Plasma helium

Poljraer surfaces can be easily modified with microwave or radio-frequency-energized glow discharge techniques. The polymer surface cross-links or oxidizes, depending on the nature of the plasma atmosphere. Oxidizing (oxygen) and nonoxidizing (helium) plasmas can have a wide variety of effects on polymer surface wettability characteristics (92). 

MIP-MS Microwave-induced (helium) plasma Microwave-induced electrical discharge... 

A. Montaser, S. K. Chan, and D. W. Koppenaal. Inductively Coupled Helium Plasma as an Ion Source for Mass Spectrometry. Anal. Chem., 59(1987) 1240-1242. 

The resist has been used as a mask in wet etching and in lift-off processes, and more recently in etching chromium films in a chlorine-oxygen-helium plasma. In the latter, the etch rates have ranged from 4 to 5.5nm/min at lOOW power in a barrel type reactor. Chromium etches at about 6.5nm/min under these conditions. The etch rate of the resist appears to be independent of the degree to which it has been cured before exposure, so the sensitive form described here is just as effective a mask as the highly cross-linked resists described earlier, at least in the chromium etching process. 

Furnace atomisation plasma emission spectrometry (FAPES) this consists of an atmospheric pressure source combining a capacitively coupled radiofrequency helium plasma formed inside a graphite tube which contains an axial powered electrode. This miniplasma has rarely been used in analytical atomic spectrometry, probably because of the small number of users and a lack of information about its applications and capabilities [7]. 

Mass spectrum from Y. Su, Y. Duan, and Z. Jin, Helium Plasma Source Time-of-Flight Mass Spectrometry Off-Cone Sampling tor Elemental Analysis, Anal. Chem. 2000, 72, 2455. 

Eluate from a chromatography column can be passed through a plasma to atomize and ionize its components and measure selected elements by atomic emission spectroscopy or mass spectrometry. An atomic emission detector directs eluate through a helium plasma in a microwave cavity. Every element of the periodic table produces characteristic emission that can be detected by a photodiode array polychromator (Figure 20-14). Sensitivity for sulfur can be 10 times better than the sensitivity of a flame photometric detector. 

The TOF distribution for = 540 meV has been obtained in a completely different way. The helium plasma of a high-current arc discharge has been expanded through a small nozzle hole, giving directly a supersonic He(23S) beam of higher kinetic energy (see Section III.A.6). 

Figure 18 shows differential cross sections measured using the helium plasma jet described in Section III.A.6. It is surprising that so much structure is still resolved, even though the velocity resolution of the beam is only 30%. No fit has so far been attempted for these data. 

The atomic emission detector is a tunable, element-specific detector that uses microwave-induced helium plasma to generate temperatures high enough to break molecular bonds. The generated free atomic species undergo electron excitation to higher energy states, followed by relaxation and photon emission at characteristic frequencies... 

Environmental Tin, lead and mercury Organolead, organotin and organomercury compounds Helium plasma (Hewlett Packard) 1-2.5 ng ml"1 Liu et al. (1994)... 

Spiked food samples C, H, N, 0, Br, F, Cl, P and S Twenty different herbicides Helium plasma (Hewlett Packard) 0.1-75 pg s"1 Wylie and Oguchi (1990)... 

Natural waters Mercury Methyl, ethyl and inorganic Helium plasma TM10i cavity 0.05 ng T1 methyl and ethyl mercury Emteborg et al. (1993)... 

Liu, Y. and Lopez-Avila (1993) On-line microwave-induced helium plasma atomic emission detector for capillary zone electrophoresis./. High Resol. Chromatogr., 16, 717-720. 

Mohamad, A.H., Creed, J.J., Davison, T.M. and Caruso, J.A. (1989) Detection of halogenated compounds by capillary gas chromatography with helium plasma mass-spectrometry detection. Appl. Spec., 43, 1127-1131. 

Bache, C. A., Lisk, D. J. Gas chromatographic determination of organic mercury compounds by emission spectrometry in a helium plasma. Application to the analysis of methylmercuric salts in fish. Anal. Chem. 43, 950 (1971). 

Phosphorus-sulphur type Helium - plasma microwave 0.05-0.5 mg kg-1 [392]... 

Estes el al. [722] described a method for the measurement of triethyl- and trimethyllead chloride in potable water, using fused silica capillary column gas chromatography with microwave excited helium plasma lead specific detection. Element specific detection verified the elution of lead species, a definite advantage to the packed column method. The method involved the initial extraction of trialkyllead ions from water into benzene, which was then vacuum reduced to further concentrate the compounds. Direct injection of the vacuum concentrated solutions into the gas chromatography-microwave excited helium plasma system gave delectability of triethyllead chloride at the 30mg L 1 level... 

The beryllium acetylacetonate is separated in a gas chromatograph and injected into the helium plasma emission spectrometer. The detection limit is lOpg in a 30mL water sample and the standard deviation was 4.1% at lOng of beryllium. 

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