@article {604,
	title = {Quadrupole mass filters with octopole fields},
	journal = {Rapid Communications in Mass Spectrometry},
	volume = {17},
	number = {22},
	year = {2003},
	note = {ISI Document Delivery No.: 742BLTimes Cited: 16Cited Reference Count: 23},
	pages = {2495-2502},
	type = {Article},
	abstract = {The performance of quadrupole mass filters with added octopole fields in the range 2.0-4.0\% has been investigated. The added fields are much greater than those normally added to conventional rod sets by mechanical tolerances or construction errors. Quadrupole rod sets with added octopole fields were constructed with round rods by making one pair of rods greater in diameter than the other pair. For positive ions, resolution at half height of only about 200 is possible if the negative direct current (dc) output of the quadrupole power supply is connected to the smaller rods. If the positive dc output of the quadrupole power supply is connected to the smaller rods, the resolution improves dramatically; a resolution at half height of 5800 has been observed with a rod set with 2.6\% added octopole field. For negative ions the best resolution is obtained with the polarity of the dc reversed, i.e. with the negative dc applied to the smaller rods. These findings are unexpected in view of the literature that argues that to obtain high mass resolution with quadrupole mass filters, higher order multipoles must be kept as small as possible. Numerical simulations of peak shapes agree qualitatively with experiments. Simulation of the boundaries of the first stability region for positive ions shows that when the positive dc is applied to the smaller rods, the addition of a 2.0\% octopole field causes the boundaries to shift slightly but the boundaries are well defined, and the tip of the stability region remains sharp. When the positive dc is applied to the larger rods, the boundaries of the stability region move out and become diffuse. For instruments that require a rod set that can be used both as a linear trap and a mass filter, these rod sets may offer improved trap performance while still being capable of providing conventional mass analysis. Copyright (C) 2003 John Wiley Sons, Ltd.},
	keywords = {ELECTRODES, LINEAR ION-TRAP, OF-FLIGHT SYSTEM, PERFORMANCE, SPATIAL HARMONICS, SPECTROMETER},
	isbn = {0951-4198},
	url = {<Go to ISI>://000186495300007},
	author = {Ding, C. F. and Konenkov, N. V. and Douglas, D. J.}
}
@article {4528,
	title = {Elemental analysis with quadrupole mass filters operated in higher stability regions},
	journal = {Journal of Analytical Atomic Spectrometry},
	volume = {14},
	number = {8},
	year = {1999},
	note = {ISI Document Delivery No.: 229LPTimes Cited: 23Cited Reference Count: 47},
	month = {Aug},
	pages = {1111-1119},
	type = {Article},
	abstract = {Operation of quadrupole mass filters in higher zones of stability is described with an emphasis on the potential for elemental mass spectrometry. The higher zones allow a resolution at half height of up to 9000 on atomic ions and make possible unit resolution on ions with kinetic energies up to several thousand electron volts. The theory of quadrupole operation is briefly reviewed. Operation of quadrupoles in the third stability region with Mathieu parameters (a,q)approximate to(3,3) and the second stability region with (a,q)approximate to(0.02, 7.55) is described in detail. Previously unpublished data showing the variation of resolution with ion energy are presented. The variation of transmission with resolution is compared with previous calculations and with new calculations presented here.},
	keywords = {2ND, ANALYZER, ATMOSPHERE, DIAGRAM, HELIUM, HIGH-RESOLUTION, ICP-MS, SEPARATION MODE, SPECTROMETER, ZONE},
	isbn = {0267-9477},
