Electric discharge emission from

Electrically excited emission from OH itself provides an appropriate source, and individual lines isolated by a low-resolution monochromator from a low-intensity electric discharge through HjO vapour are quite suitable for photoelectric work in flames. Kaskan has exploited this method with a d.c. discharge source to detect [OH] overshoots in both fuel-rich and fuel-lean Hj-air flat flames. Absolute concentrations of OH were derived from independently determined spectroscopic parameters for the transition and the approximation that only the line centres were involved. The rate of decay of [OH] was measured in the... 

A third pumping method (Fig. Ic) uses an electrical discharge in a mixture of gases. It relies on electronic excitation of the first component of the gas mixture, so that those atoms are raised to an upper energy level. The two components are chosen so that there can be a resonant transfer of energy by collisions from the upper level of the first component to level 3 of the second component. Because there are no atoms in level 2, this produces a population inversion between level 3 and level 2. After laser emission, the atoms in the second component return to the ground state by collisions. 

Emission of light accompanying the passage of intense sound waves through a liquid and arising from electrical discharges in the residual gas of cavities formed by the acoustic energy in the liquid. 

Ultraviolet Spectra. The first direct evidence for the existence of gas phase monomeric silicon difluoride resulted from observation of emission spectra of the molecule in an electric discharge through SiF4 9 The emission band system was subsequently extended 60however, both of these investigations are now thought... 

The condition for observing induced emission is that the population of the first singlet state Si is larger than that of So, which is far from the case at room temperature because of the Boltzmann distribution (see above). An inversion of population (i.e. NSi > Nso) is thus required. For a four-level system inversion can be achieved using optical pumping by an intense light source (flash lamps or lasers) dye lasers work in this way. Alternatively, electrical discharge in a gas (gas lasers, copper vapor lasers) can be used. 

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