Gratitude.
Atomic oxygen (single oxygen atom, O) is the lightest form of oxygen, as it has the lowest mass of the oxygen molecules. Oxygen also exists as a diatomic molecule (O2) and an allotrope called ozone (O3), which have higher masses due to the number of oxygen atoms combined.
Atomic Oxygen (O):
This refers to a single oxygen atom, which is the most fundamental form of oxygen.
Molecular Oxygen (O2):
This is the common form of oxygen we breathe, consisting of two oxygen atoms bonded together.
Ozone (O3):
This is an allotrope of oxygen, meaning it's a different form of the same element, consisting of three oxygen atoms bonded together.
Since atomic oxygen has the fewest oxygen atoms, it naturally has the lowest mass compared to O2 or O3.
Ozone (O3) Lifespan:
Ozone has a relatively long lifespan in the stratosphere, particularly at lower altitudes. For example, at 32 km in the middle latitudes during spring, ozone has a lifetime of about 2 months.
Oxygen (O) Lifespan:
Atomic oxygen, on the other hand, has a much shorter lifespan. At the same altitude, its lifetime is about 4/100ths of a second.
Ozone-Oxygen Cycle:
The ozone-oxygen cycle involves the rapid exchange between atomic oxygen (O) and ozone (O3). UV radiation can split molecular oxygen (O2) into atomic oxygen (O), which then reacts with O2 to form ozone (O3). Ozone can also be photolyzed by UV radiation, creating atomic oxygen again, which can then react with O3 to reform O2.
Dominant Form:
The partitioning of odd oxygen (Ox) between ozone and atomic oxygen favors ozone in the lower stratosphere. This means that a much larger proportion of odd oxygen exists as ozone than as atomic oxygen, especially in the lower stratosphere.
Recombination:
Atomic oxygen has a high energy and reactivity. When it encounters another oxygen atom, they can combine to form O2. This process releases energy, contributing to the heating of the atmosphere.
Ozone Formation:
Atomic oxygen can also react with molecular oxygen (O2) to form ozone (O3). Ozone plays a significant role in absorbing harmful UV radiation.
Other Reactions:
Atomic oxygen can react with various other molecules in the atmosphere, like nitrogen (N2), water (H2O), and carbon dioxide (CO2), forming different compounds.
UV light below 240nm (peak 185nm) creates ozone (O₃) through a process called photolysis, where UV light breaks down dioxygen molecules (O₂) into single atomic oxygen atoms (O). These single oxygen atoms then react with other oxygen molecules to form ozone (O₃). Specifically, UV-C light with wavelengths shorter than 240 nm can cause this photolysis.
UV light with wavelengths between 240-280 nm, (peak 254 nm) breaks down ozone (O₃) into dioxygen molecules (O₂) and atomic oxygen atoms (O). 280nm does not have the energy potential to break apart the stable bond of (O₂) into enough (O) to make (O₃)
At ground level, atomic oxygen (single oxygen atoms) has a very short lifespan. This is because it's highly reactive and quickly combines with other molecules to form stable diatomic oxygen (O2) or other compounds. While the exact timeframe varies depending on the specific circumstances, its lifespan is typically measured in nanoseconds or picoseconds.