Corona ionization products

L8. Loeb, L. B., The Threshold for the positive pre-onset burst pulse corona and the production of ionizing photons in air at atmospheric pressure, Phys. Rev. 73, 798 (1948). 

The desorption of explosives from the passes was achieved by short wave infrared radiation. The vapors produced were drawn into a triple quadrupole mass spectrometer (MS/MS) and were monitored in the selected reaction monitoring (SRM). Ionization is carried out by corona discharge, followed by APCI. Ions formed from most explosives are M, [M-H]-, and adduct ions. One of these ions is selected to pass into the collision cell, to react with molecules of nitrogen, as a result of which a series of product ions are formed. In the SRM mode, one precursor ion and one product ion are chosen for each compound. The first and third quadruples are adjusted in order to enable SRM transition between these two ions. 

The corona cell impedance, which is mainly capacitive before corona breakdown, acquires a resistive component after breakdown which depends on the rate of production of ionized and electrically conducting chemical entities. The a.c. voltage at the plates of the power tetrodes will lag the plate current by a large angle before power is consumed, and the plate current will be collected at a high rather than a low value of plate voltage. Thus, the power dissipated by the tetrodes will be high under no-load conditions. 

Other ionization techniques are sometimes used, such as atmospheric pressure ionization (API), photoionization, and chemical ionization. Of these, API has been the most widely applied, and involves the production of ions at high pressure in a corona discharge. The ions are then swept by the bulk gas flow into a region where they are extracted by lens voltages into the vacuum part of the mass spectrometer for mass separation and detection. 

Ion-molecule reactions occurring at atmospheric pressure are employed for analyte ion production in atmospheric pressure chemical ionization (APCI). Basically, APCI represents an atmospheric pressure variant of vacuum chemical ionization (Cl, Chap. 7). In APCI the reagent ion plasma is maintained by a corona discharge between the sharp tip of a needle and the spray chamber serving as the counter electrode. 

All stars with surface temperatures cooler than about 7500 K appear to have convective envelopes, the primary optical signature of which is the emission observed in the resonance lines of ionized calcium, Ca II, at A.A.3927 and 3933 A. The strength of this emission appears to decline with age, as does the rotational velocity of the star, thus supporting the contention that magnetic activity is the primary agent for the production of chromospheres and coronae in low-mass stars. We shall return to this point later. 

Aqueous solutions of cationic polyacrylamide (0.25 wt. % in deionized water) were prepared by rolling for 48 hours. Suspensions of 0.2 wt. % clay in deionized water were similarly prepared. Each 10 x 10 cm piece of PET film, rinsed with methanol and deionized water, was corona treated with a BD-20C Corona Treater (Electro-Technic Products Inc., Chicago, IL), prior to LbL deposition. The substrate was initially dipped in the C-491 solution for 5 minutes, followed by rinsing with de-ionized water and blow drying with air. This same procedure was followed with the clay solution, followed by one minute of deposition for all subsequent dips. The entire dipping procedure was accomplished with a home-built robotic system (12). 

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