Ion translational energy

However, most collisions are not head-on , but occur at some angle 0. Increasing mAB makes ifintmax decrease, whereas larger wn is beneficial for energy transfer. In CID-MIKES the center of the peak is shifted to the low mass side, i.e., to the low ion translational energy side, because the uptake Q originates from a loss in Slab- [120-125] The relationship between AElab and Q can be expressed as [122]... 

REACTION INCIDENT-ION TRANSLATIONAL ENERGY EMITTING SPECIES wavelengths and/or TRANSITIONS OBSERVED VIBRATIONAL AND ROTATIONAL POPULATIONS OF EMITTING STATE REFERENCE... 

Excitation functions measured for different ionizing electron energies importance of vibrational energy decreases with increasing ion translational energy 93... 

The El fragmentation pattern of exo- (108) and endo- (109) 5-chloronorbornan-2-ones and of exo- (110) and endo- (111) 6-chloronorbornan-2-ones is stereo-dependent220. Information on the ion structures have been obtained by energy-resolved mass spectrometry (ERMS), (ERMS is obtained in a triple quadrupole instrument by plotting the relative abundance of the ions after collisional activation as a function of the parent ion translational energy). 

An overall view shows the CID process as a sequence of two steps. The first step is very fast (10 14 to 10 16 s) and corresponds to the collision between the ion and the target when a fraction of the ion translational energy is converted into internal energy, bringing the ion into an excited state. The second step is the unimolecular decomposition of the activated ion. The collision yield then depends on the activated precursor ion decomposition probability according to the theory of quasi-equilibrium or RRKM. This theory is explained elsewhere. Let us recall that it is based on four suppositions ... 

The vast majority of the work on ion-molecule kinetics has been performed at room temperature. A fraction of these room temperature kinetic studies have been made as a function of ion translational energy. However, temperature dependent studies have been limited mostly to... 

The absence of ion translational energy effects on the C8 distribution is also indicated by the lack of an applied field effect. We conclude that vibrational de-excitation is occurring and that argon is much more effective for vibrational de-excitaton than is neon. Such a large difference in vibrational deactivation efficiency between neon and argon is somewhat surprising. However, deactivation of ions may be more sensitive to polarizability effects than is deactivation of neutral molecules. 

Fig. 5. Comparison of numerically calculated cross sections for methyl cyanide-parent ion collision with various theoretical cross sections. All cross sections are plotted as functions of ion translational energy for one rotational temperature = 500°K electronic polarizability a, 3.8 A dipole moment fi., 3.92 Debye units.

Another effect of ion translational energy is illustrated by Table II, which reports the reactions of ethylene ions with ordinary propane as a... 

This indication of the sensitivity of product distribution to internal energy of the reaction complex prompted some additional experiments. These included the variation of collision chamber temperature and of ion translational energy. 

KEfjjj l= final kinetic energy P(e) = internal energy distribution Q = inelasticity of collision T = initial kinetic energy (ion translational energy) V = total... 

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