Gvalues

Gvalues is a term used in radiation chemistry to describe chemical yields measured in radiolysis. It denotes the number of molecules formed or destroyed per 100 eV of energy absorbed by a substance under irradiation. The concept is applied to both primary yields, which reflect immediate products after energy deposition, and observed yields, which can change over time as reactive intermediates recombine or react further.

Calculation of a G-value follows the idea that G_p equals the change in the number of molecules of product p divided by the energy absorbed, scaled to 100 eV. In practice, G-values are reported as molecules per 100 eV and are often tabulated for common solvents and radioproducts under different radiation types (electrons, gamma rays, heavy ions) and environmental conditions. Because radiolysis involves complex networks of radical and molecular reactions, a single G-value may be an average over competing pathways and time.

G-values depend on several factors, including the quality of radiation (linear energy transfer or LET), temperature, solvent, and the presence of scavengers or stabilizers. High-LET radiation and certain chemical conditions can alter yields by affecting radical lifetimes and reaction pathways.

Applications of G-values span modeling radiolysis in water and organic solvents, estimating yields of hydrogen, hydrogen peroxide, radicals, and other products, and informing radiation processing design, dosimetry, and radiobiology. While useful, G-values are most informative when used within kinetic models that account for time-dependent chemistry and environmental context.