Trapped Ion Spectroscopy

Mclver R T 1970 A trapped ion analyzer cell for ion cyclotron resonance spectroscopy Rev. Sc/. Instrum. 41 555-8... 

The apparatus and techniques of ion cyclotron resonance spectroscopy have been described in detail elsewhere. Ions are formed, either by electron impact from a volatile precursor, or by laser evaporation and ionization of a solid metal target (14), and allowed to interact with neutral reactants. Freiser and co-workers have refined this experimental methodology with the use of elegant collision induced dissociation experiments for reactant preparation and the selective introduction of neutral reactants using pulsed gas valves (15). Irradiation of the ions with either lasers or conventional light sources during selected portions of the trapped ion cycle makes it possible to study ion photochemical processes... 

Infrared spectroscopy Ion trap ion mobility spectrometry Littoral combat ship Light-emitting diode... 

In order to improve the signal-to-noise ratio in collinear laser spectroscopy, an ion source with bunched beam release was tested successfully. For this purpose, the temperature of a cold trap" inside the ion source is reduced for storage of reaction products, which are released from the trap during a subsequent period of increased temperature. The release of indium was found to occur with a FWHM of approximately 0.5s, corresponding to a... 

Shockcor, J. P. Unger, S. E. Wilson, I. D. Foxall, J. P. Nicholson, J. K. Lindon, J. C. 1996. Combined HPLC, NMR spectroscopy, and ion-trap mass spectrometry with application to the detection and characterization of xenobiotic and endogenous metabolites in human urine. Anal. Chem., 68,4431 1435. 

Barinaga C. J., Eiden G. C., Alexander M. L. and Koppenaal D. W. (1996) Analytical atomic spectroscopy using ion trap devices, Fresenius J Anal Chem 355 487-493. 

Intermediates in the radiation chemistry of high polymers include ions and trapped electrons, radicals and excited states. Free radicals trapped after irradiation have been studied mainly by electron spin resonance (ESR) and in some cases by chemical methods and by ultraviolet or infrared spectroscopy. The detection of free radicals during radiolysis has been performed by pulse radiolysis and also by ESR. Trapped ions and radical-ions were characterized by absorption spectroscopy and thermoluminescence while pulse radiolysis allows their detection during irradiation. Excited states, owing to their very short lifetime, could be observed only by pulse radiolysis or by the measurement of the luminescence spectrum and decay time during steady irradiation. 

Trapped ion spectroscopy does enable tests of fundamental symmetries, such as of the equivalence principle, made for example by comparing the frequency of a Be "clock with the frequency of a hydrogen maser [26]. In another comparison of microwave atomic clocks, based on Cs and Mg, Godone et al. [27] were able to set new experimental limits on the time variation of various fundamental constants. 

Q The Spectroscopy of Ions Stored in Trapping Mass Spectrometers... 

Fluorescence spectroscopy is an alternative approach to spectroscopic characterization of trapped ions in coigunction with trapping MS. An electronically-excited ion, Af"+, is created by absorption of aUV or visible photon. Fluorescence emission, a radiative transition between the excited electronic state and ground state of the same spin state, is one pathway for de-excitation back to the ground electronic state (Equation 9.3). Other de-excitation pathways, which compete with fluorescence, are available, including internal conversion and fragmentation (PD). 

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. 

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