	url = {<Go to ISI>://000082196300002},
	author = {Du, Z. H. and Douglas, D. J. and Konenkov, N.}
}
@article {4246,
	title = {Ion source emittance influence on the transmission of a quadrupole operated in the second stability region},
	journal = {Journal of the American Society for Mass Spectrometry},
	volume = {9},
	number = {10},
	year = {1998},
	note = {ISI Document Delivery No.: 121NBTimes Cited: 6Cited Reference Count: 19},
	month = {Oct},
	pages = {1074-1080},
	type = {Article},
	abstract = {The variation of transmission (T) with resolution (R) has been calculated for a quadrupole mass filter operated in the second stability region with Mathieu parameters q = 7.547 and a = 0 to 0.02995. The fringing fields at the entrance to the quadrupole, which can be strongly defocusing, and which can dramatically reduce the acceptance, have been included in the calculation. Even in the absence of fringing fields, at a resolution of 10,000 the acceptance in the x and y directions is less than 2 x 10(-4) pi r(0)(4) f(2) which is about 10(-3) of the acceptance in the first stability region at low resolution. Because the source emittance can strongly effect the T(R) behavior, the calculation of ion transmission has been done for two source emittances that correspond to different degrees of focusing of ions into the quadrupole. The T(R) characteristics for two realistic source emittances give behavior markedly different from the decrease in acceptance with increasing resolution which previously has been used as a measure of the quadrupole transmission. Comparisons of the calculated transmission losses with increasing resolution to earlier experimental results obtained with an inductively coupled plasma source show good agreement provided an emittance which corresponds to ions being tightly focused into the quadrupole is used. The calculation demonstrates that up to a resolution at half height of 7000 in the experiment, the transmission losses were a result of the decreasing quadrupole acceptance. At higher resolution the experimental transmission was limited by either the residence time of the ions in the quadrupole or the rod quality. It is also shown that the strong defocusing effects of the fringing fields at the entrance of the quadrupole can be largely overcome by accelerating the ions through these fields and then decelerating the ions in the quadrupole. (C) 1998 American Society for Mass Spectrometry.},
	keywords = {ANALYZER, mass filter, SEPARATION MODE, SPECTROMETER},
	isbn = {1044-0305},
	url = {<Go to ISI>://000076019000011},
	author = {Douglas, D. J. and Konenkov, N. V.}
}
@article {4295,
	title = {Microwave spectra of the Ne-N-2 van der Waals complex: Experiment and theory},
	journal = {Journal of Chemical Physics},
	volume = {109},
	number = {13},
	year = {1998},
	note = {ISI Document Delivery No.: 123YFTimes Cited: 15Cited Reference Count: 29},
	month = {Oct},
	pages = {5420-5432},
	type = {Article},
	abstract = {High-resolution microwave spectra of the ground state Ne-20-N-14(2), Ne-20-N-15(2), Ne-22-N-14(2), and Ne-22-N-15(2) Van der Waals complexes, involving rotational levels up to J=4, are reported. Interpretation and assignment of the observed transitions were made by combining results of measurements and theoretical predictions of the MW line positions in terms of available empirical potential energy surfaces and of a new high-level ab initio potential energy surface. The deviations of the calculated MW spectra from those observed experimentally are more uniform for the ab initio potential surface than they are for the empirical potential surfaces, allowing for reduction of the deviations to within 0.07\% for all isotopomers by a single-parameter scaling of the nb initio potential energy surface. The scaled Ne-N-2 interaction potential was used to predict the MW line positions for the transitions J{\textquoteright}-J "=3-2, 4-3 for all species. A simple procedure is proposed to improve the ab initio results for atom-diatom systems on the basis of atom-atom interaction components. (C) 1998 American Institute of Physics. [S0021-9606(98)01437-8].},
