From: "Thomas Smid" <thomas.smid@gmail.com>

Newsgroups: sci.physics.plasma

Subject: Collisional Excitation and Striations in Glow Discharges

Date: 2 Jun 2005 09:56:53 -0700

Organization: http://groups.google.com

Striations in glow discharges are often used as an educational tool for

demonstrating the energy quantization in atoms. However, it has

apparently gone unnoticed so far that the generally accepted cross

sections for collisional excitation of atomic levels lead to mean free

paths for the electrons that are much too large in order to explain the

sharply defined striations (see

http://www.plasmaphysics.org.uk/research/striatn.htm and

http://www.plasmaphysics.org.uk/research/striapot.htm ). It is obvious

that only a resonance type excitation centered at the transition

frequency is able to explain the observed features (see

http://www.plasmaphysics.org.uk/research/reschem.htm ). For a more

detailed treatment of this see chapter 2 of my page

http://www.plasmaphysics.org.uk/papers/airglow2.htm where a resonance

type cross section is shown to be also required to explain the

enhancement of airglow by high power radio waves.

Many phenomena where collisional excitation is relevant need therefore

to be re-intrepreted in this sense (see for instance

http://www.plasmaphysics.org.uk/research/sun.htm for an application to

solar physics).

Thomas