Talk:Glow discharge

message: This article was automatically assessed because at least one WikiProject had rated the article as start, and the rating on other projects was brought up to start class. BetacommandBot 09:49, 10 November 2007 (UTC)
thread_title:  WikiProject class rating

message: * cathode fall (also a main article is needed for this topic)
* generation of carriers
Rainald62 (talk) 09:30, 26 September 2010 (UTC)
thread_title:  Missing content 

message: Professor Howatson says on pages 88-89 of a paperback I picked up years ago: " The arc is characterized by a higher current and a much lower voltage than the glow discharge; the arc voltage is typically less than 50 volts, an order of magnitude lower than the that of the glow discharge. The current density is much higher than in the glow discharge and the cathode region can no longer be distinguished, particularly since the high current density makes the positive column intensely luminous...It is possible to maintain an arc at low pressures (as, for example, in the mercury-arc rectifier) down to a few (microns); the characteristic high current density and low voltage drop are still found."   
And all the other literature I've been reading seems to agree with him that arc discharges and glow discharges are usefully distinct phenomena. --Wtshymanski (talk) 01:17, 7 June 2011 (UTC)
replies: text: Whoops, I guess you're right. The book Plasma chemistry confirms it. Sorry about the confusion. I should've double-checked first. I guess I'll have to change the lede in the flashtube article to direct to the correct place. Thanks for catching that, Wtshymanski, and thanks to Achem as well. Zaereth (talk) 18:02, 7 June 2011 (UTC)
thread_title: Arc vs glow

message: There are several things to consider. It's actually the ions that are the most energetic particles in the plasma. The ions are most energetic near the cathode, while the electrons are most energetic when approaching the anode. The ions make up less than 1% of the plasma and produce all of the emitted light. 
Electrons are far less energetic. The negative field around the cathode tends to always remain constant in size, whereas lengthening the tube will only cause the positive column to grow in length. By the time an electron reaches the end of the negative column, it's energy is almost depleted. It is at this point that most of the electrons move around the positive column, enclosing it inside an electron sheath. From this point, nearly all of the current flow occurs within this electron sheath, bypassing the gas. Contained by the sheath, the plasma in the positive column exchanges electrons neutrally (without taking in much from the cathode or putting much out to the anode), in the form of eddy currents. 
There are three separate ways in which the plasma may produce light, and all three occur to some degree. When the ions and atoms collide, and electron is transferred from one to the other. This causes a photon to be emitted of one of a few very specific wavelengths (spectral lines). This method predominates at low current densities, and is responsible for the pinkish glow. At higher current densities, free-bound transitions tend to occur. This happens when an ion captures a free electron, and a photon of light of any wavelength will be emitted. Areas where the gas appears more whitish (in both the positive and negative column) is where these transitions are occurring. Free-free transitions happen when an electron is accelerated or decelerated by an ion, without being captured by it. This removes some energy from the ion, thus a photon of light is emitted at any wavelength. Free-free transitions increase with increasing energy density (where there is a high concentrations of ions per electrons), and this high energy causes the lower atomic levels to reach saturation very quickly, so the output tends to be centered in the blue to UV portions of the spectrum. Therefore, areas where the gas is blue or purplish is where these free-free transitions are occurring the most. The plasma is literally trying to tear itself apart in opposite directions. I hope that helps. Zaereth (talk) 23:31, 16 June 2017 (UTC)
thread_title: Copied from [[User talk:Chetvorno]]

message: "... longer mean free path allows a charged particle to gain more energy before colliding with another particle ..."
should be?
"... gain more kinetic energy before colliding ..."
— Preceding unsigned comment added by 60.240.12.146 (talk • contribs) 05:52, 11 June 2019 (UTC)
thread_title:  Kinetic?