What are Spectral Emission Lines?

Light Notes

Spectral emission lines are unique sets of spectral lines that serve as the fingerprints of chemical and molecular species, playing a crucial role in various scientific fields such as optics, photonics, chemistry, and physics. Experts in various industries use these spectral emissions to study the elemental and molecular compositions of a near-limitless range of substances. They can be used for relatively mundane reasons – such as identifying the chemistry of any translucent medium – but are more usually associated with the study of distant astronomical bodies, like clouds of interstellar gas or stars. So, what exactly are emission lines, and how can we detect them? 

The Science Behind Spectral Emission Lines

Spectral emission lines occur when atoms or molecules transition from higher to lower energy states, emitting specific wavelengths of light in the process. These spectral lines are unique to each chemical and molecular species, allowing for their identification based on their respective emission or absorption spectrum. The spectral lines of elements cover the visible, near-IR, mid-wave IR, and long-wave IR wavelength regions, making them highly useful for various applications.

One of the most well-known examples of spectral emission lines is the Balmer series for hydrogen. These lines occur when an electron transitions from a higher energy level (n ≥ 3) to the second energy level (n = 2) in a hydrogen atom. The Balmer series spectral lines fall within the visible region of the electromagnetic spectrum, with the Hα, Hβ, Hγ, and Hδ lines corresponding to wavelengths of approximately 656 nm, 486 nm, 434 nm, and 410 nm, respectively. Given it is so well-defined and easily observable in the visible range, the Balmer series is directly applicable to various scientific fields – including astronomy.

Applications of Spectral Emission Line Detection

The detection of spectral emission lines has multiple applications in fields like remote sensing, environmental monitoring, and IR sensing. As mentioned, the Balmer series helps astronomers to understand the composition, motion, and temperature of celestial objects. Hα (656 nm) is particularly important in studying star formation regions and ionized hydrogen (H II) regions in galaxies, as well as the kinematics of stars and gas in the Milky Way. Additionally, the Balmer lines are used to determine the surface temperatures of stars, as they exhibit different line strengths depending on the star’s temperature.

Back on earth, analytical instruments such as PAS gas detection systems – although not strictly based on spectral emission lines – utilize gas absorption at specific wavelengths for detecting emission or absorption lines. This is vital for industries requiring precise monitoring of elemental and molecular species, leading to improved environmental and safety practices.

How We Serve the Market

At Iridian Spectral Technologies, we supply leading OEMs with filter technology for an array of spectral line detection applications. These include environmental monitoring instrumentation, supporting research, prototype, and replacement markets. Our commitment to customer success, along with decades of filter design and manufacturing experience, allows us to provide unparalleled support throughout a product’s life cycle. From initial prototyping to high-volume manufacturing, our automated production facility ensures cost-effective optical solutions for any application.

We offer a range of band-pass and edge-pass filters in various wavelength regions, including visible, near-IR, mid-wave IR, and long-wave IR. Our new custom filters in the 10-15 um range cater to specific requirements in the detection of spectral emission lines. The bandwidths available for UV-visible spectral line emission filters and mid-longwave IR emission and absorption line filters enable the optimization of detection for various applications.

Understanding and utilizing spectral emission lines is essential for various applications, from environmental monitoring to research and development. Our specialized optical filters and solutions offer a reliable means for detecting these unique spectral lines, supporting the success of their customers in diverse industries. Explore our offerings to find the perfect optical filter solution for your specific needs.

References and further information

  1. https://www.britannica.com/science/Balmer-series 
  2. H Balmer lines in terrestrial aurora: Historical record and new observations by OSIRIS on Odin R. L. Gattinger, A. Egeland, A. E. Bourassa, N. D. Lloyd, D. A. Degenstein, J. Stegman, E. J. Llewellyn First published: 09 September 2010 https://doi.org/10.1029/2010JA015338

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