Collisional activation process

The general nature of the elementary physical processes which contribute to the overall chemical elementary reaction step (1.1) is well known. Collisional activation processes are described symbolically by the equation... 

A product ion scan. Source ions (mT, f,, . .., fs ) are selected by setting Ql, in this case, to pass only m,. Collisional activation of these ions in Q2 induces dissociation to give fragment ions (f,, fj, f, ), which are detected by scanning Q3. The symbolism for this process is shown. 

Collision of normal ions from the first quadrupole with gas molecules in the second quadrupole increases fragmentation, a process known as either collisionally induced dissociation (CID) or collisionally activated decomposition (CAD). 

Collision-induced dissociation (or decomposition), abbreviated CID. An ion/neutral process wherein the (fast) projectile ion is dissociated as a result of interaction with a target neutral species. This is brought about by conversion during the collision of part of the translational energy of the ion to internal energy in the ion. The term collisional-activated dissociation (or decomposition), abbreviated CAD, is also used. 

Voyskner, R. D. Pack, T. Investigation of collisional-activation decomposition process and spectra in the transport oregion of an electrospray single-quadrupole mass-spectrometer. Rapid Comm. Mass Spectrom. 1991, 5, 263-268. 

In an attempt to explain the discrepancy in terms of a participation of internal degrees of freedom of the C02-M complex in the process of collisional activation, some authors have invoked the classical rrk expression for the rate of energization... 

The experimental data indicate a high activation energy for the reaction forming SO3, about 75 kcal/mol. It has been suggested that the SO3 formation process may involve collisional activation of SO2 to an excited (triplet) state,... 

Selected reaction monitoring is one of several techniques carried out by consecutive mass filters. These techniques are collectively called tandem mass spectrometry or mass spectrometry/mass spectrometry or simply MS/MS. The process In Q2 is collisionally activated dissociation. 

Rates of Gas-Phase Reactions. Reaction rates have been reported for only a few CVD gas-phase reactions, and most reports are primarily for the silane system. Because of the high temperatures and low pressures used in CVD, the direct use of reported gas-phase rate constants must be done with care. In addition to mass-transfer and wall effects, process pressure may be another factor affecting reaction rates. Process pressure affects major CVD processes, such as the deposition of Si from SiH4 and GaAs from Ga(CH3)3, reactions that involve unimolecular decomposition. The collisional activation, deactivation, and decomposition underlying these reactions can be summarized qualitatively by the following reactions (139, 140) ... 

As all of these processes, by necessity, can only result from electronic excitation, this suggests that collision activation under these conditions leads at least in part to electronic excitation. However, especially for larger molecules, the mechanisms of collisional activation are more likely to involve vibrational excitation. In this case, it may occur through impulsive collision of the target atom or molecule with a selected atom or group of atoms in the region of the collision site. 

An intriguing application of this hypothesis may have been observed in the mass spectrometric behavior of MTO.86 Loss of H2 and CO from the parent ion were the major processes observed in both metastable ion and collisional activation mass spectrometry. Both were viewed as unusual the latter, in particular, required a rationale for forming a C—O bond. The authors proposed migration of carbon to oxygen in the parent ion to form a methoxyrhenium complex of the same mass, followed by sequential back migration of the hydrogens ... 

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