	keywords = {AXES, BASIS-SETS, COEFFICIENTS, CONSTANTS, MOLECULES, N2-AR, POTENTIAL-ENERGY SURFACE, SPECTROMETER, WAVE-FUNCTIONS},
	isbn = {0021-9606},
	url = {<Go to ISI>://000076152700030},
	author = {Jager, W. and Xu, Y. and Armstrong, G. and Gerry, M. C. L. and Naumkin, F. Y. and Wang, F. and McCourt, F. R. W.}
}
@article {3995,
	title = {Fourier-transform microwave spectroscopy of InF, InCl, and InBr, prepared using laser ablation},
	journal = {Journal of the Chemical Society-Faraday Transactions},
	volume = {93},
	number = {6},
	year = {1997},
	note = {ISI Document Delivery No.: WQ180Times Cited: 10Cited Reference Count: 43},
	month = {Mar},
	pages = {1053-1059},
	type = {Article},
	abstract = {High-resolution rotational spectra of InF, InCl, and InBr have been measured with a pulsed jet cavity Fourier-transform microwave spectrometer. Samples were prepared by vaporizing In with a pulsed Nd:YAG laser, and reacting the vapour with a precursor gas entrained in the Ne backing gas of the jet. Precise rotational and nuclear quadrupole coupling constants have been obtained for all these molecules, along with the first nuclear spin-rotation constants of InCl and InBr. The hyperfine coupling constants are discussed in terms of the electronic structures of the molecules.},
	keywords = {CONSTANTS, MONOFLUORIDE, PARAMETERS, PURE ROTATIONAL SPECTRUM, SPECTROMETER, STATES},
	isbn = {0956-5000},
	url = {<Go to ISI>://A1997WQ18000005},
	author = {Hensel, K. D. and Gerry, M. C. L.}
}
@article {4109,
	title = {Fourier-transform microwave spectrum, structure, harmonic force field, and hyperfine constants of sulfur chloride fluoride, ClSF},
	journal = {Journal of Chemical Physics},
	volume = {106},
	number = {24},
	year = {1997},
	note = {ISI Document Delivery No.: XE593Times Cited: 3Cited Reference Count: 46},
	month = {Jun},
	pages = {10037-10047},
	type = {Article},
	abstract = {The rotational spectrum of sulfur choride fluoride, ClSF, has been observed for the first time in the frequency range 8-26 GHz by means of a pulsed molecular jet Fourier-transform microwave spectrometer. The unstable sample molecule has been prepared using a pulsed electrical discharge in jets containing a mixture of SF6 and SCl2 in Ne. Besides the parent species (ClSF)-Cl-35-S-32-F-19, the isotopomers (ClSF)-Cl-37-S-32-F-19 and (ClSF)-Cl-35-S-34-F-19 could be observed in natural abundance. Rotational constants and quartic centrifugal distortion constants as well as nuclear quadrupole coupling constants due to Cl-35 and Cl-37 and spin-rotation constants due to Cl-35, Cl-37, and F-19 are given. The data were used for the determination of r(0), r(Delta P), r(s) structural parameters. Additionally, the new data were used for the refinement of the molecular harmonic force field. Results from those harmonic force field calculations were applied in the evaluation of the ground-state average structure, r(z), and the estimation of the equilibrium structure, r(e). The r(s) structure is r(SF)=160.653(162) pm, r(SCl)=199.437(65) pm, and angle(ClSF)=100.732(81)degrees. The diagonal elements of the Cl-35/Cl-37 quadrupole coupling tensors have been obtained, and are interpreted in terms of the bonding at Cl-35/Cl-37. Negative F-19 spin-rotation constants suggest a close analogy of the electronic structures of CISF and SF2. (C) 1997 American Institute of Physics.},
