Matrix Isolated Molecules

To carry out Professor McMahon's research, chemical species containing radicals or carbenes are frozen in argon to keep them from reacting with each other. The frozen argon is referred to as a "matrix". Argon is a gas at room temperature. It is called a noble gas, or inert, because of its low reactivity. By cooling argon gas to 10 Kelvin (negative 263 degrees Celsius), one can surround each reactive molecule with many argon atoms that will not react with it. This isolates the reactive molecules so that they cannot combine with each other.

Jello With Fruit

The matrix can be imagined like jello with fruit in it. The jello represents the frozen argon and the fruit represents the reactive chemical species. The fruit (reactive species) is stuck in the jello (argon) and cannot get to any other neighboring fruit pieces.