Microwave excitation

Moisan, M. and Pelletier, J. (eds) (1992) Microwave excited plasmas, Elsevier Science Publishers, Amsterdam, pp. 5-25. 

Flash vacuum thermolysis (FVP) at 600°C or microwave excitation of 1-substituted perhydropyrido[l,2-f][l,3]oxa-zines afforded 1-substituted 1,4,5,6-tetrahydropyridines <2005TL5451>. Perhydropyrido[l,2-f][l,3]oxazin-l-ones were hydrolyzed with 2M ethanolic KOH to 2-(2-hydroxyalkyl)piperidines <1996CJC2434, 2005EJ01378>. (+)-9- />z -6-Epipinidinol 102 was similarly obtained from 3,8-dimethylperhydropyrido[l,2-f][l,3]oxazin-l-one 101 (Equation 16) <1998T13505>. 

Ideally, the emission line used should have a half-width less than that of the corresponding absorption line otherwise equation (8.4) will be invalidated. The most suitable and widely used source which fulfils this requirement is the hollow-cathode lamp, although interest has also been shown in microwave-excited electrodeless discharge tubes. Both sources produce emission lines whose halfwidths are considerably less than absorption lines observed in flames because Doppler broadening in the former is less and there is negligible collisional broadening. 

Microwaves Excitation between rotational quantum states Rotational spectroscopy... 

Where vapour discharge lamp sources exist (for volatile elements such as Hg, Na, Cd, Ga, In, T1 and Zn) they can be used. Hollow-cathode lamps are insufficiently intense, unless operated in a pulsed mode. Microwave-excited electrodeless discharge lamps are very intense (typically 200-2000 times more intense than hollow-cathode lamps) and have been widely used. They are inexpensive and simple to make and operate. Stability has always been a problem with this type of source, although improvements can be made by operating the lamps in microwave cavities thermostated by warm air currents. A typical electrodeless discharge lamp is shown in Fig. 6.3. 

Light Emission from a Microwave-Excited Discharge... 

The steady state OH concentration in the atmosphere has been measured by the fluorescence technique using a dye laser tuned near 2820 A [Wang and Davis (1006), Davis ct al. (267)] or a microwave excited OH resonance lamp [Anderson (42)]. 

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... 

Fig. 10. Example of a Larmor resonance in the precision trap. Here the spin flip probability is plotted versus the ratio g = 2ui L/u)ec of the microwave excitation frequency (jj L and the electron s free space cyclotron frequency ui%. This is convenient because this ratio is independent of the magnetic field...

The first stage was the production of a pulsed free-jet molecular beam of helium containing 20% CO, which was then crossed with an electron beam to produce ionisation. The ions were produced close enough to the beam nozzle for cooling to occur downstream. Some 4 cm from the nozzle the beam entered a confocal Fabry-Perot cavity where it was exposed to millimetre wave radiation close to 120 GHz in frequency. Following microwave excitation, when on resonance, the beam was probed with a Nd YAG pumped dye laser beam with the frequency chosen to drive rovibronic components of the A 2 U-X 2 + band system. Figure 11.54 shows two recordings of a spin component of the lowest rotational transition the line shown in (a) is... 

Another approach to the production of UV photons includes the development of electrode-less discharge lamps driven by microwave excitation (e.g. Fassler et al., 2001, Ametepe et al., 1999, He et al., 1998). This type of lamp is shown in Fig. 4-17. In this case, the excitation of mercury vapor within the discharge gap is achieved by coupling in the energy with a water-cooled high-frequency spool. This concept may be a very convenient tool for microwave photochemistry experiments by simultaneous combination of microwave and VUV/UV irradiation of aqueous systems (c.f Klan et al., 2001, 1999). 

He Z, Prelas MA, Meese JM, Lin L-T (1998) Microwave Excitation and Applications of an Elliptical Excimer Lamp, Laser Part. Beams 16, No. 3 509-524. 

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