	keywords = {(SF2)-S-32, DICHLORIDE, DIFLUORIDE, DIODE-LASER SPECTROSCOPY, F-19 SPIN, MONOFLUORIDE, POTENTIAL FUNCTION, QUADRUPOLE COUPLING-CONSTANTS, ROTATION, SCL2, SPECTROMETER},
	isbn = {0021-9606},
	url = {<Go to ISI>://A1997XE59300006},
	author = {Preusser, J. and Gerry, M. C. L.}
}
@article {4146,
	title = {Investigation of the pure rotational spectrum of magnesium monobromide by Fourier transform microwave spectroscopy},
	journal = {Journal of Chemical Physics},
	volume = {107},
	number = {23},
	year = {1997},
	note = {ISI Document Delivery No.: YK982Times Cited: 7Cited Reference Count: 39},
	month = {Dec},
	pages = {9835-9841},
	type = {Article},
	abstract = {The pure rotational spectrum of the free radical MgBr has been measured in its (2) Sigma(+) ground electronic state by Fourier transform microwave spectroscopy. Transitions have been observed for both (MgBr)-Mg-24-Br-79 and (MgBr)-Mg-24-Br-81 in the v = 0 and v = 1 vibrational states. Rotational and centrifugal distortion constants have been determined for each isotopomer in each vibrational state. Equilibrium rotational constants have been calculated and an accurate equilibrium bond length has been determined. Spin-rotation constants, for both the unpaired electron and the bromine nuclei, have been calculated along with magnetic and nuclear quadrupole hyperfine constants for the bromine nuclei. From these constants, the electronic structure of MgBr has been investigated and comparisons have been made to similar compounds. The unpaired electron spin density on the bromine nucleus has been found to be very small, suggesting that this is a very ionic compound. However, the Mg-Br bond has been found to have more covalent character than the bond in other alkaline earth monobromides. (C) 1997 American Institute of Physics. [S0021-9606(97)02046-1].},
	keywords = {BAF, CABR, HYPERFINE-STRUCTURE, MGF, MILLIMETER-WAVE SPECTRUM, MOLECULAR-BEAM, PARAMETERS, radicals, RF DOUBLE-RESONANCE, SPECTROMETER},
	isbn = {0021-9606},
	url = {<Go to ISI>://A1997YK98200014},
	author = {Walker, K. A. and Gerry, M. C. L.}
}
@article {4147,
	title = {Nuclear hyperfine interactions in the microwave spectrum of aluminium isocyanide},
	journal = {Chemical Physics Letters},
	volume = {278},
	number = {1-3},
	year = {1997},
	note = {ISI Document Delivery No.: YF643Times Cited: 23Cited Reference Count: 34},
	month = {Oct},
	pages = {9-15},
	type = {Article},
	abstract = {The pure rotational spectrum of AINC has been measured between 11.9 and 24.0 GHz using a pulsed jet Fourier transform microwave spectrometer. The molecule was produced using a laser ablation source, in which the ablated Al metal reacted with cyanogen present in the Ar backing gas of the jet. Hyperfine structure due to both the Al-27 and N-14 nuclei has been observed. Nuclear quadrupole coupling constants and nuclear spin-rotation constants have been determined for both nuclei along with an Al-N nuclear spin-spin coupling constant. The electronic structure of AINC has been investigated by estimating the degree of sp-hybridisation of the Al and N bonding orbitals. Comparisons have been made to similar linear metal isocyanide and aluminium halide species. (C) 1997 Elsevier Science B.V.},
	keywords = {ABINITIO, ALCL, interactions, IRC+10216, MG-BEARING MOLECULE, MILLIMETER, PREDICTION, ROTATIONAL SPECTRUM, SPECTROMETER, spectroscopic constants, SPIN},
	isbn = {0009-2614},
	url = {<Go to ISI>://A1997YF64300002},
	author = {Walker, K. A. and Gerry, M. C. L.}
}
@article {3937,
	title = {Rotational spectra of selected isotopic species of vinyl cyanide: Molecular structure and quadrupole hyperfine structure},
	journal = {Journal of Molecular Spectroscopy},
	volume = {181},
	number = {2},
	year = {1997},
	note = {ISI Document Delivery No.: WH318Times Cited: 11Cited Reference Count: 27},
	month = {Feb},
