What Is Krypton?

Krypton is a noble gas element with atomic number 36 and chemical symbol Kr, belonging to Group 18 of the periodic table alongside helium, neon, argon, xenon, and radon. It occurs in trace concentrations in the Earth's atmosphere at approximately 1.14 parts per million by volume and is recovered commercially as a byproduct of the fractional distillation of liquefied air. In engineering contexts, krypton is valued for its chemical inertness, high atomic mass, low thermal conductivity, and the characteristic bright emission spectrum it produces when electrically excited. These properties make it useful in high-intensity discharge lighting, excimer lasers, advanced semiconductor fabrication, and thermal insulation glazing.

Krypton's engineering utility distinguishes it from the lighter noble gases. Its atomic mass of 83.8 daltons and relatively high density allow it to produce more efficient plasma interactions than lighter gases such as argon, while its availability and cost make it preferable to the heavier and less abundant xenon in many industrial processes.

Physical and Spectral Properties

Krypton is colorless, odorless, and electrically insulating under normal conditions. Its outer electron configuration produces a characteristic emission spectrum with strong lines in the visible and near-ultraviolet ranges, making it suitable for spectroscopic calibration and arc-discharge light sources. Thermodynamic and spectral data for krypton, including its ionization energies, vapor pressure, and emission line wavelengths, are documented in the NIST Chemistry WebBook. Krypton's thermal conductivity of approximately 9.5 milliwatts per meter-kelvin at room temperature is significantly lower than that of air, which underlies its use as an insulating fill gas in high-performance glazing units.

Krypton in Lighting and Lasers

When a discharge is driven through krypton gas, the excited atoms emit light across a broad spectrum including visible and ultraviolet wavelengths. High-intensity discharge lamps and halogen incandescent bulbs use krypton or krypton-argon mixtures to increase luminous efficacy and extend filament or electrode lifetimes relative to nitrogen or pure argon fills. Krypton fluoride (KrF) excimer lasers, which emit at 248 nm in the deep ultraviolet, have been applied to semiconductor photolithography, precision micromachining, and refractive eye surgeries. As described in industry resources on noble gas applications, KrF-based excimer sources were the dominant deep-ultraviolet lithography technology before the industry transitioned to ArF (193 nm) systems for the most advanced nodes.

Semiconductor and Industrial Applications

In semiconductor manufacturing, krypton serves primarily as a plasma etch gas constituent. Krypton-fluoride gas mixtures enable high-aspect-ratio etching with ratios exceeding 30:1, which is critical for fabricating advanced 3D NAND memory structures whose layer stacks exceed 300 levels. The high atomic mass of krypton produces efficient momentum transfer in plasma etching, improving material removal rates for vertical feature profiles. Beyond semiconductors, krypton is used to fill the gap between panes in high-performance insulating glass units, providing thermal resistance superior to argon-filled alternatives. In nuclear facilities, radioactive krypton-85, a fission product, serves as a tracer for atmospheric transport studies. The WestAir resource on krypton gas uses details additional industrial contexts where krypton's inertness and density are exploited.

Applications

Krypton has engineering and scientific applications in:

• High-intensity discharge and halogen incandescent lighting systems
• Deep-ultraviolet excimer lasers for semiconductor photolithography
• Plasma etching of high-aspect-ratio features in 3D NAND memory fabrication
• Thermal insulation glazing in energy-efficient building construction
• Ion thruster propellant in spacecraft propulsion systems
• Atmospheric tracer studies using the radioactive isotope krypton-85