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Diffstat (limited to 'spectr.tex')
| -rw-r--r-- | spectr.tex | 13 |
1 files changed, 8 insertions, 5 deletions
@@ -10,7 +10,7 @@ The observation of discrete lines in the emission spectra of atomic gases gives insight into the quantum nature of atoms. Classical electrodynamics cannot explain the existence - of these discrete lines, whose energy (or wavelengths) are + of these discrete lines, whose energies (or wavelengths) are given by characteristic values for specific atoms. These emission lines are so fundamental that they are used to identify atomic elements in objects, such as in identifying @@ -81,7 +81,8 @@ state $n_2$ as follows: Fig.~\ref{Hspec.fig} shows the energy levels of hydrogen, and indicates a large number of observed transitions, grouped into series with the common electron final state. Emitted photon frequencies -span the spectrum from the UV (UltraViolet) to the IR (InfraRed). Among all the series only the +span the spectrum from the UV (UltraViolet) to the IR (InfraRed). Among all +the series, only the Balmer series, corresponding to $n_2$ = 2, has its transitions in the visible part of the spectrum. Moreover, from all the possible transitions, we will be able to observe and measure only the following four lines: $n_1=6 \rightarrow 2$, $5 \rightarrow 2$, $4 \rightarrow 2$, @@ -123,12 +124,14 @@ that the $3s$ valence electron experiences the electric field potential similar to that of a hydrogen atom, given by the Eq.~\ref{Hlevels_inf}. -However, there is an important variation of the energy spectrum of alkali metals, related to the +However, there is an important variation of the energy spectrum of alkali +metals, which is related to the electron angular momentum $l$. In hydrogen the energy levels with same principle quantum number $n$ but different electron angular momentum $l=0, 1, \cdots (n-1)$ are degenerate. For Na and others the levels with different values of $l$ are shifted with respect to each other. This is mainly due to the interaction of the unpaired electrons with the electrons of the closed shells. For example, the -orbits of the electron with large angular momentum value $l$ is far above closed shell, and thus +orbits of the electron with large angular momentum values $l$ are far +above the closed shell, and thus their energies are basically the same as for the hydrogen atom. An electron with smaller $l$ spends more time closer to the nucleus, and ``feels'' stronger bounding electrostatic potential. As a result the corresponding energy levels are pulled down compared to those of hydrogen, and the states with the @@ -215,7 +218,7 @@ forbidden. The strongest allowed optical transitions are shown in Fig. \ref{natr \begin{figure} \includegraphics[height=\columnwidth]{./pdf_figs/natrans} \caption{\label{natrns}Transitions for Na. The wavelengths of selected transition are shown in {\AA}. -Note, that $p$ state is now shown in two columns, one referred to as $P_{1/2}$ and the other as +Note that $p$ state is now shown in two columns, one referred to as $P_{1/2}$ and the other as $P_{3/2}$. The small difference between their energy levels is the ``fine structure''.} \end{figure} %\begin{figure} |