	pages = {330-344},
	type = {Article},
	abstract = {{The pure rotational spectra of 13 isotopically substituted forms of vinyl cyanide},
	keywords = {ACRYLONITRILE, CENTRIFUGAL-DISTORTION CONSTANTS, MOMENTS, PARAMETERS, SPECTROMETER, SPECTROSCOPY},
	isbn = {0022-2852},
	url = {<Go to ISI>://A1997WH31800010},
	author = {Colmont, J. M. and Wlodarczak, G. and Priem, D. and Muller, H. S. P. and Tien, E. H. and Richards, R. J. and Gerry, M. C. L.}
}
@article {3774,
	title = {Microwave Fourier transform spectroscopy of perchloryl fluoride: (FClO3)-F-19-Cl-35/37-O-16 and (FClO2O)-F-19-Cl-35/37-O-16-O-18},
	journal = {Journal of Molecular Spectroscopy},
	volume = {175},
	number = {1},
	year = {1996},
	note = {ISI Document Delivery No.: TX208Times Cited: 18Cited Reference Count: 81},
	month = {Jan},
	pages = {120-132},
	type = {Article},
	abstract = {O-18-enriched, monolabeled perchloryl fluoride, (FClO2O)-F-19-Cl-35/37-O-16-O-18, has been synthesized. Its rotational spectrum has been studied in the 4-22 GHz region. In addition, the spectra of the symmetric isotopomers (FClO3)-F-19-Cl-35/37-O-16 have been reinvestigated. Rotational and centrifugal distortion constants, as well as chlorine nuclear quadrupole and chlorine and fluorine spin-rotation and spin-spin coupling constants, have been determined for the ground vibrational state. The ground state rotational data have been used to evaluate geometrical parameters. The harmonic force field has been refined. The results are compared with data of related molecules. (C) 1996 Academic Press. Inc.},
	keywords = {BANDS, BOND LENGTHS, COUPLING-CONSTANTS, FCLO3, FORCE-CONSTANTS, N-F, NU-2, ROTATIONAL SPECTRUM, SPECTROMETER, STATES},
	isbn = {0022-2852},
	url = {<Go to ISI>://A1996TX20800017},
	author = {Muller, H. S. P. and Gerry, M. C. L.}
}
@article {3368,
	title = {MICROWAVE MILLIMETER-WAVE DOUBLE-RESONANCE EXPERIMENTS ON AR-CO},
	journal = {Journal of Chemical Physics},
	volume = {102},
	number = {9},
	year = {1995},
	note = {ISI Document Delivery No.: QH968Times Cited: 35Cited Reference Count: 27},
	month = {Mar},
	pages = {3587-3592},
	type = {Article},
	keywords = {CARBON-MONOXIDE, FOURIER-TRANSFORM SPECTROSCOPY, PULSED MOLECULAR-BEAM, RADIOFREQUENCY, RANGE, SPECTROMETER},
	isbn = {0021-9606},
	url = {<Go to ISI>://A1995QH96800008},
	author = {Jager, W. and Gerry, M. C. L.}
}
@article {2834,
	title = {PURE ROTATIONAL SPECTRA OF THE MIXED RARE-GAS VAN-DER-WAALS COMPLEXES NE-XE, AR-XE, AND KR-XE},
	journal = {Journal of Chemical Physics},
	volume = {99},
	number = {2},
	year = {1993},
	note = {ISI Document Delivery No.: LM894Times Cited: 48Cited Reference Count: 50},
	month = {Jul},
	pages = {919-927},
	type = {Article},
	abstract = {Pure rotational transitions in the vibrational ground states of various isotopomers of the heteronuclear rare gas dimers Ne-Xe, Ar-Xe, and Kr-Xe have been measured using a pulsed molecular beam cavity microwave Fourier transform spectrometer. Rotational and centrifugal distortion constants have been obtained, and have yielded estimates of the lengths of the van der Waals bonds and of their harmonic vibration frequencies. Effects due to nuclear quadrupole coupling have been observed in Xe-131-containing complexes and have yielded the corresponding nuclear quadrupole coupling constants. The electric molecular dipole moments of the complexes have been estimated from the excitation pulse lengths, optimized for maximum signal strength (pi/2 condition).},
	keywords = {ARGON, CONSTANTS, curve, DIPOLE-MOMENTS, EXCITED-STATES, INTERATOMIC POTENTIALS, PAIRS, SPECTROMETER, TRANSFORM MICROWAVE SPECTROSCOPY, ULTRAVIOLET-LASER SPECTROSCOPY},
	isbn = {0021-9606},
	url = {<Go to ISI>://A1993LM89400017},
	author = {Jager, W. and Xu, Y. J. and Gerry, M. C. L.}
}
