Resonance collision-induced

Somogyi, A. Probing Peptide Fragment Ion Structures by Combining Sustained Off-Resonance Collision-Induced Dissociation and Gas-Phase H/D Exchange (SORI-HDX) in Fourier Transform Ion-Cyclotron Resonance (FT-ICR) Instruments. J. Am. Soc. Mass Spectrom. 2008, 19, 1771-1775. 

Collision-induced dissociation mass spectrum of tire proton-bound dimer of isopropanol [(CH2)2CHOH]2H. The mJz 121 ions were first isolated in the trap, followed by resonant excitation of their trajectories to produce CID. Fragment ions include water loss mJz 103), loss of isopropanol mJz 61) and loss of 42 anui mJz 79). (b) Ion-molecule reactions in an ion trap. In this example the mJz 103 ion was first isolated and then resonantly excited in the trap. Endothennic reaction with water inside the trap produces the proton-bound cluster at mJz 121, while CID produces the fragment with mJz 61. 

As with the quadmpole ion trap, ions with a particular m/z ratio can be selected and stored in tlie FT-ICR cell by the resonant ejection of all other ions. Once isolated, the ions can be stored for variable periods of time (even hours) and allowed to react with neutral reagents that are introduced into the trapping cell. In this maimer, the products of bi-molecular reactions can be monitored and, if done as a fiinction of trapping time, it is possible to derive rate constants for the reactions [47]. Collision-induced dissociation can also be perfomied in the FT-ICR cell by tlie isolation and subsequent excitation of the cyclotron frequency of the ions. The extra translational kinetic energy of the ion packet results in energetic collisions between the ions and background... 

In obtaining experimental information about the isomeric forms of ions, a variety of techniques have been used. These include ion cyclotron resonance (ICR),31 flow tube techniques, notably the selected ion flow tube (SIFT),32 and the selected ion flow drift tube (SIFDT)32 (and its simpler variant33), collision induced dissociation (CID),10,11 and the decomposition of metastable ions in mass spectrometers.13 All of these techniques are mentioned in the text of Section in whore they have provided data relevant to the present review. 

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... 

Finally, we would like to point out that in the off-resonance region, the response time of the nonlinearity is limited only by the optical pulse width r, as long as (Ea -Tiaj)/h >>2ir(x ). (8) This is no longer true when collisions (or phonons in solids) are present. For optical frequencies close enough to the absorption edge, the collision induced transitions to the excited state will cause the x s response time to be limited by the relaxation time of the excited states. (8)... 

DGE a AC AMS APCI API AP-MALDI APPI ASAP BIRD c CAD CE CF CF-FAB Cl CID cw CZE Da DAPCI DART DC DE DESI DIOS DTIMS EC ECD El ELDI EM ESI ETD eV f FAB FAIMS FD FI FT FTICR two-dimensional gel electrophoresis atto, 10 18 alternating current accelerator mass spectrometry atmospheric pressure chemical ionization atmospheric pressure ionization atmospheric pressure matrix-assisted laser desorption/ionization atmospheric pressure photoionization atmospheric-pressure solids analysis probe blackbody infrared radiative dissociation centi, 10-2 collision-activated dissociation capillary electrophoresis continuous flow continuous flow fast atom bombardment chemical ionization collision-induced dissociation continuous wave capillary zone electrophoresis dalton desorption atmospheric pressure chemical ionization direct analysis in real time direct current delayed extraction desorption electrospray ionization desorption/ionization on silicon drift tube ion mobility spectrometry electrochromatography electron capture dissociation electron ionization electrospray-assisted laser desorption/ionization electron multiplier electrospray ionization electron transfer dissociation electron volt femto, 1CT15 fast atom bombardment field asymmetric waveform ion mobility spectrometry field desorption field ionization Fourier transform Fourier transform ion cyclotron resonance... 

