Dear Debashish,
You may read the following:

1. Glow discharge processes by Brian Chapman.

2. http://www.glow-
discharge.com/Index.php?Physical_background:Glow_Discharges:GD_Processes

3.http://dx.doi.org/10.1016/0257-8972(95)08330-8

4. linkinghub.elsevier.com/retrieve/pii/S0042207X00002578

5. Emission spectroscopy of atmospheric pressure plasmas for bio-medical
and  environmental applications. Z. Machala et al . Journal of Molecular
Spectroscopy 243 (2007) 194–201

Thank you

Ranjini

On Thu, Sep 9, 2010 at 1:43 AM, Gareth Jenkins wrote:

> If you have a spectrometer you can check that the emission lines match that
> of Ar using the NIST database: http://www.nist.gov/physlab/data/asd.cfm
>
> Pressure will affect the mean free
> path and hence the energies achieved between collisions. Different energies
> will access different transition states which ultimately affects the
> emission observed.
>
> On 8 September 2010 14:39, Ranjini Menon  wrote:
>
> > Dear Debashish,
> >
> > when you vary the power or pressure in the system, then the number of
> > charge particles/ or excited particles and their energy level varies.
> shift
> > in color is due to change in available energy levels.
> >
> > what sort of plasma system do you have? RF CCP?
> >
> > thanks