What is the unit of measurement that equals the amount of radiation that ionizes one cubic centimeter of air?

The unit of measurement that equals the amount of radiation that ionizes one cubic centimeter of air is the Roentgen. This term specifically quantifies the exposure to X-ray or gamma radiation in terms of ionization in air. One Roentgen is defined as the amount of radiation required to produce a specific amount of charge (in units of coulombs) in a volume of air, and it is a direct measurement of the ionizing effect of radiation.

Other units, although related to radiation, measure different aspects of radiation effects or exposure. For example, the Sievert is used to express the biological effect or risk of radiation on human tissues, while the Rem is a traditional unit of dose equivalent, also concerned with biological effects. The Rad measures the absorbed dose of radiation, focusing on the energy deposited in a material, rather than the ionization in air. Thus, while these other units are important in the field of radiation safety and measurement, they do not specifically define the ionization of air as the Roentgen does.