Scans based on resonant ejection may either be carried out in a forward, i.e., from low to high mass, or a reverse manner. This allows for the selective storage of ions of a certain m/z value by elimination of ions below and above that m/z value from the trap. Thus, it can serve for precursor ion selection in tandem MS experminents. [156,158] Axial excitation can also be used to cause collision-induced dissociation (CID) of the ions as a result of numerous low-energy collisions with the helium buffer gas that is present in the trap in order to dampen the ion motion. [150,156] A substantial increase of the mass range is realized by reduction of both the RF frequency of the modulation voltage and the physical size of theQIT. [154,159,160]... 

In spite of the fact that in alkali vapors, which contain about 1 % diatomic alkali-molecules at a total vapor-pressure of 10 torr, the atoms cannot absorb laser lines (because there is no proper resonance transition), atomic fluorescence lines have been observed 04) upon irradiating the vapor cell with laser light. The atomic excited states can be produced either by collision-induced dissociation of excited molecules or by photodissociation from excited molecular states by a second photon. The latter process is not improbable, because of the large light intensities in the exciting laser beam. These questions will hopefully be solved by the investigations currently being performed in our laboratory. 

The Mg+—CeHe dissociation energy at 0 K was determined to be 134 4 kJmol (1.39 0.10 eV) using collision induced dissociation and 112 kJmoH by laser photodissociation . Using the radiative association kinetics approach to ion cyclotron resonance spectrometry, the value was shown to be the comparable 1.61 eV (155 kJmoU ). It was also shown that the binding of the second benzene to Mg , i.e. the Mg+ (CeHe)—CgHe bond energy, is less than 1.4 eV (135 kJmoU ). 

Collision-induced microwave spectra. Measurements of the dielectric loss by resonant cavity techniques at 9 and 24 GHz were first reported by Birnbaum and Maryott [33], The cavity was at room temperature and filled with carbon dioxide gas at densities up to 100 amagat. The loss, which at not too low frequencies increases as the square of density,... 

SWIFT excitation affords another method of resonance selection or ejection and has been applied in ICP-IT-MS by C. I. Frum to effect both ion isolation and collision-induced dissociation of ions sampled from an ICP [58]. An example of the isolation of 142Ce from a mixture containing all the lanthanide isotopes is shown in Fig. 9.14. In the absence of SWIFT excitation (Fig. 9.14a) space charge effects on both the lanthanides and Y+ are evident (space charge for Th+ is reduced by the prior ejection of lighter ions during the mass scan). Space charge effects are eliminated on application of SWIFT ion isolation. 

Gas-phase acid-base studies are usually performed by using one of the following techniques high-pressure mass spectrometry (HPMS), chemical ionization mass spectroscopy (CIMS) with mass-analysed ion kinetic energy spectroscopy/collision induced dissociation (MIKES/CID), flowing afterglow (FA) or ion cyclotron resonance (ICR) spectrometry. For a brief description of all methods, Reference 8 should be consulted. 

A useful tool to be gained from this theory is the predictive power based on the large-molecule limiting case requirement that, for an intramolecular decay pathway to be available to an "isolated" molecule, the condition pfV >> 1 must be met. When pf is small (usually for small molecules or small energy gaps between initial and final states), it is most likely that no final states are in resonance with the initial state and no mixing occurs an external perturbation is required to produce the transition and the process is observed to be collision-induced. Very small values of Pf, therefore, would indicate the possibility of small-molecule behavior. 

J. L. Carlsten and A. Szoke. Spectral resolution of near-resonant Rayleigh scattering and collision induced resonance fluorescence. Phys. Rev. Lett., 56 667-671 (1976). 

Ionized aniline may exist in a conventional-ion form as well as in isomeric distonic forms, and gas-phase MS experiments performed by Chyall and Kenttamaa134,135 have also been used to form and to study the intrinsic reactivity of these high-energy isomers. Via collision-induced dissociation (CID) of protonated 2-, 3- and 4-iodoanilines in a dual-cell Fourier transform ion cyclotron resonance spectrometer, the 2-, 3- and 4-dehydroanilinium ions were formed as the result of loss of an iodine atom (Scheme 41). Ion/molecule reactions and energy-resolved CID experiments demonstrated that these three ions as well as ionized aniline behave distinctively. The reactivity of three distonic ions... 

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