Photo-desorption – Definition & Detailed Explanation – Astrochemistry Glossary

I. What is Photo-desorption?

Photo-desorption is a process in which molecules are ejected from a surface due to the absorption of photons. This phenomenon is commonly observed in astrophysical environments, where the interaction between radiation and solid surfaces can lead to the release of molecules into the gas phase. Photo-desorption plays a crucial role in astrochemistry, as it contributes to the chemical composition of interstellar and circumstellar regions.

II. How does Photo-desorption occur?

Photo-desorption occurs when a photon is absorbed by a molecule on a solid surface, causing it to gain enough energy to overcome the binding forces holding it in place. This energy transfer can lead to the molecule being ejected from the surface and entering the gas phase. The process is highly dependent on the wavelength and intensity of the incident radiation, as well as the properties of the surface and the molecule involved.

III. What are the implications of Photo-desorption in Astrochemistry?

Photo-desorption has significant implications for astrochemistry, as it can influence the chemical evolution of interstellar and circumstellar environments. By releasing molecules from solid surfaces, photo-desorption contributes to the gas-phase chemistry of these regions, leading to the formation of complex organic molecules and other chemical species. Understanding the mechanisms and rates of photo-desorption is essential for accurately modeling the chemical processes occurring in space.

IV. What are some examples of Photo-desorption in space?

Photo-desorption has been observed in a variety of astrophysical environments, including interstellar clouds, protoplanetary disks, and the surfaces of comets and asteroids. In interstellar clouds, the absorption of ultraviolet radiation from nearby stars can lead to the release of molecules from dust grains, enriching the gas phase with volatile species. On comets and asteroids, the sublimation of volatile compounds due to solar radiation can also result in photo-desorption processes.

V. How is Photo-desorption studied in the laboratory?

In the laboratory, photo-desorption processes can be studied using a variety of experimental techniques. One common approach is to irradiate a solid surface with a laser or other light source and monitor the desorption of molecules using mass spectrometry or other analytical methods. By varying the wavelength, intensity, and duration of the radiation, researchers can investigate the mechanisms and kinetics of photo-desorption under controlled conditions.

VI. What are the challenges in studying Photo-desorption?

Studying photo-desorption presents several challenges due to the complexity of the processes involved. One major challenge is the need to accurately simulate the conditions of astrophysical environments in the laboratory, including the composition of the solid surfaces and the properties of the incident radiation. Additionally, the low desorption yields and short timescales of photo-desorption events can make it difficult to detect and quantify the ejected molecules. Developing new experimental techniques and theoretical models is essential for advancing our understanding of photo-desorption in astrochemistry.