Certainly! There are several examples of molecules that absorb infrared (IR) light but do not emit it. These molecules are known as infrared absorbers or vibrational absorbers. When exposed to infrared radiation, they can absorb specific wavelengths of light, causing their constituent atoms to undergo vibrational transitions between different energy levels. However, these molecules do not typically emit infrared light as a result of these transitions. Here are a few examples:
Carbon dioxide (CO2): Carbon dioxide is a well-known molecule that absorbs infrared radiation in specific vibrational modes. It absorbs infrared light in the range of approximately 2.7 to 3.3 micrometers (µm), which is part of the mid-infrared region. This absorption is responsible for the greenhouse effect, as CO2 traps heat in the Earth's atmosphere.
Water (H2O): Water molecules also absorb infrared light in certain vibrational modes. They absorb light in the mid-infrared region around 6.3 µm and 2.7 µm, among other ranges. This is why water vapor in the atmosphere can contribute to the overall absorption of infrared radiation.
Methane (CH4): Methane is another molecule that absorbs infrared light. It absorbs light in the range of approximately 3.3 to 3.4 µm, which is part of the mid-infrared region. Methane is a greenhouse gas and is known to contribute to the trapping of heat in the Earth's atmosphere.
Nitrous oxide (N2O): Nitrous oxide, also known as laughing gas, absorbs infrared light in specific vibrational modes. It absorbs light in the mid-infrared region around 7.8 to 8.2 µm. Nitrous oxide is a greenhouse gas and plays a role in the Earth's climate system.
These are just a few examples of molecules that absorb infrared light but do not emit it significantly. These molecules exhibit selective absorption of specific infrared wavelengths due to the unique vibrational modes they possess.