Internal ionization

A.J. BeU and S.K. Ross, Reverse flow continuous corona discharge ionization. International Journal of Mass Spectrometry 218(2) (2002) LI—L6, also found in part at International Journal for Ion Mobility Spectrometry 5(3) (2002) 95—99. 

Kaesdorf S, Hartmann M, Schroder H, and Kompa KL (1992) Influence of laser parameters on the detection efficiency of sputtered neutrals mass spectrometry based on non-resonant multiphoton ionization. International Journal of Mass Spectrometry and Ion Processes 116 219-247. 

Reference values for the acylcarnitines are derived from >500 patients, mostly pediatric (0.2-16 yrs), evaluated for metabolic disorders in the author s laboratory but with no manifest biochemical evidence of disease. Individuals with any markedly abnormal values were discounted. The analytical method used was tandem mass spectrometry with electrospray ionization. Internal standards used were stable isotope-labeled analogs of acetyl, propionyl, butyryl, octanoyl and palmitoyl carnitine. The values for straight-chain C2, C3, C4, C5, C6, C8, CIO, C14, C16 and Cl8 1 species are in pmol/1 and are derived from calibration curves using analytical standards all other values are ratios of the signal for the compound to an appropriate internal standard. All values are mean + 2 std. dev. except where a range is given... 

In electron ionization, internal energy distribution is very important This means that ions possess very different internal energies among the formed M+- ion population. This phenomenon occurs because (1) all the molecules M do not arrive in the source with the same energy because they clash and collide with the omnipresent helium atoms and residual atmospheric molecules, and (2) all the electrons emitted by the filament do not collide with the molecules with the same kinetic energy (70 eV is the average value). These electrons have different speed characteristics according to the part of the filament that emits them they are also subject to collisions with helium atoms and HjO, Nj, and O2 molecules present in the source. 

A-B relative or external motion undergo free-free transitions (E., E. + dE.) (Ej Ej+ dE within the translational continuum, while the structured particles undergo bound-bound (excitation, de-excitation, excitation transfer) or bound-free (ionization, dissociation) transitions = (a, 3) ->/= (a, (3 ) in their internal electronic, vibrational or rotational structure. The transition frequency (s ) for this collision is... 

It is well known that the electron-impact ionization mass spectrum contains both the parent and fragment ions. The observed fragmentation pattern can be usefiil in identifying the parent molecule. This ion fragmentation also occurs with mass spectrometric detection of reaction products and can cause problems with identification of the products. This problem can be exacerbated in the mass spectrometric detection of reaction products because diese internally excited molecules can have very different fragmentation patterns than themial molecules. The parent molecules associated with the various fragment ions can usually be sorted out by comparison of the angular distributions of the detected ions [8]. 

Dagdigian P J, Varley D F, Liyanage R, Gordon R J and Field R W 1996 Detection of DCI by multiphoton ionization and determination of DCI and HCI internal state distributions J. Chem. Phys. 106 10 251-62... 

Again consider the v=0 N2 ionization treated in Problem 11 of this chapter. If, subsequent to ionization, the produced were probed to determine their internal... 

Most of the ions produced by either thermospray or plasmaspray (with or without the repeller electrode) tend to be very similar to those formed by straightforward chemical ionization with lots of protonated or cationated positive ions or negative ions lacking a hydrogen (see Chapter l).This is because, in the first part of the inlet, the ions continually collide with neutral molecules in the early part of their transit. During these collisions, the ions lose excess internal energy. 

Some of the target molecules gain so much excess internal energy in a short space of time that they lose an electron and become ions. These are the molecular cation-radicals found in mass spectrometry by the direct absorption of radiation. However, these initial ions may react with accompanying neutral molecules, as in chemical ionization, to produce protonated molecules. 

Usually, FAB yields molecular or quasi-molecular ions, which have little excess of internal energy and therefore do not fragment. This ionization method is mild and good for obtaining molecular mass (molecular weight) information. 

Associative ionization. Occurs when two excited gaseous atoms or molecular moieties interact and the sum of their internal energies is sufficient to produce a single, additive ionic product. 

Auto ionization. Occurs when an internally supraexcited atom or molecular moiety loses an electron spontaneously without further interaction with an energy source. (The state of the atom or molecular moiety is known as a pre-ionization state.)... 

Penning ionization. Occurs through the interaction of two or more neutral gaseous species, at least one of which is internally excited ... 

U.S. radiation protection guidelines are estabHshed by the National CouncH on Radiation Protection and Measurement (NCRP) and are based on the recommendations of the International Commission on Radiological Protection (ICRP). The National Research CouncH also sponsors a report from its advisory committee on the biological effects of ionizing radiations (20). 

Radiation Dosimetry. Radioactive materials cause damage to tissue by the deposition of energy via their radioactive emissions. Thus, when they are internally deposited, all emissions are important. When external, only those emissions that are capable of penetrating the outer layer of skin pose an exposure threat. The biological effects of radiation exposure and dose are generally credited to the formation of free radicals in tissue as a result of the ionization produced (17). 

Fig. 15. Ion movements in the electro dialysis process. Courtesy U.S. Agency for International Development, (a) Many of the substances which make up the total dissolved soHds in brackish water are strong electrolytes. When dissolved in water, they ionize ie, the compounds dissociate into ions which carry an electric charge. Typical of the ions in brackish water are Cl ,, HCO3, , and. These ions tend to attract the dipolar water molecules...

Internal and External Phases. When dyeing hydrated fibers, for example, hydrophUic fibers in aqueous dyebaths, two distinct solvent phases exist, the external and the internal. The external solvent phase consists of the mobile molecules that are in the external dyebath so far away from the fiber that they are not influenced by it. The internal phase comprises the water that is within the fiber infrastmcture in a bound or static state and is an integral part of the internal stmcture in terms of defining the physical chemistry and thermodynamics of the system. Thus dye molecules have different chemical potentials when in the internal solvent phase than when in the external phase. Further, the effects of hydrogen ions (H" ) or hydroxyl ions (OH ) have a different impact. In the external phase acids or bases are completely dissociated and give an external or dyebath pH. In the internal phase these ions can interact with the fiber polymer chain and cause ionization of functional groups. This results in the pH of the internal phase being different from the external phase and the theoretical concept of internal pH (6). 

FIG. 19-60 Internal configuration of roll-tvpe electro.static. separator, ionizing Diode. (Cowiosij Carpco, Inc.)... 

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