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