Search results for "Ion trap"
showing 10 items of 246 documents
Chemisorption of hydrogen on a V5+ cluster
1996
Abstract The binding between V 5 + and hydrogen is studied by collision induced dissociation of the cluster-adsorbate V 5 + H 2 . Vanadium clusters are produced by laser vaporization and injected into an electromagnetic ion trap. After mass separation of V 5 + , the pulsed addition of hydrogen yields V 5 + H 2 . The desorption of hydrogen is studied by acceleration of V 5 + H 2 with variable rf voltages and collisions with argon atoms. From the threshold voltage necessary for dissociation a binding energy of H 2 on V 5 + of 2.4 ± 0.3 eV is estimated. This value is consistent with a dissociative chemisorption of hydrogen.
Collisional relaxation measurements on Pb+ hyperfine levels
1993
The time constants for population relaxation of optically pumped Pb+ ions in a Paul ion trap have been determined in a He buffer gas atmosphere with additional components of other gases. For the 6P1/2 ground state of Pb+ and an ion temperatur of 104 K we find cross sections of 0.72(0.33)·10−17 cm2; 0.59(0.38)·10−15 cm2; and 2.56(0.74)·10−14 cm2 for He, N2 and O2, respectively. The error includes an estimated 20% uncertaincy in the pressure calibration of a residual gas analyser.
Characterization of methyl orange and its photocatalytic degradation products by HPLC/UV–VIS diode array and atmospheric pressure ionization quadrupo…
2002
Abstract HPLC/UV–VIS diode array and HPLC/MS techniques were successfully applied to the analysis of sulfonated molecules present in samples coming from the photocatalytic degradation of the azo dye indicator, methyl orange. The substrate was chosen as a simple model for the study of reactions involving the more complex commercial products used for the dyeing of textile fibers. Unexpected MS fragmentation path was observed, due to the very stable methyl orange molecular structure. The chromatographic information were combined with the obtained MS, MS/MS data and the UV–VIS diode array spectra and allowed to rationalize the molecular structures attributable to the various degradation product…
Analysis of pesticides in fruits by pressurized liquid extraction and liquid chromatography-ion trap-triple stage mass spectrometry.
2005
A multi-residue method using pressurized liquid extraction (PLE) and liquid chromatography-quadrupole ion trap-triple stage mass spectrometry (LC-IT-MS(3)) has been developed for determining trace levels of pesticides in fruits. The selected pesticides can be distinguished in: benzimidazoles and azoles, organophosphorus, carbamates, neonicotinoids, and acaricides. PLE has been optimized to extract these pesticide residues from oranges and peaches by studying the effect of experimental variables on PLE efficiency. Samples were extracted at high temperature and pressure (75 degrees C and 1500psi) using ethyl acetate as extraction solvent and acidic alumina as drying agent. The recoveries obta…
Analysis of Organic Aerosols Using a Micro-Orifice Volatilization Impactor Coupled to an Atmospheric-Pressure Chemical Ionization Mass Spectrometer
2014
We present the development and characterization of a combination of a micro-orifice volatilization impactor (MOVI) and an ion trap mass spectrometer (IT/MS) with an atmospheric-pressure chemical ionization (APCI) source. The MOVI is a multi-jet impactor with 100 nozzles, allowing the collection of aerosol particles by inertial impaction on a deposition plate. The pressure drop behind the nozzles is approximately 5%, resulting in a pressure of 96 kPa on the collection surface for ambient pressures of 101.3 kPa. The cut-point diameter (diameter of 50% collection efficiency) is at 0.13 μm for a sampling flow rate of 10 L min–1. After the collection step, aerosol particles are evaporated by he…
Determination of carbosulfan and its metabolites in oranges by liquid chromatography ion-trap triple-stage mass spectrometry.
2005
Liquid chromatography ion-trap mass spectrometry LC-MSn has been successfully applied to identify and confirm carbosulfan and seven of its metabolites in oranges after pressurized liquid extraction (PLE) with dichloromethane. Mass spectra of carbosulfan and its metabolites were investigated using multiple stages of mass spectrometry. Although interpretation of the fragmentation pathways, based on mass spectra, enables structural elucidation and identification of these compounds, the proposed fragmentation pathways and ion structures need verification by exact mass measurements. The analytical method--PLE and LC-MS3 --was validated: limits of quantification (LOQ) ranged from 0.01 to 0.07 mg …
The Ramsey method in high-precision mass spectrometry with Penning traps: Experimental results
2007
The highest precision in direct mass measurements is obtained with Penning trap mass spectrometry. Most experiments use the interconversion of the magnetron and cyclotron motional modes of the stored ion due to excitation by external radiofrequency-quadrupole fields. In this work a new excitation scheme, Ramsey's method of time-separated oscillatory fields, has been successfully tested. It has been shown to reduce significantly the uncertainty in the determination of the cyclotron frequency and thus of the ion mass of interest. The theoretical description of the ion motion excited with Ramsey's method in a Penning trap and subsequently the calculation of the resonance line shapes for differ…
Theory of simultaneous dipole and quadrupole excitation of the ion motion in a Penning trap
2012
Abstract Penning traps confine ions of atoms and molecules as well as other charged particles by a combination of static electric and magnetic fields to the central region of the trap, where these objects can be studied. Most experiments employ pulses of dipolar radio-frequency radiation followed by pulses of quadrupolar radio-frequency radiation to manipulate the motional state of the trapped particles. Instead of a sequential procedure an excitation of the ion motion by the simultaneous application of dipolar and quadrupolar rf-fields is also conceivable. This paper investigates the theory of simultaneous excitation under very general assumptions, with inclusion of possible damping terms.…
Quadrupole excitation of stored ion motion at the true cyclotron frequency
1995
Abstract The motion of an ion in a Penning trap has been investigated in the presence of an azimuthal quadrupole radio frequency field and a damping force provided by buffer gas collisions. Analytical expressions are derived which describe the line shape of the cyclotron resonance as well as the properties of the mass-selective cooling mechanism for heavy ions. Excellent agreement is observed between theoretical results and experimental data obtained with the tandem Penning trap mass spectromer ISOLTRAP at ISOLDE (CERN).
The elliptical Penning trap: Experimental investigations and simulations
2008
Abstract The application of an additional azimuthal quadrupolar electrostatic field to a Penning trap leads to a field configuration referred to as an elliptical Penning trap. The resulting changes of the radial ion motions have been investigated experimentally and by use of simulations. The eigenfrequencies, i.e., the magnetron frequency ω ˜ − and the reduced cyclotron frequency ω ˜ + , are found to be shifted with respect to those of the standard Penning trap ω − , ω + , respectively. As the shift of the magnetron frequency ω ˜ − is larger than that of the reduced cyclotron frequency ω ˜ + their sum ω ˜ + + ω ˜ − is also a function of the ellipticity and no longer equal to the cyclotron f…