What happens when carbon dioxide absorbs an IR photon?

Carbon dioxide (CO2) molecules absorb infrared (IR) photons at specific wavelengths. These wavelengths correspond to the energy levels required to excite the different vibrational modes of the molecule. When a CO2 molecule absorbs an IR photon, it gains energy and transitions to a higher vibrational energy level.

Typically, the IR radiation absorbed by CO2 falls within the 15 µm (667 cm-1) and 4.25 µm (2350 cm-1) regions of the electromagnetic spectrum. These bands are due to the asymmetric stretching and bending modes of the CO2 molecule, respectively.

The specific wavelength absorbed depends on various factors, including the temperature, pressure, and concentration of CO2 in the environment. At room temperature and pressure, the strongest absorption bands of CO2 are centered around 15.8 µm (632 cm-1) and 4.26 µm (2349 cm-1).

The ability of CO2 to absorb IR radiation is a crucial aspect of Earth's natural greenhouse effect. When sunlight reaches the Earth's atmosphere, some of the IR radiation emitted by the Earth's surface is absorbed by CO2 and other greenhouse gases. This absorption retains heat within the atmosphere, contributing to the overall warming effect and the regulation of Earth's temperature.

Measuring and monitoring the absorption of IR radiation by CO2 plays a significant role in various fields such as atmospheric science, climate research, greenhouse gas monitoring, and environmental sensing. Scientists use spectroscopic techniques and instruments to study and analyze the spectral features and behavior of CO2 in different environments.