NexGen Spectrum Tube, Water Vapor

Demonstrate water vapor's molecular emission in the classroom

The NexGen Spectrum Tube, Water Vapor contains water vapor (H2O) and runs on the NexGen Spectrum Tube Power Supply. When energized, it produces a pinkish-white glow. Through a spectroscope, it reveals a complex molecular band spectrum from both OH radicals and intact H2O molecules, spread across multiple regions of the visible range.

Water vapor's spectrum is complex because a three-atom molecule has many vibrational and rotational modes that broaden emission into overlapping bands. That stands in sharp contrast to hydrogen gas, which produces four clean Balmer lines, even though both tubes contain hydrogen. Showing both in the same session makes the point clearly: it's not just which elements are present but how atoms are bonded that determines a substance's optical signature. Water vapor also connects to real-world topics including atmospheric absorption, greenhouse gas science, and the spectroscopic study of exoplanet atmospheres.

Why Teachers Love It

• A Natural Companion to the Hydrogen Tube – Both tubes contain hydrogen, yet their spectra look nothing alike. Running both in the same lab gives students a direct, side-by-side demonstration that bonding and molecular structure fundamentally change an element's emission pattern.

• Built for Long-Term Classroom Use – No internal electrodes means the tube resists the wear that shortens conventional spectrum tube life. A hard polymer shell protects the glass from everyday bumps and drops.

• Continuous Use with the NexGen Power Supply – No timing restrictions. Students work at their own pace comparing the water vapor band spectrum to other molecular and atomic spectra without a countdown.