Neon atomic emission

Lasers (see Chapter 9) are sources of intense, monochromatic radiation which are ideal for Raman spectroscopy and have entirely replaced atomic emission sources. They are more convenient to use, have higher intensity and are more highly monochromatic for example, the line width at half-intensity of 632.8 nm (red) radiation from a helium-neon laser can be less than 0.05 cm. ... 

A low-pressure atomic emission lamp such as neon or argon emits atomic lines of sufficiently narrow linewidth to be considered infinitely narrow for most Raman spectrometers (an example is shown in Fig. 10.1). The width of atomic emission lines depends on temperature and pressure, but is generally... 

If the light emitted by the neon is passed through a glass prism, neon s atomic emission spectrum is produced. The atomic emission spectrum of an element is the set of frequencies of the electromagnetic waves emitted by atoms of the element. Neon s atomic emission spectrum consists of several individual lines of color corresponding to the frequencies of the radiation emited by the atoms of neon. It is not a continuous range of colors, as in the visible spectrum of white light. 

A FIGURE 6.10 Atomic emission of hydrogen and neon. Different gases emit li t of different characteristic colors when an electric current is passed through them. 

Neon lights" is a generic term for atomic emission involving various noble gases, mercury, and phosphor. The UV light from excited mercury atoms causes phosphor-coated tubes to fluoresce white light and other colors. 

Light Emission Excited neon atoms emit iight when eiectrons in higher energy ieveis faii back to the ground state or to a iower-energy excited state. 

Figure 12 Calibration spectrum used for the CCD echelle spectrograph. The lower curves represent the white-light response for the different echelle orders used. The lines represent atomic emission lines from a neon lamp used for wavelength calibration. (Adapted with permission from Ref. 133.)...

As indicated in Fig. 21.3, for both atomic absorption spectroscopy and atomic fluorescence spectroscopy a resonance line source is required, and the most important of these is the hollow cathode lamp which is shown diagrammatically in Fig. 21.8. For any given determination the hollow cathode lamp used has an emitting cathode of the same element as that being studied in the flame. The cathode is in the form of a cylinder, and the electrodes are enclosed in a borosilicate or quartz envelope which contains an inert gas (neon or argon) at a pressure of approximately 5 torr. The application of a high potential across the electrodes causes a discharge which creates ions of the noble gas. These ions are accelerated to the cathode and, on collision, excite the cathode element to emission. Multi-element lamps are available in which the cathodes are made from alloys, but in these lamps the resonance line intensities of individual elements are somewhat reduced. 

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