Atomic spectrum
A neon lamp does not emit a continuous rainbow of colors. Instead, its atoms emit light at specific wavelengths when electrons make quantized transitions between allowed energy levels. A USB spectrometer separates the lamp’s light by wavelength, making these discrete emission lines directly visible and allowing them to be compared with the known atomic spectrum of neon.
What you are seeing
The four aligned displays cover the same 450–700 nm wavelength range. At the top is the full visible spectrum. Below it, the live spectrometer image shows that the neon lamp emits only selected wavelengths. The next display extracts those detected wavelengths as discrete lines, and the final display shows the known strong neon emission lines from NIST for direct comparison.
Bright NIST reference lines were observed by the spectrometer during validation. Faint lines are additional NIST lines that were not observed. This is because not every reference line is detectable: lamp conditions and the spectrometer’s sensitivity and resolution (2–3 nm) limit which lines can be detected.
You may see lines appear or disappear, more so at higher detection sensitivity. This is because the raw detector data contain noise that may move a line’s measured signal above or below the detection threshold.
Visible spectrum
Live spectrometer image
Detected spectral features
NIST strong Ne I reference lines
What is quantum here?
Neon is a noble gas with atomic number 10: a neutral neon atom has 10 protons in its nucleus and 10 electrons surrounding it. Inside the lamp, an electric discharge accelerates free electrons, which collide with neon atoms and can transfer enough energy to push one of their electrons into a higher, excited energy level. Those excited states are temporary. Quantum mechanics allows the electron to return to a lower energy level, and when it does, the atom emits a photon whose energy exactly matches the difference between the two levels.
Because photon energy determines wavelength, each transition produces light at a particular wavelength. Neon has many possible transitions, so its light contains many distinct spectral lines rather than a continuous spread of colors.
The spectrometer separates this light by wavelength and projects it onto a camera sensor, where different wavelengths appear at different positions. From that live detector image, the experiment identifies the spectral lines produced by the neon lamp. Their distinctive pattern is a directly observable consequence of the quantized energy structure of neon atoms.
About the setup
- Location
- Bladel, The Netherlands
- Status
- Connected
- Spectrometer
- Thunder Optics Mini USB Spectrometer
- Light source
- Schiefer T14×30 neon discharge lamp
- Wavelength range used
- 450–700 nm
- Approximate spectral resolution
- 2–3 nm