Hollow cathode discharge ion

In a later study investigating biomass emissions from controlled laboratory fires it was again concluded that PTR-MS measurements underestimated the concentration of HCN, and in this study by roughly a factor of 5 in comparison to values determined by FTIR spectroscopy [17]. From the collected field data, it was found that the HCHO ratios between PTR-MS and FTIR measurements varied significantly with ambient atmospheric humidity, ranging from 0.2 at the lowest humidity to 0.05 at the highest humidity. It was concluded that the addition of water from the hollow cathode discharge ion source into the drift tube needs to be taken into account in addition to the humidity of the inlet air if HCN and HCHO concentrations are to be accurately determined. 

The reaction of metals with energetic hydrogen or deuterium ions is important in nuclear reactors. Ion beams may be generated thermally and allowed to interact with the metal, and the reaction products then may be examined by matrix-isolation techniques. Alternatively, metal atoms are sputtered from a cathodic surface by a low-energy plasma. If or at low P is added to the discharge, then molecular species are formed by the interaction with the sputtered metal atoms. Applied to Cu this technique leads to the identification of CuH and CuD in Ar matrices by their IR spectra. The reacting species are believed to be atomic Cu and H or D formed in the hollow-cathode discharge . 

By plotting ln[Irem/(/ I J + 1)] versus ] (J + 1) for a series of rotational lines a so-called rotational temperature can be determined. It characterizes the kinetic energy of the molecules and radicals, by which the band spectra are emitted. It is also a good approximation of the temperature reflecting the kinetic energy of the neutrals and ions in a plasma. For the case of a hollow cathode discharge the Boltzmann plot and the temperatures as measured from CN and N) band hyper-fine structures are given in Fig. 3. 

Figure 4, Radial profiles of ion densities in a hollow cathode discharge (HCD). The main ions, Ar, ArH, H20, and HsO, in a hollow cathode discharge were measured by mass spectrometric analysis. Conditions 2 cm diameter, 3 cm length, 0.34 torr pressure (Ar with 0.15% H2O), and discharge current of 3 mA. Redrawn from data presented in Ref. [36].

Figure 1 represents radial density profiles of the main ions Ar", ArH, H20, and H30 observed by mass spectrometric analysis in a hollow-cathode discharge of 2 cm diameter and 3 cm length at a pressure of 0.34 torr (Ar with 0.15% H2O) and a discharge current of 3 mA. These main ions are created in the following processes ... 

The long absorption cells naturally lend themselves to a hollow-cathode discharge configuration for the study of molecular ions. A preliminary experiment revealed the HCO line at 1 THz with a signal-to-noise ratio (100 1 with a 1 s time constant) equivalent to that obtained using the laser sideband technique (16). Possible transitions in H2D and OH have also been observed however they are weak and only tentatively identified, and further work is underway. 

More than 50% dissociation was observed in d.c. hollow cathode discharges in NF3 for an initial pressure of 80 mTorr. F and Fj are formed directly by the discharge, with F" being dominant [5]. The negative ion density (2.4x 10 cm ) is one to two orders of magnitude larger than the electron density (5.8 x 10 cm ) [6]. 

Hollow Cathode Discharges. Discharges through flowing NH3 or NH3-He mixtures produce NH ions in the electronic ground and various excited states. This technique has been applied for spectroscopic studies of NH, as there are observations of the A B A, and C 2 - X emission band systems in the visible and UV [19 to 23] (cf. pp. 146/7), the v = 1 (-0 vibration-rotation transitions in the X and a 2 states, and transitions between the X and a states [24, 25] (cf. p. 146). 

Figure 3.10 Schematic cross section of an ion source and drift tube from the laboratory of one of the authors. Here the drift tube is constructed from a single block of Teflon and the metal electrodes are located in slots on the outside of the drift tube. A Venturi inlet was employed to introduce the analyte gas into the drift tube. HC refers to the hollow cathode discharge region...

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