Collision energy normalized

How many collisions occur, roughly, in a liter of gas at atmospheric pressure, and what fraction of these collisions will normally give rise to a reaction (assuming commonly applied reaction temperatures and barrier energies) ... 

Fig. 3. The normalized excitation functions in A2 versus collision energy for the two isotopic channels for the F+HD reaction. The solid line is the result of quantum scattering theory using the SW-PES. The QCT simulations from Ref. 71 are plotted for comparison. The experiment, shown with points, is normalized to theory by a single scaling factor for both channels. Also shown in (a) is the theoretical decomposition of the excitation function into direct and resonant contributions using the J-shifting procedure.

Figure 19. Deviation of sum of partial cross sections from total ionization cross section, normalized to total ionization cross section, is plotted against the collision energy. All cross sections are calculated on basis of description of Penning process by local complex potential. Deviation is measure of inconsistency of their desorption for case of system He(2 S )-H.

Determination of MS/MS conditions using the MALDI ion source coupled to the triple-quadrupole mass spectrometer takes a different approach (Kovarik et al., 2003) which at present is not as easily automated. As mentioned earlier, some product ion spectra will contain additional fragment ions not related to the analyte due to isobaric matrix peaks. However, MS/MS conditions previously obtained by using an ESI-MS/MS system can be directly ported over to the MALDI triple-quadrupole mass spectrometer. These conditions provide the advantage of product ion selection for SRM of the analyte. In the typical high-throughput environment, individual methods for each chemical entity are not normally utilized. Rather, the semioptimized template-style methods referred to above are often used wherein a few values of collision energy are combined with the appropriate SRM and polarity. These methods are ported to the MALDI triple quadmpole mass spectrometer, and no further... 

Ionization, charge stripping or charge inversion (normally observed at collision energies of about 1 keV) ... 

We denote by G the set of all the experimentally observable quantities (called physical observables) which must be reproduced. Such quantities are, for instance, the collision energy, the quantum numbers defining the intramolecular state (vibrations and the principal quantum number of rotation), the total angular momentum etc... However, there are other dynamical variables which have a clear meaning in Classical Mechanics but correspond to no physical observable because of the Uncertainty Principle. We call them phase variables and denote them globally by g. The phase variables must be given particular values to obtain, at given G, a particular trajectory. Such variables are, for instance, the various intramolecular normal vibrational phases, the intermolecular orientation, the secondary rotation quantum numbers, the impact parameter, etc... Thus we look for relationships of the type qo = qq (G, g) and either qo = qo (G, g) or po = Po (G, g)... 

Figure 17. OH production versus photolysis wavelength for room temperature COj/HI samples (a) HI 300K absorption coefficient (arbitrary units) versus wavelength, with the I contribution removed, (b) Normalized OH LIF signals divided by curve (a), yielding relative OH(t) = 0, low-N) production rates, (c) Curve (b) divided by CM. yielding relative OH(b = 0, low-N) reaction probabilities. The arrows indicate where OH(v = 0) rotational distributions were obtained (see Figure 14). Also shown are the CM collision energies and E values appropriate to the different photolysis wavelengths.

Although libraries based on MS-MS in a triple-quadrapole [98] and an ion-trap instrument [99] have been described, in-source CID is applied in most cases, e.g., [100-104]. In this respect, it must be mentioned that an ion-trap can have some distinct advantages in building libraries, because good mass spectral reproducibility between ion-trap instruments can be achieved by the use of normalized collision energy [99]. Recently, Marquet et al. [105] evaluated MS-MS on a quadrapole-linear-ion-trap hybrid (Q-LIT) instmment as an alternative to the in-source CID. Promising preliminary results were obtained. Comparison of MS-MS spectra from different instraments was reported by the same group [96]. 

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