 999IGTimes Cited: 3Cited Reference Count: 52},
month = {Jan},
pages = {163-173},
type = {Article},
abstract = {Spectroscopic constants of the ground and next seven low-lying excited states of diatomic molecules CO, N-2, P-2, and ScF were computed using the density functional theory SAOP/ATZP model, in conjunction with time-dependent density functional theory (TD-DFT) and a recently developed Slater type basis set, ATZP. Spectroscopic constants, including the equilibrium distances r(e), harmonic vibrational frequency omega(e), vibrational anharmonicity omega(e)x(e), rotational constant B-e, centrifugal distortion constant D-e, the vibration-rotation interaction constant alpha(e), and the vibrational zero-point energy E-n(0), were generated in an effort to establish a reliable database for electron spectroscopy. By comparison with experimental values and a similar model with an established larger Slater-type basis set, et-QZ3P-xD, it was found that this model provides reliably accurate results at reduced computational costs, for both the ground and excited states of the molecules. The over all errors of all eight lowest lying electronic states of the molecules under study using the effective basis set are r(e)(+/- 4\%), omega(e)(+/- 5\% mostly without exceeding +/- 20\%), omega(e)x(e)(+/- 5\% mostly without exceeding 20\%, much more accurate than a previous study on this constant of +/- 30\%), B-e(+/- 8\%), D-e(+/- 10\%), alpha(e)(+/- 10\%), and E-n(0)(+/- 10\%). The accuracy obtained using the ATZP basis set is very competitive to the larger et-QZ3P-xD basis set in particular in the ground electronic states. The overall errors in r(e), omega(e)x(e) and alpha(e) in the ground states were given by +/- 0.7, +/- 10.1, and +/- 8.4\%, respectively, using the efficient ATZP basis set, which is competitive to the errors of +/- 0.5, +/- 9.2, and +/- 9.1\%, respectively for those constants using the larger et-QZ3P-xD basis set. The latter basis set, however, needs approximately four times of the CPU time on the National Supercomputing Facilities (Australia). Due to the efficiency of the model (TD-DFT, SAOP and ATZP), it will be readily applied to study larger molecular systems. (c) 2005 Wiley Periodicals, Inc.},
keywords = {Density Function Theroy, diatomic molecules, DIPOLE-MOMENT, ELECTRONIC-STRUCTURE, emission, EXCITATION-ENERGIES, excited, FREQUENCIES, GAUSSIAN-BASIS SETS, ground state, INDUCED POLARIZATION FUNCTIONS, ORBITALS, POTENTIALS, SPECTRA, spectroscopic constants, STATES, SURFACES},
isbn = {0192-8651},
url = {://000234382400005},
author = {Falzon, C. T. and Chong, D. P. and Wang, F.}
}
@article {4935,
title = {The electronic spectrum of silicon methylidyne (SiCH), a molecule with a silicon-carbon triple bond in the excited state},
journal = {Journal of Chemical Physics},
volume = {112},
number = {8},
year = {2000},
note = {ISI Document Delivery No.: 284RDTimes Cited: 22Cited Reference Count: 56},
month = {Feb},
pages = {3662-3670},
type = {Article},
abstract = {The (A) over tilde (2)Sigma(+)-X (2)Pi(i) transition of jet-cooled silicon methylidyne, SiCH, has been recorded by laser-induced fluorescence in the 850-600 nm region. The radical was produced in an electric discharge using tetramethylsilane as the precursor. Fifteen cold bands of SiCH and 16 bands of SiCD have been assigned vibrationally, giving the upper state frequencies as v(2)({\textquoteright})=715/558 cm(-1) and v(3)({\textquoteright})=1168/1127 cm(-1) for SiCH/SiCD. Rotational analysis of the 0(0)(0) and 3(0)(3) bands for each isotopomer has given the following molecular structures: r(0)({\textquoteright})(Si-C)=1.692 52(8), r(0)({\textquoteright})(C-H)=1.0677(4), r(0)({\textquoteright})(Si-C)=1.6118(1), and r(0)({\textquoteright})(C-H)=1.0625(5) Angstrom. The silicon-carbon bond length in the X (2)Pi ground state of SiCH (electron configuration ...sigma(2)pi(3)) is typical for a Si=C double bond; in the (A) over tilde (2)Sigma(+) excited state (...sigma(1)pi(4)) it corresponds to a triple bond. This work provides the first experimental measurement of the length of the carbon-silicon triple bond. (C) 2000 American Institute of Physics. [S0021-9606(00)00508-0].},
keywords = {DISCHARGE JET SPECTROSCOPY, FREQUENCIES, GAS-PHASE, GEOMETRY, laser spectroscopy, MONOFLUOROSILYLENE, ROTATIONAL ANALYSIS, SIMPLEST UNSATURATED SILYLENE, SYSTEM, TRANSITION, vibrational},
isbn = {0021-9606},
url = {://000085345300022},
author = {Smith, T. C. and Li, H. Y. and Clouthier, D. J. and Kingston, C. T. and Merer, A. J.}
}
@article {4787,
title = {Peak structure with a quadrupole mass filter operated in the third stability region},
journal = {International Journal of Mass Spectrometry},
volume = {197},
year = {2000},
note = {ISI Document Delivery No.: 291DFTimes Cited: 6Cited Reference Count: 11Sp. Iss. SI},
month = {Feb},
pages = {113-121},
type = {Article},
abstract = {Peak structure for a quadrupole operated in the third stability region with Mathieu parameters (a, q) approximate to (3, 3) has been studied experimentally and modeled theoretically. It is shown that the structure is due to the imaging properties of the quadrupole field which are caused by the wavelike properties of the ion trajectories. Ions enter the quadrupole through a small inlet aperture on axis. When ions are focused on the center of the exit aperture the transmission is a maximum. Conversely when ions have trajectories that place them near the rods at the exit aperture the transmission is a minimum and a dip appears on a peak. The positions of dips on a peak can be assigned to lines in the stability diagram. These lines follow iso-beta lines, where beta is the parameter that determines the frequencies of ion motion. The positions of the lines are controlled by the number of rf cycles, which ions spend in the quadrupole field. At high resolution (>300) and low ion axial energy (<20 eV) the peak splitting is minimal or absent. (C) 2000 Elsevier Science B.V.},
keywords = {FREQUENCIES, ION-TRAP, peak, peak shape, quadrupole mass filter, STRUCTURE, third stability region},
isbn = {1387-3806},
url = {://000085718300007},
author = {Du, Z. H. and Douglas, D. J. and Glebova, T. and Konenkov, N. V.}
}