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Problem with Doppler Broadening |
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| Jun6-09, 01:48 PM | #1 |
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Problem with Doppler Broadening
Hello,
I would like to know how to calculate the broadening of the spectral lines caused by the Doppler effect for the Lyman, Balmer and Paschen series. To be more concrete, I would like to know the broadening of the alpha transitions. The equations I use are the following but i don't know if I am doing something wrong. [tex]\Delta \nu &=&2\frac{\nu _{o}}{c}\sqrt{\frac{2KT}{m}\ln \left( 2\right) }[/tex] I calculate [tex]\nu _{o}[/tex] Doing the following: [tex]E_{n}-E_{n^{\prime }} &=&\left[ \frac{1}{\left( n^{\prime }\right) ^{2}}- \frac{1}{\left( n\right) ^{2}}\right] \frac{Z^{2}e^{4}\mu }{2\left( 4\pi \varepsilon _{o}\right) ^{2}\hbar ^{2}}=-h\nu _{o}[/tex] [tex]\nu _{o} &=&-\frac{Z^{2}e^{4}\mu }{4\pi \left( 4\pi \varepsilon _{o}\right) ^{2}\hbar ^{3}}\left[ \frac{1}{\left( n^{\prime }\right) ^{2}}-\frac{1}{ \left( n\right) ^{2}}\right][/tex] For T=300K we have: [tex]\nu _{o} &\approx &-\frac{e^{4}m_{e}}{4\pi \left( 4\pi \varepsilon _{o}\right) ^{2}\hbar ^{3}}\left[ \frac{1}{\left( n^{\prime }\right) ^{2}}- \frac{1}{\left( n\right) ^{2}}\right] \approx -3.288953357\cdot 10^{15}\left[ \frac{1}{\left( n^{\prime }\right) ^{2}}-\frac{1}{\left( n\right) ^{2}} \right] \ \ Hz[/tex] SO: [tex]\Delta \nu &=&2\frac{\nu _{o}}{c}\sqrt{\frac{2KT}{m}\ln \left( 2\right) } \approx -0.000040625\cdot 10^{15}\left[ \frac{1}{\left( n^{\prime }\right) ^{2}}-\frac{1}{\left( n\right) ^{2}}\right] \ \ Hz[/tex] Finally, the following numbers are obtained: [tex]\begin{tabular}{|l|l|} \hline $Line$ & $\Delta \nu \ (GHz)$ \\ \hline\hline $\alpha \ LYMAN$ & $ 30.4685$ \\ \hline $\alpha \ BALMER$ & $ 5.64236$ \\ \hline $\alpha \ PASCHEN$ & $ 1.974826$ \\ \hline \end{tabular}[/tex] Unfortunatelly, I can't find any book to confirm this results, that is why I am posting this. What do you say? Am I doing anything wrong? Eliot. |
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| alpha, broadening, doppler, lyman, paschen |
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