When we are growing up and learning about the world, there are moments when a topic or idea really catches our attention. Perhaps it is while reading a book or during a lecture given by a good teacher. For me, one of those moments occurred during my junior year of high school in Mr. Brooks’s chemistry class. We were learning about the structure of the atom, and Mr. Brooks did a demonstration for us. He turned off the lights in the classroom and turned on a hydrogen discharge tube. The tube glowed with a pink light. Then Mr. Brooks put a prism in front of the glowing discharge tube, and several vertical lines of light appeared on the chalk board behind the prism.
At the time, I didn’t really understand that the voltage applied across the discharge tube was exciting the electrons around the hydrogen atoms and that the lines formed as the pink light passed through the prism were characteristic wavelengths of light being emitted as the electrons around the hydrogen atoms returned to lower energy levels. But I clearly remember the intense curiosity I felt about the phenomenon I was witnessing. It is, therefore, with some nostalgia that I announce the addition of the National Institute of Standards and Technology’s (NIST) atomic spectra database to Wolfram|Alpha.
Investigation of atomic spectra contributed significantly to our understanding of atomic structure and are described by the Rydberg formula. Furthermore, atomic spectra are used by astronomers to classify and determine the composition of stars. Today, the NIST database has become the most comprehensive and reliable set of data for atomic spectra and includes information about spectral lines and atomic energy levels associated with many elements and ions. All of this data can now be found in Wolfram|Alpha, including that visible hydrogen spectrum I was so curious about in high school:
And, while I didn’t realize it at the time, there are far more emission lines than what can be seen by the human eye in the full ”hydrogen atomic spectrum”. Similar to the visible spectrum, Wolfram|Alpha plots the full atomic spectrum for all the elements and ions in the NIST database, including labels identifying the electromagnetic region in which they reside. Wolfram|Alpha also allows the user to “zoom in” to a particular region in a subpod and toggle between plotting the lines by wavelength, frequency or energy. And with the “Show oscillator strength” button, a plot of the oscillator strengths for the spectral lines appears, indicating which transitions are more likely to be detected. Wolfram|Alpha also gives more detailed information about each line in a table (sorted by the electromagnetic region in which they reside), showing the corresponding energy levels, oscillator strength and transition probability.
Perhaps you want to know more about the energy levels making up the spectrum you are studying. Try something like “sodium II energy levels”, and Wolfram|Alpha displays a table of the energy levels for the first ionization state of sodium sorted by wavenumber, energy or frequency. The corresponding electron configurations and the term symbol to which they belong are shown.
As the breadth of scientific and technical knowledge contained in Wolfram|Alpha grows, it is becoming a reference for a wider range of people. With the addition of atomic spectra data, those people now include the high school student learning about the structure of an atom or an astronomer trying to discover the composition of a star. Who knows—maybe Mr. Brooks will reference Wolfram|Alpha the next time he demonstrates the visible hydrogen spectrum to a new batch of curious students.