Mass-selected ions, optical spectroscopy

Note The acronyms used here are OSPED (optical spectroscopy in a pulsed electrical discharge), FAMS (flowing afterglow mass spectrometry), SIFT (selected ion flow tube), TRAPI (time-resolved atmospheric pressure ionization mass spectrometry), PHPMS (pulsed high-pressure ionization mass spectrometry), ICRMS (ion cyclotron resonance mass spectrometry), and ADO (averaged dipole orientation collision rate theory). 

Fig. 1.5. Experimental setup of the high-frequency laser vaporization cluster ion source driven by a 100-Hz Nd Yag laser for the production of ion clusters, ion optics with a quadrupole deflector, and quadrupole mass Alter for size-selection and deposition the analysis chamber with a mass spectrometer for thermal desorption spectroscopy (TDS), a Fourier transform infrared spectrometer, a spherical electron energy analyzer for Auger electron spectroscopy (AES) for in situ characterization of the clusters [73]...

The past decade has seen an explosion in investigations of molecular ions using a variety of optical spectroscopic techniques in conjunction with trapping mass spectrometers. The mass selection and ion storage capabilities of instruments such as 3-D QITs and FT-ICR mass spectrometers provide valuable control over the ion population under investigation. Moreover, thanks to modem ion sources, the size of molecules is no longer a limitation for gas-phase ion spectroscopic studies. A number of spectroscopic techniques have been developed to probe gas-phase molecules that will be fruitful when applied to the spectroscopy of trapped ions. 

Wang, Y. Hendrickson, C.L. Marshall, A.G. Direct optical spectroscopy of gas-phase molecular ions trapped and mass-selected by ion cyclotron resonance Laser-induced fluorescence excitation spectrum of hexafluorobenzene (C F ). J. Chem.Phys. Lett. 2001,334, 69-75. 

Inductively Coupled Plasma. Atomic Fluorescence Spectrometry. Atomic Mass Spectrometry Inductively Coupled Plasma. Chemiluminescence Liquid-Phase. Enzymes Enzyme-Based Electrodes. Fluorescence Instrumentation. Ion-Selective Electrodes Overview. Optical Spectroscopy Detection Devices. Sensors Overview. Voltammetry Overview. 

The most common RF ion trap is a Paul trap [42], a 3-D quadrupole device in which ions are confined in a small volume of typically a few tens of millimeters [2] between a hyqterbolically shaped inner surface of a ring electrode and two end-cap electrodes, also of hyperbolic shape (Fig. 1). Elach end-cap electrode has a central hole for loading and ejection of irais. As these traps are compact, commercially available, and allow mass-selection of stored ions, they have become an increasingly popular technically simple solution for cryogenic ion spectroscopy. Paul traps have several drawbacks for cold-ion spectroscopy, however inefficient ion injection an intrinsically limited ability to cool ions low storage volume and inconvenient optical access to the ions by laser beams. 

In both total and sequential dissolutions, the result is a solution containing the components of rocks and soils. This solution is then analyzed by different methods. Mostly, spectroscopic methods are used atomic absorption and emission spectroscopic methods, ultraviolet, atom fluorescence, and x-ray fluorescence spectrometry. Multielement methods (e.g., inductively coupled plasma optical emission spectroscopy) obviously have some advantages. Moreover, elec-troanalytical methods, ion-selective electrodes, and neutron activation analysis can also be applied. Spectroscopic methods can also be combined with mass spectrometry. 

The most utilized methods include X-ray fluorescence (XRF), atomic absorption spectroscopy (AAS), activation analysis (AA), optical emission spectroscopy (OES) and inductively coupled plasma (ICP), mass spectroscopy (MS). Less frequently used techniques include ion-selective electrode (ISE), proton induced X-ray emission (PIXE), and ion chromatography (IC). In different laboratories each of these methods may be practiced by using one of several optional approaches or techniques. For instance, activation analysis may involve conventional thermal neutron activation analyses, fast neutron activation analysis, photon activation analysis, prompt gamma activation analysis, or activation analysis with radio chemical separations. X-ray fluorescence options include both wave-length and/or energy dispersive techniques. Atomic absorption spectroscopy options include both conventional flame and flameless graphite tube techniques. 

Because of a low number density of cluster ions isolated in the gas phase, conventional methodologies available for condensed matters are not applicable to the measurements of the cluster properties. The first step of the measurements is to obtain a cluster ion with a desired size by mass-spectroscopic separation of cluster ions in a cluster source. After the size-selection, the number density of the size-selected cluster ion is typically 10 cm or lower, which is too low for the conventional optical absorption spectroscopy, for instance. In the measurement of an electronic conductivity, one should attach electrodes to the specimen that you intend to measure. 

Optical microscopy (OM), polarized light microscopy (PLM), phase contrast microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and scanning transmission electron microscopy (STEM) are the methods normally used for identification and quantification of the trace amounts of asbestos fibers that are encountered in the environment and lung tissue. Energy-dispersive X-ray spectrometry (EDXS) is used in both SEM and TEM for chemical analysis of individual particles, while selected-area electron diffraction (SAED) pattern analysis in TEM can provide details of the cell unit of individual particles of mass down to 10 g. It helps to differentiate between antigorite and chrysotile. Secondary ion mass spectrometry, laser microprobe mass spectrometry (EMMS), electron probe X-ray microanalysis (EPXMA), and X-ray photoelectron spectroscopy (XPS) are also analytical techniques used for asbestos chemical characterization. 

Figure 1.13 Selected analytical techniques used for metallomics studies. ICP-OES, inductively coupled plasma optical emission spectroscopy, ICP-MS, inductively coupled plasma mass spectrometry LA-ICP-MS, laser ablation ICP-MS XRF, X-ray fluorescence spectroscopy PIXE, proton induced X-ray emission NAA, neutron activation analysis SIMS, secondary ion mass spectroscopy GE, gel electrophoresis LC, liquid chromatography GC, gas chromatography MS, mass spectrometry, which includes MALDI-TOF-MS, matrix-assisted laser desorption/ ionization time of flight mass spectrometry and ESI-MS, electron spray ionization mass spectrometry NMR, nuclear magnetic resonance PX, protein crystallography XAS, X-ray absorption spectroscopy NS, neutron scattering.

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