i want to measure electron density from Halpha or beta stark broadening. i fit gaussian on those lines and determine FWHM 0.6nm. this broadening is only stark broadening. i use Gigosos formula and estimate density 10^16 1/cm^-3. but we know that electron density should be between 10^10-10^14 in our penning ion source. what should i do? how can i determine electron density Except Langmiur prob? because i don not have enough space to use it.
Dear Shahab Salimi,
The best way to deduce the electron number density from the H-alpha hydrogen line is :
Ne(cm^-3) = (FWHM/1.098)^1.4716 x 10^17.
According to your listed FWHM=0.6nm, I calculated the electron density as 4x10^16 cm^-3.
However, it depends on the FWHM, is it only the Stark contribution?
You have to incorporate the Doppler width as well as the Instrumental width.
Anyway, it will not be possible to get the number you mentioned about 10^14, the width has to be decreased by a very large factor; about 100.
If you take width = 0.2 nm ,then the electron density will be 8x10^15.
best wishes,
Aslam
Muhammad Aslam Baig
thanks dr.Aslam. i calculate Doppler width about 0.1nm and instrumental width is 0.2nm. i subtract them from total broadening. thus 0.6 nm is the pure stark broadening that i measure. i calculate electron density as you calculated. but i know my penning ion source does not be in this order of magnitude. what should i do?
Dear Shahab Salimi,
I suggest try to fit the data with Voigt formalism. Using Gaussian and Lorentzian contributions as a free parameters, calculate the Lorentzian contribution. That will be the actual Stark broadening contribution which you may use to calculate the electron number density.
As you mentioned that the total broadening is 0.6 nm , I think it will be almost impossible to use get the electron number density in the range of 10^14 cm^-3.
Are you using Origin software for simulation?
Let me recall, a scientist from France is very good in such matters. I will write his name for you soon.
best wishes,
Aslam
Muhammad Aslam Baig
Dear Dr.Aslam Baig
Actually i fit them with voigt..lorentzian and gaussian profile seperatly.but result did not change more.
Yes...i use origin software to fit profile.
Thanks so much Dear Dr
Dear Shahab Salimi,
As I remarked earlier, from the FWHM you measured, the electron density will be in the range of 10^16. You mentioned that the electron density should be in the range 10^14, it is almost 100 time lower. I have no explanation about it at the moment, may be some one else can help you. Prof. Konjev is an authority in this field, you may contact him for some explanation.
best wishes,
Aslam
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