This a reviewer question on an article of mine. The question was: "Even though the carbon is a major element, why its intensity of C247 nm much lower than that of Na 588, 589 nm lines (minor element) in the observed LIBS spectrum"?
My answer is; "Neutral carbon is usually not easily detected because of its low transition probability values compared to sodium. Moreover, carbon has much higher ionisation potential 11.26 ev and melting point 3773K compared to sodium (5.139 EV, 371K). So sodium is more easy to be represented in LIBS spectrum with much lower laser beam intensities than carbon."
Do you agree with my answer or do you have any other suggestions?
Our friend Dr. Gianpiero Colonna , suggest for me to focus on the transition probabilitie and excited states differences.
Yes Prof. Walid, you are absolutely correct. transition probability and population of atoms are the two important parameters which decide the intensity of any spectral line...since m.p is too high it is not easy to get more population. Ionization potential will come in picture if one study the ionic line intensity...
sodium lines appear quit strongly even it if is present just a trace whereas the carbon line at 247 is quite tricky to observe. The transition probabilities of C and Na lines needs to be considered.
Walid I endorse your answer.
Aslam
Thanks for your valuable comments I have received till now. I appreciate all the contributions.
Dear Prof. Walid Tawfik,
Your question has really stimulated a good discussion and we got good information pertaining to the relative intensities of Carbon and Sodium. There is another aspect worth noting, it is the detection efficiency of the detectors which is normally much lower at 247 nm as compared to that at 590 nm.
I think, melting point as well the ionization potentials of carbon and sodium are also contributing towards the lower detection limit of carbon.
I hope you will keep on floating such interesting questions. I am confident you know the answers very well but such discussion are very illuminating for other researchers like me who are just entering and learning the field of LIBS.
Best regards,
Aslam
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