Low pressure discharge

Because of the relatively high population of the u" = 0 level the v" = 0 progression is likely to be prominent in the absorption spectrum. In emission the relative populations of the i/ levels depend on the method of excitation. In a low-pressure discharge, in which there are not many collisions to provide a channel for vibrational deactivation, the populations may be somewhat random. However, higher pressure may result in most of the molecules being in the v = 0 state and the v = 0 progression being prominent. 

Fluorescent lamps are termed a low-pressure discharge lamp. An electric current passes through mer-... 

Low-pressure discharges tend to produce much more intense chemiluminescence from alkenes than from alkanes. This has been attributed to the addition of N to the double bond, as illustrated for ethylene,... 

Rutscher, A., "Progress in Electron Kinetics of Low Pressure Discharges and Related Phenomena", presented at the 13 International Congress on Phenomena in Ionized Gases, East Berlin, GDR, September, 1977. 

The effects of various added gases on the rate of formation of ozone in a flow system have been studied at 1849 A. with light from a mercury-rare gas low pressure discharge (92). In a 30-mm. diameter cylindrical quartz reaction vessel at a flow rate of 2.0 l./min. at 1-atm. total pressure and 0.25-atm. oxygen pressure, the relative rates of ozone formation were ... 

So far we have considered an idealized model possessing most of the significant properties of the plasma of intense low pressure discharges. The choice of a simple... 

The main subject of this review were the theoretical aspects of plasma CVD processes. The applications will be discussed in another paper. The results so far obtained show that the plasma of intense low pressure discharges offers new techniques of crystal growth. There are also other problems and tasks, which are just as important and which merit a more thorough study. These include for example, the application of plasma to thin film technology, the importance of which may be expected to increase in ihe future. The purification of materials by plasma transport can find practical uses, and many other applications will certainly be found. 

The effect of an intense low pressure discharge in nitrogen is threefold ... 

Explorations are being undertaken or planned on low pressure discharges in H2, where a detection sensitivity of 10-7 atm. can be obtained, and on chemical lasers, piston engines and real jet engine combustors. 

A group of transitions with the same value of A.v is referred to as a sequence. Because of the population requirements long sequences are observed mostly in emission. For example, sequences of five or six members are observed in the C37/ - S7/ band system of N2 in emission in the visible and near-ultraviolet from a low-pressure discharge in nitrogen gas. The vibration wavenumber coe is high (2047.18 cm-1) in the C state and equilibrium population of the vibrational levels is not achieved before emission. 

Calibration lines from low-pressure discharge lamps. The wavelengths in nm are given in air and die stronger lines are indicated with a plus sign (+). 

The material deposition that occurs in the low-pressure electrical discharge has been discussed under various terminologies such as plasma polymerization (PP), plasma-enhanced chemical vapor deposition (PECVD), plasma-assisted chemical vapor deposition (PACVD), plasma chemical vapor deposition (PCVD), and so forth [1]. However, none of these terminologies seems to represent the phenomenon adequately. The plasma aspect in the low-pressure discharge is remote, although it plays a key role in creating the environment from which material deposition occurs to the extent that no chemical reaction occurs without the plasma. In this sense, PECVD and PACVD could be out of the context in many cases in which nothing happens without plasma. In such cases, PP or PCVD would describe the phenomenon better. If the substrate was not heated substantially above the ambient temperature, the use of PECVD or PACVD should be avoided. 

The halogens CI2, Br2, and I2 can also be oxidized to cationic species. Examples include the diatomic ions Bt2 and 12 (Cl2 has been characterized in low-pressure discharge tubes but is much less stable), and 12" dimerizes into 14 ... 

In a conventional PE apparatus the spectrum is obtained by scanning the electron kinetic energy at a fixed wavelength of photons. Most frequently applied photon sources are Hel and Hell radiation produced by low-pressure discharge through helium. 

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