Triple collisions

Each time a molecule of H collides with an iodine molecule, reaction may occur. The frequency of these encounters, for a particular Ha molecule, is determined by how many I molecules are present. Doubling the number of 1 molecules per unit volume would just double the collisions. Tripling the number of I molecules per unit volume would triple the collisions. Since the iodine partial pressure fixes the iodine concentration, the rate of the reaction is proportional to the iodine partial pressure ... 

K has been identified as CFl200I-I from its chemistry the reaction mechanism is insertion [115], Collision-induced dissociation (in a SIFT apparatus, a triple-quadnipole apparatus, a guided-ion beam apparatus, an ICR or a beam-gas collision apparatus) may be used to detemiine ligand-bond energies, isomeric fomis of ions and gas-phase acidities. 

An example of linked scanning on a triple quadrupole instrument. A normal ion spectrum of all the ions in the ion source is obtained with no collision gas in Q2 all ions scanned by Q1 are simultaneously scanned by Q3 to give a total mass spectrum (a). With a collision gas in Q2 and with Q1 set to pass only m+ ions in this example, fragment ions (f, fj ) are produced and detected by Q3 to give the spectrum (b). This CID spectrum indicates that both f, and fj are formed directly from m+. 

Q/TOF, used for two mass analyzers (quadrupole and time-of-flight) used in combination QQQ (or QqQ)- a triple quadrupole analyzer (if q is used, it means the central quadrupole is also a collision cell)... 

A minima] set of symmetric binary and triple collision rules conserving both momentum and particle number-... 

Whatever scheme we choose for treating head-on collisions, however, unless we also have triple collisions, spurious conservations laws are inevitable. In addition to the total particle numbei and momentum, it is easy to see that head-on collisions also conserve the difference in particle number in opposite directions-, that is, the difference in particle numbers in directions c and c +s- A simple way to fix this problem is to introduce a triple-collision of the form (cp, Ck+2, k+4) ( k+i, Ck+s, Ck+5)... 

Handling the triple-collision gain-lo.ss term in the same way, the complete two- and three- particle collision term for the Cp direction can be written in the following form [hciss88b] ... 

Tandem mass spectrometry (MS/MS) is a method for obtaining sequence and structural information by measurement of the mass-to-charge ratios of ionized molecules before and after dissociation reactions within a mass spectrometer which consists essentially of two mass spectrometers in tandem. In the first step, precursor ions are selected for further fragmentation by energy impact and interaction with a collision gas. The generated product ions can be analyzed by a second scan step. MS/MS measurements of peptides can be performed using electrospray or matrix-assisted laser desorption/ionization in combination with triple quadruple, ion trap, quadrupole-TOF (time-of-flight), TOF-TOF or ion cyclotron resonance MS. Tandem... 

Marsault-Herail F., Marsault J. P., Michond G., Levi G. Raman scattering Orientational motion and collision frequency in liquid CF4 from the triple to critical point, Chem. Phys. Lett. 31, 335-9 (1975). 

The results thus show that ammonia DCI-MS/MS using a triple quadrupole mass spectrometer is a convenient method for the detection of additives in PE samples. The softness and selectivity provided by ammonia DCI in combination with the specificity provided by CID, demonstrate great potential for identification of additives directly from PE extracts. The utility of DCI in the quantitative analysis of additives has still to be explored. DCI-MS/MS (B/E) with high collision... 

Selection of a suitable ionisation method is important in the success of mixture analysis by MS/MS, as clearly shown by Chen and Her [23]. Ideally, only molecular ions should be produced for each of the compounds in the mixture. For this reason, the softest ionisation technique is often the best choice in the analysis of mixtures with MS/MS. In addition to softness , selectivity is an important factor in the selection of the ionisation technique. In polymer/additive analysis it is better to choose an ionisation technique which responds preferentially to the analytes over the matrix, because the polymer extract often consists of additives as well as a low-MW polymer matrix (oligomers). Few other reports deal with direct tandem MS analysis of extracts of polymer samples [229,231,232], DCI-MS/MS (B/E linked scan with CID) was used for direct analysis of polymer extracts and solids [69]. In comparison with FAB-MS, much less fragmentation was observed with DCI using NH3 as a reagent gas. The softness and lack of matrix effect make ammonia DCI a better ionisation technique than FAB for the analysis of additives directly from the extracts. Most likely due to higher collision energy, product ion mass spectra acquired with a double-focusing mass spectrometer provided more structural information than the spectra obtained with a triple quadrupole mass spectrometer. 

Apparatus, developed in this laboratory for two types of thermochemical measurements—(a) gas-phase ion molecule equilibria and (b) collision-induced dissociation (CID) threshold measurements—will be described. For both purposes, a triple quadrupole mass spectrometer is used. It is only the front end modifications that provide the conditions for (a) or (b). 

Figure 9. Apparatus for the determination of CID thresholds. Electrospray ions are produced as in Figures 4 and 7, however pressure reduction capillary CAP leading to 10 torr low pressure chamber LPS is coaxial with orifices leading to triple quadrupole. The IT chamber at 10 torr is used for ion thermalization. Collision chamber at Q2 is usually used with collision gas Ar or Xe. The last quadrupole Q3 is not shown on Figure.

One of the most common couplings of analyzers for tandem MS is the triple quadrupole. Its notation is QqQ, where the capital Q indicates a quadrupole analyzer and the lowercase q is for a RF-only quadrupole that constitutes the collision cell. 

Big Bang nucleosynthesis (cosmic nucleosynthesis) Proton-proton cycle Triple He collisions Alpha capture CNO cycle Neutron capture High-energy photon collisions produce antimatter-matter pairs. This leads to H,D, He and some Li nuclei Hydrogen burning to produce He 12C production Addition of 4He to the nucleus Production of 13C, 13N, 14N and 150 Post-Fe nuclei... 

Figure 3.9 Conceptual view of tandem mass spectrometry with a tandem-inspace triple quadrupole mass analyzer." The first mass analyzer (Ql) selects the precursor ion of interest by allowing only it to pass, while discriminating against all others. The precursor ion is then fragmented, usually by energetic collisions, in the second quadrupole (q2) that is operated in transmissive mode allowing all fragment ions to be collimated and passed into the third quadrupole (Q3). Q3 performs mass analysis on the product ions that compose the tandem mass spectra and are rationalized to a structure.

A Waters Micromass triple quadrupole mass spectrometer was used with an electrospray ionization interface in positive ionization mode desolvation gas (400), cone gas (70), collision gas (2.74 x 10 3 mbar), capillary (3.0 kV), cone (14 (kV), source temperature (105°C), and desolvation temperature (300°C). The detection and quantitation of amlodipine and nimodipine were performed... 

The ion trap mass analyzer is similar to the quadrupole but with the important distinction that it can isolate and trap ions in an electrical field. Notably, the ion trap differs significantly from quadrupoles in design and operation in that triple quadrupoles perform tandem mass analysis on ions as they pass through an analyzer ion traps are capable of isolating and retaining specific ions for fragmentation upon collision with an inert gas in the same cell. An ion trap is about the size of a tennis ball and consists of a donut-shaped electrode and two perforated disk-like end-cap electrodes. 

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